It is obvious that the main tasks of seismic exploration with the existing level of equipment are:
1. Increasing the resolution of the method;
2. Possibility of predicting the lithological composition of the medium.
In the last 3 decades, the most powerful industry of seismic exploration of oil and gas fields has been created in the world, the basis of which is the common depth point method (CDP). However, with the improvement and development of CDP technology, the unacceptability of this method for solving detailed structural problems and predicting the composition of the medium becomes more and more clearly manifested. The reasons for this situation are the high integrity of the obtained (resulting) data (sections), incorrect and, as a result, incorrect in most cases determination of effective and average velocities.
The introduction of seismic exploration in complex environments of ore and oil regions requires a fundamentally new approach, especially at the stage of machine processing and interpretation. Among the new developing areas, one of the most promising is the idea of ​​a controlled local analysis of the kinematic and dynamic characteristics of a seismic wave field. On its basis, the development of a method for differential processing of materials in complex media is being developed. The basis of the method of differential seismic survey (DMS) is local transformations of the initial seismic data on small bases - differential in relation to the integral transformations in the CDP. The use of small bases, leading to a more accurate description of the hodograph curve, on the one hand, the selection of waves in the direction of arrival, which allows processing complexly interfering wave fields, on the other hand, creates the prerequisites for using the differential method in complex seismogeological conditions, increases its resolution and accuracy of structural constructions ( Fig. 1, 3). An important advantage of the MDS is its high parametric equipment, which makes it possible to obtain the petrophysical characteristics of the section - the basis for determining the material composition of the medium.
Wide testing in various regions of Russia has shown that MDS significantly exceeds the capabilities of CMP and is an alternative to the latter in the study of complex environments.
The first result of differential processing of seismic data is a deep structural section of the MDS (S is a section), which reflects the nature of the distribution of reflective elements (areas, boundaries, points) in the studied medium.
In addition to structural constructions, MDS has the ability to analyze the kinematic and dynamic characteristics of seismic waves (parameters), which in turn allows you to proceed to the assessment of the petrophysical properties of the geological section.
To construct a section of quasi-acoustic stiffness (A - section), the values ​​of the amplitudes of the signals reflected on the seismic elements are used. The obtained A-sections are used in the process of geological interpretation to identify contrasting geological objects (“bright spot”), zones of tectonic faults, boundaries of large geological blocks and other geological factors.
The quasi-attenuation parameter (F) is a function of the frequency of the received seismic signal and is used to identify zones of high and low consolidation of rocks, zones of high attenuation (“dark spot”).
The sections of average and interval velocities (V, I - sections), which characterize the petro-density and lithological differences of large regional blocks, carry their own petrophysical load.

DIFFERENTIAL PROCESSING SCHEME:

INITIAL DATA (MULTIPLE OVERLAPS)

PRELIMINARY PROCESSING

DIFFERENTIAL PARAMETERIZATION OF SEISMOGRAMS

EDITING PARAMETERS (A, F, V, D)

DEEP SEISMIC SECTIONS

PETROPHYSICAL PARAMETER MAP (S, A, F, V, I, P, L)

TRANSFORMATION AND SYNTHESIS OF PARAMETER MAP (IMAGE FORMATION OF GEOLOGICAL OBJECTS)

PHYSICAL AND GEOLOGICAL MODEL OF THE ENVIRONMENT

Petrophysical parameters
S - structural, A - quasi-rigidity, F - quasi-absorption, V - average velocity,
I - interval velocity, P - quasi-density, L - local parameters

Time section of CDP after migration

Deep section of MDS

Rice. 1 COMPARISON OF THE EFFICIENCY OF MOGT AND MDS
Western Siberia, 1999

Time section of CDP after migration

Deep section of MDS

Rice. 3 COMPARISON OF THE EFFICIENCY OF MOGT AND MDS
North Karelia, 1998

Figures 4-10 show typical examples of MDS processing in various geological conditions.

Time section of CDP

Quasi-absorption section Deep section of MDS

Section of average speeds

Rice. 4 Differential processing of seismic data under conditions
complex dislocations of rocks. Profile 10. Western Siberia

Differential processing made it possible to decipher the complex wave field in the western part of the seismic section. According to the MDS data, an overthrust was found, in the area of ​​which there is a “collapse” of the productive complex (PK PK 2400-5500). As a result of a complex interpretation of the sections of petrophysical characteristics (S, A, F, V), zones of increased permeability were identified.

Deep section of MDS Time section of CDP

Quasi-acoustic stiffness section Quasi-absorption section

Section of average speeds Section of interval velocities

Rice. 5 Special processing of seismic data in searches
hydrocarbons. Kaliningrad region

Special computer processing makes it possible to obtain a series of parametric sections (maps of parameters). Each parametric map characterizes certain physical properties of the medium. The synthesis of parameters serves as the basis for the formation of the "image" of an oil (gas) facility. The result of a comprehensive interpretation is a Physical-Geological Model of the environment with a forecast for hydrocarbon deposits.

Rice. 6 Differential processing of seismic data
in search of copper-nickel ores. Kola Peninsula

As a result of special processing, areas of anomalous values ​​of various seismic parameters were revealed. A comprehensive interpretation of the data made it possible to determine the most probable location of the ore object (R) at pickets 3600-4800 m, where the following pertophysical features are observed: high acoustic rigidity above the object, strong absorption below the object, and a decrease in interval velocities in the area of ​​the object. This "image" corresponds to the previously obtained R-etalons in the areas of deep drilling in the area of ​​the Kola super-deep well.

Rice. 7 Differential processing of seismic data
when looking for hydrocarbon deposits. Western Siberia

Special computer processing makes it possible to obtain a series of parametric sections (maps of parameters). Each parametric map characterizes certain physical properties of the medium. The synthesis of parameters serves as the basis for the formation of the "image" of an oil (gas) object. The result of a comprehensive interpretation is a physical-geological model of the environment with a forecast for hydrocarbon deposits.

Rice. 8 Geoseismic model of the Pechenga structure
Kola Peninsula.

Rice. 9 Geoseismic model of the northwestern part of the Baltic Shield
Kola Peninsula.

Rice. 10 Quasi-density section along profile 031190 (37)
Western Siberia.

The oil-bearing sedimentary basins of Western Siberia should be attributed to a favorable type of section for the introduction of new technology. The figure shows an example of a quasi-density section constructed using the MDS programs on a R-5 PC. The resulting interpretation model is in good agreement with the drilling data. The lithotype marked in dark green at depths of 1900 m corresponds to mudstones of the Bazhenov Formation; The densest lithotypes of the section. Yellow and red varieties are quartz and mudstone sandstones, light green lithotypes correspond to siltstones. In the bottomhole part of the well, under the water-oil contact, a lens of quartz sandstones with high reservoir properties was opened.

PREDICTION OF THE GEOLOGICAL SECTION BASED ON MDS DATA

At the stage of prospecting and exploration, MDS is an integral part of the exploration process, both in structural mapping and at the stage of real forecasting.
On fig. 8 shows a fragment of the Geoseismic model of the Pechenga structure. The basis of the fuel and lubricants are the seismic data of the international experiments KOLA-SD and 1-EB in the area of ​​the Kola superdeep well SG-3 and the data of prospecting and exploration works.
The stereometric combination of the geological surface and deep structural (S) sections of the MDS on real geological scales allows one to get a correct idea of ​​the spatial structure of the Pechenga synclinorium. The main ore-bearing complexes are represented by terrigenous and tuffaceous rocks; their boundaries with surrounding mafic rocks are strong seismic boundaries, which provides reliable mapping of ore-bearing horizons in the deep part of the Pechenga structure.
The resulting seismic framework is used as a structural basis for the Physical Geological Model of the Pechenga ore region.
On fig. Figure 9 shows elements of the geoseismic model for the northwestern part of the Baltic Shield. Fragment of geotraverse 1-EV along the line SG-3 - Liinakha-mari. In addition to the traditional structural section (S), parametric sections were obtained:
A - quasi-stiffness section characterizes the contrast of various geological blocks. The Pechenga block and the Liinakhamari block are distinguished by high acoustic rigidity; the zone of the Pitkjarvin syncline is the least contrasting.
F - the section of quasi-absorption reflects the degree of consolidation of rock
breeds. The Liinakhamari block is characterized by the least absorption, and the largest is noted in the inner part of the Pechenga structure.
V, I are sections of average and interval velocities. The kinematic characteristics are noticeably heterogeneous in the upper part of the section and stabilize below the level of 4-5 km. The Pechenga block and the Liinakhamari block are characterized by increased velocities. In the northern part of the Pitkyayarvin syncline, in section I, a “trough-shaped” structure is observed with consistent values ​​of interval velocities Vi = 5000-5200 m/s, corresponding in terms of the distribution area of ​​Late Archean granitoids.
A comprehensive interpretation of the parametric sections of the MDS and materials of other geological and geophysical methods is the basis for creating a Physical and Geological model of the West Kola region of the Baltic Shield.

PREDICTION OF LITHOLOGY OF THE ENVIRONMENT

The identification of new parametric capabilities of the MDS is associated with the study of the relationship of various seismic parameters with the geological characteristics of the environment. One of the new (mastered) MDS parameters is the quasi-density. This parameter can be identified on the basis of studying the sign of the seismic signal reflection coefficient at the boundary of two lithophysical complexes. With insignificant changes in the velocities of seismic waves, the sign characteristic of the wave is determined mainly by the change in the density of rocks, which makes it possible to study the material composition of the medium in some types of sections using a new parameter.
The oil-bearing sedimentary basins of Western Siberia should be attributed to a favorable type of section for the introduction of new technology. Below in fig. Figure 10 shows an example of a quasi-density section constructed using the MDS programs on a R-5 PC. The resulting interpretation model is in good agreement with the drilling data. The lithotype marked in dark green at depths of 1900 m corresponds to mudstones of the Bazhenov Formation; the densest lithotypes of the section. Yellow and red varieties are quartz and mudstone sandstones, light green lithotypes correspond to siltstones. A lens of quartz sandstones was opened in the bottomhole part of the well under the water-oil contact
with high collection properties.

COMPLEXING THE DATA OF THE CDP AND THE SHP

When conducting regional and CDP prospecting and exploration work, it is not always possible to obtain data on the structure of the near-surface part of the section, which makes it difficult to link geological mapping materials to deep seismic data (Fig. 11). In such a situation, it is expedient to use refraction profiling in the OGP variant, or to process the available CDP materials using a special refraction-OGP technology. The bottom drawing shows an example of combining refraction and CDP data for one of the CDP seismic profiles worked out in Central Karelia. The obtained materials made it possible to link the deep structure with the geological map and clarify the location of the Early Proterozoic Paleodepressions, which are promising for ore deposits of various minerals.

common depth point, CDP) is a seismic survey method.

Seismic exploration - a method of geophysical exploration of the earth's interior - has many modifications. Here we will consider only one of them, the method of reflected waves, and, moreover, the processing of materials obtained by the method of multiple overlaps, or, as it is usually called, the method of common depth point (CDP or CDP).

Story

Born in the early 60s of the last century, it became the main method of seismic exploration for many decades. Rapidly developing both quantitatively and qualitatively, it has completely supplanted the simple method of reflected waves (ROW). On the one hand, this is due to the no less rapid development of computer (first analog and then digital) processing methods, and on the other hand, the possibility of increasing the productivity of field work by using large reception bases that are impossible in the SW method. Not the last role was played here by the rise in the cost of work, that is, the increase in the profitability of seismic exploration. To justify the increase in the cost of work, many books and articles were written on the perniciousness of multiple waves, which since then have become the basis for justifying the application of the common depth point method.

However, this transition from the oscilloscope MOB to the machine-based MOGT was not so cloudless. The SVM method was based on linking hodographs at mutual points. This linking reliably ensured the identification of hodographs belonging to the same reflecting boundary. The method did not require any corrections to ensure phase correlation - neither kinematic nor static (dynamic and static corrections). Changes in the shape of the correlated phase were directly related to changes in the properties of the reflecting horizon, and only with them. Neither inaccurate knowledge of the reflected wave velocities nor inaccurate static corrections affected the correlation.

Coordination at mutual points is impossible at large distances of receivers from the point of excitation, since the hodographs are intersected by trains of low-speed interference waves. Therefore, CDP processors abandoned the visual linking of mutual points, replacing them by obtaining a sufficiently stable signal shape for each result point by obtaining this shape by summing approximately homogeneous components. The exact quantitative correlation of times has been replaced by a qualitative estimate of the form of the resulting total phase.

The process of registering an explosion or any source of excitation other than a vibroseis is similar to taking a photograph. The flash illuminates the environment and the response of this environment is captured. However, the response to an explosion is much more complex than a photograph. The main difference is that a photograph captures the response of a single, albeit arbitrarily complex surface, while an explosion evokes the response of multiple surfaces, one under or inside another. Moreover, each overlying surface leaves its mark on the image of the underlying ones. This effect can be seen if you look at the side of a spoon immersed in tea. It seems broken, while we firmly know that there is no break. The surfaces themselves (the boundaries of the geological section) are never flat and horizontal, which is manifested in their responses - hodographs.

Treatment

The essence of CDP data processing is that each trace of the result is obtained by summing the original channels in such a way that the sum includes signals reflected from the same point of the deep horizon. Before summing, it was necessary to introduce corrections to the recording times in order to transform the recording of each individual trace, bring it to a form similar to the trace at the shot point, i.e., convert it to the form t0. This was the original idea of ​​the authors of the method. Of course, it is impossible to select the required channels for stacking without knowing the structure of the medium, and the authors set the condition for applying the method to the presence of a horizontally layered section with slope angles not exceeding 3 degrees. In this case, the coordinate of the reflecting point is quite exactly equal to half the sum of the coordinates of the receiver and source.

However, practice has shown that if this condition is violated, nothing terrible happens, the resulting cuts have a familiar look. The fact that in this case the theoretical justification of the method is violated, that reflections from one point, but from the site, are summed up, the greater, the greater the angle of inclination of the horizon, did not bother anyone, because the assessment of the quality and reliability of the section was no longer accurate, quantitative, but approximate quality. It turns out a continuous axis of in-phase, which means that everything is in order.

Since each trace of the result is the sum of a certain set of channels, and the quality of the result is assessed by the stability of the phase shape, it is sufficient to have a stable set of the strongest components of this sum, regardless of the nature of these components. So, summing up some low-speed interference, we get a quite decent cut, approximately horizontally layered, dynamically rich. Of course, it will have nothing to do with a real geological section, but it will fully meet the requirements for the result - the stability and length of the in-phase phases. In practical work, a certain amount of such interference always enters the sum, and, as a rule, the amplitude of these interferences is much greater than the amplitude of the reflected waves.

Let's return to the analogy of seismic exploration and photography. Imagine that on a dark street we meet a man with a lantern, with which he shines into our eyes. How can we consider it? Apparently, we will try to cover our eyes with our hands, shield them from the lantern, then it becomes possible to examine a person. Thus, we divide the total lighting into components, remove the unnecessary, focus on the necessary.

When processing CDP materials, we do exactly the opposite - we summarize, combine the necessary and the unnecessary, hoping that the necessary will come forward on its own. Moreover. From photography, we know that the smaller the image element (the graininess of the photographic material), the better, the more detailed the picture. You can often see in documentary television films, when you need to hide, distort the image, it is presented with large elements, behind which you can see some object, see its movements, but it is simply impossible to see such an object in detail. This is exactly what happens when the channels are summed during the processing of CDP materials.

In order to obtain in-phase addition of signals even with a perfectly flat and horizontal reflecting boundary, it is necessary to provide corrections that ideally compensate for the inhomogeneities of the relief and the upper part of the section. It is also ideally necessary to compensate for the curvature of the hodograph in order to move the reflection phases obtained at distances from the point of excitation by times corresponding to the time of passage of the seismic beam to the reflecting surface and back along the normal to the surface. Both are impossible without a detailed knowledge of the structure of the upper part of the section and the shape of the reflecting horizon, which is impossible to provide. Therefore, when processing, point, fragmentary information about the zone of low velocities and approximation of reflecting horizons by a horizontal plane are used. The consequences of this and methods for extracting maximum information from the richest material provided by the CDP are discussed in the description of "Dominant Processing (Baybekov's Method)".

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MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION

Federal Agency for Education

TOMSK POLYTECHNICAL UNIVERSITY

Institute of Natural Resources

course project

on the course "Seismic Exploration"

Methodology and technoCDP seismic survey

Completed: student gr. 2A280

Severvald A.V.

Checked:

Rezyapov G.I.

Tomsk -2012

• Introduction
• 1. Theoretical foundations of the common depth point method
• 1.1 Theory of the CDP method
• 1.2 Features of the CDP hodograph
• 1.3 CDP interference system
• 2. Calculation of the optimal observing system of the CDP method
• 2.1 Seismological model of the section and its parameters
• 2.2 Calculation of the observing system of the CDP method
• 2.3 Calculation of hodographs of useful waves and interference waves
• 2.4 Calculation of the delay function of the interference waves
• 2.5 Calculation of the parameters of the optimal observing system
• 3. Technology of field seismic surveys
• 3.1 Observation network requirements in seismic exploration
• 3.2 Conditions for the excitation of elastic waves
• 3.3 Conditions for receiving elastic waves
• 3.4 Selection of hardware and special equipment
• 3.5 Organization of field seismic surveys
• Conclusion
• Bibliography

Introduction

Seismic exploration is one of the leading methods for studying the structure, structure and composition of rocks. The main field of application is the search for oil and gas fields.

The purpose of this course work is to consolidate knowledge in the course "seismic exploration"

The objectives of this course work are:

1) consideration of the theoretical foundations of the CDP method;

2) compiling a seismogeological model, on the basis of which the parameters of the OGT-2D observation system are calculated;

3) consideration of the technology for conducting seismic surveys;

1. Theoretical foundations of the common depth point method

1.1 Theory of the CDP method

The method (method) of a common depth point (CDP) is a modification of the SWM based on a system of multiple overlaps and characterized by the summation (accumulation) of reflections from common areas of the boundary at different locations of sources and receivers. The CDP method is based on the assumption of the correlation of waves generated by sources distant at different distances, but reflected from a common section of the boundary. The inevitable differences in the spectra of different sources and the errors in the times during summation require a reduction in the spectra of useful signals. The main advantage of the CDP method is the possibility of amplifying singly reflected waves against the background of multiple and converted reflected waves by equalizing the times reflected from common deep points and summing them up. The specific features of the CDP method are determined by the properties of directionality during summation, data redundancy, and statistical effect. They are most successfully implemented in digital registration and processing of primary data.

Rice. 1.1 Schematic representation of an element of the observation system and a seismogram obtained by the CDP method. A and A"-- axes of common mode of the reflected single wave, respectively, before and after the introduction of the kinematic correction; V and V" is the in-phase axis of the multiple reflected wave, respectively, before and after the introduction of the kinematic correction.

Rice. 1.1 illustrates the CDP summation principle using a fivefold overlap system as an example. Sources of elastic waves and receivers are located on the profile symmetrically to the projection of the common deep point R of the horizontal boundary onto it. A seismogram composed of five records obtained at reception points 1, 3, 5, 7, 9 (the number of reception points starts from their own point of excitation) with excitation at points V, IV, III, II, I is shown above the CD line. It forms a CDP seismogram, and the hodographs of the reflected waves correlated on it are the hodographs of the CDP. On observation bases usually used in the CDP method, not exceeding 3 km, the CDP hodograph of a singly reflected wave is approximated by a hyperbola with sufficient accuracy. In this case, the minimum of the hyperbola is close to the projection onto the line of observation of the common depth point. This property of the CDP hodograph largely determines the relative simplicity and efficiency of data processing.

To convert a set of seismic records into a time section, kinematic corrections are introduced into each CDP seismogram, the values ​​of which are determined by the velocities of the media covering the reflecting boundaries, i.e. they are calculated for single reflections. As a result of the introduction of corrections, the axes of in-phase occurrences of single reflections are transformed into lines t 0 = const. In this case, the in-phase axes of regular interference waves (multiple, converted waves), the kinematics of which differs from the introduced kinematic corrections, are transformed into smooth curves. After the introduction of kinematic corrections, the traces of the corrected seismogram are simultaneously summarized. In this case, the singly reflected waves are added in phase and are thus emphasized, while regular interference, and among them, first of all, repeatedly reflected waves, added with phase shifts, are weakened. Knowing the kinematic features of the interference wave, it is possible to calculate in advance the parameters of the observation system using the CDP method (the length of the CDP hodograph, the number of channels on the CDP seismogram equal to the tracking multiplicity), which provide the required interference attenuation.

CDP gathers are generated by sampling channels from the gather from each shot (called Common Shot Gathers - CPI) in accordance with the requirements of the system element shown in Fig. 1., which shows: the first entry of the fifth point of excitation, the third entry of the fourth, etc. until the ninth entry of the first point of excitation.

This procedure of continuous sampling along the profile is possible only with multiple overlaps. It corresponds to the superimposition of time sections obtained independently of each point of excitation, and indicates the redundancy of information implemented in the CDP method. This redundancy is an important feature of the method and underlies the refinement (correction) of static and kinematic corrections.

The velocities required to refine the input kinematic corrections are determined from the CDP travel time curves. To do this, CDP seismograms with approximately calculated kinematic corrections are subjected to multi-temporal summation with additional non-linear operations. In addition to determining the effective velocities of singly reflected waves, the kinematic features of interference waves are found from the CDP summaries to calculate the parameters of the receiving system. CDP observations are carried out along longitudinal profiles.

To excite waves, explosive and impact sources are used, which require observations with a large (24–48) overlap ratio.

The processing of CDP data on a computer is divided into a number of stages, each of which ends with the output of the results for the interpreter to make a decision: 1) pre-processing; 2) determination of optimal parameters and construction of the final time section; 3) determination of the velocity model of the medium; 4) construction of a deep section.

Multiple overlap systems currently form the basis of field observations (data collection) in SEM and determine the development of the method. CDP stacking is one of the main and efficient processing procedures that can be implemented on the basis of these systems. The CDP method is the main modification of the method for prospecting and exploration of oil and gas fields in almost all seismogeological conditions. However, the CDP stacking results have some limitations. These include: a) a significant reduction in the frequency of registration; b) the weakening of the locality property of the SWT due to the increase in the volume of the inhomogeneous space at large distances from the source, which are characteristic of the CDP method and necessary to suppress multiple waves; c) the imposition of single reflections from close boundaries due to their inherent convergence of the in-phase axes at large distances from the source; d) sensitivity to side waves that interfere with the tracking of target sub-horizontal boundaries due to the location of the main maximum of the spatial stacking directivity characteristic in a plane perpendicular to the stacking base (profile).

These limitations generally lead to a downward trend in the resolution of the MOB. Given the prevalence of the CDP method, they should be taken into account in specific seismogeological conditions.

1.2 Features of the CDP hodograph

Rice. 1.2 Scheme of the CDP method for the inclined occurrence of the reflecting boundary.

1. CDP hodograph of a singly reflected wave for a homogeneous covering medium is a hyperbola with a minimum at the point of symmetry (CDP point);

2. with an increase in the angle of inclination of the interface, the steepness of the CDP hodograph and, accordingly, the time increment decrease;

3. the shape of the CDP hodograph does not depend on the sign of the inclination angle of the interface (this feature follows from the principle of reciprocity and is one of the main properties of the symmetrical explosion-device system;

4. for a given t 0 the CDP hodograph is a function of only one parameter - v CDP, which is called the fictitious speed.

These features mean that in order to approximate the observed CDP hodograph by a hyperbola, it is necessary to choose a value v CDP that satisfies the given t 0 and is determined by the formula (v CDP =v/cosц). This important consequence makes it easy to implement the search for the in-phase axis of the reflected wave by analyzing the CDP seismogram along a fan of hyperbolas having a common value t 0 and different v CDPs.

1.3 CDP interference system

In interference systems, the filtering procedure consists in summing seismic traces along given lines φ(x) with weights that are constant for each trace. Usually, the summation lines correspond to the shape of useful wave hodographs. The weighted summation of fluctuations of different traces y n (t) is a special case of multichannel filtering, when the operators of individual filters h n (t) are d-functions with amplitudes equal to the weight coefficients d n:

(1.1)

where f m - n is the difference between the times of summation of oscillations on track m, which refers to the result, and on track n.

Let us give relation (1.1) a simpler form, taking into account that the result does not depend on the position of the point m and is determined by the time shifts of the traces φ n relative to an arbitrary origin. Let us obtain a simple formula describing the general algorithm of interference systems,

(1.2)

Their varieties differ in the nature of the change in the weight coefficients d n and time shifts f n: both can be constant or variable in space, and the latter, in addition, can change in time.

Let an ideally regular wave g(t,x) with arrival hodograph t(x)=t n be recorded on seismic traces:

hodograph seismological interference wave

Substituting this into (1.2), we obtain an expression describing the oscillations at the output of the interference system,

where and n \u003d t n - f n.

The values ​​and n determine the deviation of the wave hodograph from the given summation line. Find the spectrum of filtered oscillations:

If the hodograph of a regular wave coincides with the summation line (and n ? 0), then in-phase addition of oscillations occurs. For this case, denoted by u=0, we have

Interference systems are built to amplify in-phase summed waves. To achieve this result, it is necessary that H 0 (SCH) was the maximum value of the modulus of the function H and(SCH).Most often, single interference systems are used, which have equal weights for all channels, which can be considered single: d n ?1. In this case

In conclusion, we note that the summation of non-plane waves can be carried out using seismic sources by introducing appropriate delays at the moments of oscillation excitation. In practice, these types of interference systems are implemented in a laboratory version, introducing the necessary shifts in the records of vibrations from individual sources. Shifts can be selected in such a way that the incident wave front has an optimal shape from the point of view of increasing the intensity of waves reflected or diffracted from local sections of the seismogeological section of particular interest. This technique is known as incident wave focusing.

2. Calculation of the optimal observing system of the CDP method

2.1 Seismological model of the section and its parameters

The seismic geological model has the following parameters:

We calculate the reflection coefficients and the coefficients of double passage according to the formulas:

We get:

We set possible options for the passage of waves along this section:

Based on these calculations, we build a theoretical vertical seismic profile (Fig. 2.1), which reflects the main types of waves that occur in specific seismogeological conditions.

Rice. 2.1. Theoretical vertical seismic profile (1 - useful wave, 2.3 - multiple waves - interference, 4.5 - multiple waves that are not interference).

For the target fourth boundary, we use wave number 1 - a useful wave. Waves with an arrival time of -0.01-+0.05 of the time of the "target" wave are interference interference waves. In this case, waves number 2 and 3. All other waves will not be interference.

Let's calculate the double run time and the average velocity along the section for each layer using formula (3.4) and build a velocity model.

We get:

Rice. 2.2. speed model

2.2 Calculation of the observing system of the CDP method

The amplitudes of useful reflected waves from the target boundary are calculated by the formula:

(2.5)

where A p is the reflection coefficient of the target boundary.

The amplitudes of multiple waves are calculated by the formula:

.(2.6)

In the absence of data on the absorption coefficient, we accept =1.

We calculate the amplitudes of multiple and useful waves:

The multiple wave 2 has the highest amplitude. The obtained values ​​of the amplitude of the target wave and noise make it possible to calculate the required degree of suppression of the multiple wave.

Insofar as

2.3 Calculation of hodographs of useful waves and interference waves

The calculation of the travel time curves of multiple waves is carried out under simplifying assumptions about a horizontally layered model of the medium and flat boundaries. In this case, multiple reflections from several interfaces can be replaced by a single reflection from some fictitious interface.

The average velocity of the fictitious medium is calculated over the entire vertical path of the multiple wave:

(2.7)

The time is determined by the pattern of formation of a multiple wave on the theoretical VSP or by summing the travel times in all layers.

(2.8)

We get the following values:

The multiple wave hodograph is calculated by the formula:

(2.9)

The useful wave hodograph is calculated by the formula:

(2.10)

Figure 2.3 Hodographs of useful wave and interference wave

2.4 Calculation of the delay function of the interference waves

We introduce kinematic corrections calculated by the formula:

?tk(x, to) = t(x) - to(2.11)

The multiple wave delay function (x) is determined by the formula:

(x) \u003d t cr (хi) - t env (2.12)

where t kr(хi) is the time corrected for the kinematics and t okr is the time at zero distance of the receiving point from the excitation point.

Fig 2.4 Multiple delay function

2.5 Calculation of the parameters of the optimal observing system

An optimal observing system should provide the greatest result at low material costs. The required degree of interference suppression is D=5, the lower and upper frequencies of the interference wave spectrum are 20 and 60 Hz, respectively.

Rice. 2.5 CDP summation directional characteristic for N = 24.

According to the set of directivity characteristics, the minimum number of multiplicity is N=24.

(2.13)

Knowing P, we remove y min \u003d 4 and y max \u003d 24.5

Knowing the minimum and maximum frequency, 20 and 60 Hz, respectively, we calculate f max .

f min *f max =4f max =0.2

f max * f max \u003d 24.5 f max \u003d 0.408

The value of the delay function f max =0.2, which corresponds to x max =3400 (see Fig. 2.4). After the removal of the first channel from the excitation point, x m in =300, deflection arrow D=0.05, D/f max =0.25, which satisfies the condition. This indicates the satisfaction of the selected directivity characteristic, the parameters of which are the values ​​N=24, f max =0.2, x m in =300 m and the maximum distance x max =3400 m.

Theoretical hodograph length H*= x max - x min =3100m.

The practical length of the hodograph is H = K*?x, where K is the number of channels of the recording seismic station and?x is the step between the channels.

Let's take a seismic station with 24 channels (K=24=N*24), ?х=50.

Let's recalculate the observation interval:

Calculate the excitation interval:

As a result, we get:

The observation system on a deployed profile is shown in Fig. 2.6

3. Technology of field seismic surveys

3.1 Observation network requirements in seismic exploration

Observing systems

Currently, the system of multiple overlaps (SMP) is mainly used, which provides summation over a common depth point (CDP), and thereby a sharp increase in the signal-to-noise ratio. The use of non-longitudinal profiles reduces the cost of field work and dramatically increases the manufacturability of field work.

At present, only complete correlation observation systems are practically used, which make it possible to carry out a continuous correlation of useful waves.

Seismic sounding is used during reconnaissance survey and at the stage of experimental work for the purpose of preliminary study of the wave field in the study area. In this case, the observing system should provide information on the depths and angles of inclination of the studied reflectors, as well as the determination of effective velocities. There are linear, which are short segments of longitudinal profiles, and areal (cross, radial, circular) seismic sounding, when observations are made on several (from two or more) intersecting longitudinal or non-longitudinal profiles.

Of the linear seismic soundings, common depth point (CDP) soundings, which are elements of a multiple profiling system, have received the greatest use. The mutual location of the excitation points and observation sites is chosen in such a way that reflections from the same section of the boundary under study are recorded. The resulting seismograms are mounted.

The multiple profiling (overlapping) systems are based on the common depth point method, which uses central systems, systems with a variable shot point within the receiving base, flank one-sided systems without and with the removal of the shot point, as well as flank double-sided (counter) systems without take-out and with the removal of the explosion point.

The most convenient for production work and provide maximum system performance, in the implementation of which the observation base and the excitation point are displaced after each explosion in one direction by equal distances.

To trace and determine the elements of the spatial occurrence of steeply dipping boundaries, as well as tracing tectonic faults, it is advisable to use conjugated profiles. which are almost parallel, and the distance between them is chosen to ensure continuous wave correlation, they are 100-1000 m.

When observing on one profile, the PV is placed on another, and vice versa. Such an observation system ensures continuous wave correlation along conjugated profiles.

Multiple profiling on several (from 3 to 9) conjugated profiles is the basis of the wide profile method. In this case, the observation point is located on the central profile, and excitations are performed sequentially from points located on parallel conjugated profiles. The multiplicity of tracking the reflecting boundaries along each of the parallel profiles can be different. The total multiplicity of observations is determined by the product of the multiplicity for each of the conjugated profiles by their total number. The increase in the cost of observing such complex systems is justified by the possibility of obtaining information about the spatial features of the reflecting boundaries.

Areal observing systems built on the basis of a cross array provide an areal sampling of traces along the CDP due to successive overlapping of cruciform arrays, sources and receivers. As a result of such processing, a field of 576 midpoints is formed. If we sequentially shift the arrangement of seismic receivers and the excitation line crossing it along the x axis by a step dx and repeat the registration, then a 12-fold overlap will be achieved as a result, the width of which is equal to half the excitation and reception base along the y axis by a step dy, an additional 12-fold overlap is achieved. , and the total overlap will be 144.

In practice, more economical and technological systems are used, for example, 16-fold. For its implementation, 240 recording channels and 32 excitation points are used. The fixed distribution of sources and receivers shown in Fig. 6 is called a block. After receiving oscillations from all 32 sources, the block is shifted by a step dx, the reception from all 32 sources is repeated, etc. Thus, the entire strip along the x-axis is worked out from the beginning to the end of the study area. The next strip of five reception lines is placed parallel to the previous one so that the distance between adjacent (nearest) reception lines of the first and second strips is equal to the distance between the reception lines in the block. In this case, the source lines of the first and second bands overlap by half the excitation base, and so on. Thus, in this version of the system, the receiving lines are not duplicated, and signals are excited twice at each source point.

Profiling networks

For each exploration area, there is a limit on the number of observations, below which it is impossible to build structural maps and diagrams, as well as an upper limit, above which the accuracy of construction does not increase. The choice of a rational observation network is influenced by the following factors: the shape of the boundaries, the range of variation in depths, measurement errors at observation points, sections of seismic maps, and others. Exact mathematical dependencies have not yet been found, and therefore approximate expressions are used.

There are three stages of seismic exploration: regional, prospecting and detailed. At the stage of regional work, the profiles tend to be directed to the cross of the strike of structures after 10–20 km. This rule is deviated from when conducting connecting profiles and linking with wells.

During search operations, the distance between adjacent profiles should not exceed half of the estimated length of the major axis of the structure under study, usually it is no more than 4 km. In detailed studies, the density of the network of profiles in different parts of the structure is different and usually does not exceed 4 km. In detailed studies, the density of the network of profiles in different parts of the profiles is different and usually does not exceed 2 km. The network of profiles is concentrated in the most interesting places of the structure (crown, fault lines, wedging zones, etc.). The maximum distance between the connecting profiles does not exceed twice the distance between the exploration profiles. In the presence of discontinuous disturbances in the study area in each of the large blocks, the network of profiles for creating closed polygons is complicated. If the block sizes are small, then only connecting profiles are carried out, Salt domes are explored along a radial network of profiles with their intersection above the dome arch, connecting profiles pass along the periphery of the dome, connecting profiles pass along the periphery of the dome.

When conducting seismic surveys in the area where seismic surveys were previously performed, the network of new profiles should partially repeat the old profiles to compare the quality of the old and new materials. reception should be located near the wells.

Profiles should be as straight as possible, taking into account the minimum agricultural damage. When working on a CDP, the profile break angle should be limited, since the angle of inclination and the direction of the dip of the boundaries can only be estimated before the start of field work, and accounting for and correlating these values ​​in the summation process presents significant difficulties. If we take into account only the distortion of the wave kinematics, then the admissible kink angle can be estimated from the relation

b=2arcsin(vср?t0/xmaxtgf),

where?t=2?H/vav - time increment along the normal to the boundary; xmax - maximum length of the hodograph; f is the angle of incidence of the boundary. The dependence of the value of b as a function of the generalized argument vсрt0/tgf for various xmax (from 0.5 to 5 km) is shown in (Fig. 4), which can be used as a palette for estimating the permissible values ​​of the profile break angle under specific assumptions about the structure of the medium. Given the admissible value of the dephasing of the pulse terms (for example, ¼ of the period T), we can calculate the value of the argument for the maximum possible angle of incidence of the boundary and the minimum possible average velocity of wave propagation. The ordinate of the line with xmax at this value of the argument will indicate the value of the maximum allowable corner angle of the profile.

To establish the exact location of the profiles, even during the design of the work, the first reconnaissance is carried out. Detailed reconnaissance is carried out during field work.

3.2 Conditions for the excitation of elastic waves

Oscillations are excited by means of explosions (explosive charges or LH lines) or non-explosive sources.

Methods for excitation of oscillations are selected in accordance with the conditions, tasks and methods of field work.

The optimal excitation option is selected based on the practice of previous work and is refined by studying the wave field in the process of experimental work.

Excitation by explosive sources

Explosions are made in wells, pits, in cracks, on the surface of the earth, in the air. Only electrical blasting is used.

During explosions in wells, the greatest seismic effect is achieved when the charge is immersed below the zone of low velocities, during an explosion in plastic and watered rocks, when the charges in wells are capped with water, drilling mud or soil.

The choice of the optimal depths of the explosion is carried out according to the observations of the MSC and the results of experimental work

In the process of field observations on the profile, one should strive to maintain the constancy (optimality) of the excitation conditions.

In order to obtain a permitted record, the mass of a single charge is chosen to be minimal, but sufficient (taking into account the possible grouping of explosions) to ensure the necessary depth of research. Grouping of explosions should be used when the effectiveness of single charges is insufficient. The correctness of the choice of mass of charges is periodically monitored.

The explosive charge must descend to a depth that differs from the specified one by no more than 1 m.

Preparation, immersion and detonation of the charge are carried out after the relevant orders of the operator. The blaster must immediately inform the operator of a failure or incomplete explosion.

Upon completion of blasting, the wells, pits and pits remaining after the explosion must be liquidated in accordance with the "Instruction for the elimination of the consequences of an explosion during seismic surveys"

When working with detonating cord lines (LDC), it is advisable to place the source along the profile. The parameters of such a source - the length and number of lines - are chosen based on the conditions for ensuring sufficient intensity of the target waves and acceptable distortions in the shape of their records (the length of the source should not exceed half the minimum apparent wavelength of the useful signal). In a number of problems, the LDSH parameters are chosen in order to provide the desired source directivity.

To attenuate the sound wave, it is recommended to deepen the lines of the detonating cord; in winter - sprinkle with snow.

When carrying out blasting operations, the requirements stipulated by the "Uniform Safety Rules for Explosive Operations" must be observed.

To excite oscillations in reservoirs, only non-explosive sources are used (gas detonation installations, pneumatic sources, etc.).

With non-explosive excitation, linear or areal groups of synchronously operating sources are used. The parameters of the groups - the number of sources, the base, the step of movement, the number of impacts (at a point) - depend on the surface conditions, the wave field of interference, the required depth of research and are selected in the process of experimental work

When carrying out work with non-explosive sources, it is necessary to observe the identity of the main parameters of the mode of each of the sources operating in a group.

The synchronization accuracy must correspond to the sampling step during registration, but be no worse than 0.002 s.

Excitation of oscillations by impulse sources is carried out, if possible, on dense compacted soils with a preliminary compaction blow.

The depth of the "stamp" from the blows of the plate during the working excitation of the sources should not exceed 20 cm.

When working with non-explosive sources, the safety regulations and work procedures provided for by the relevant instructions for safe work with non-explosive sources and technical operating instructions must be strictly observed.

The excitation of transverse waves is carried out using horizontally or obliquely directed shock-mechanical, explosive or vibrational effects

To implement the selection of waves by polarization in the source, at each point, actions are performed that differ in direction by 180 o.

The mark of the moment of explosion or impact, as well as the vertical time, must be clear and stable, ensuring the determination of the moment with an error of no more than a sampling step.

If work is carried out at one object with different sources of excitation (explosions, vibrators, etc.), duplication of physical observations should be ensured with the receipt of records from each of them at the places of change of sources.

Excitation by pulsed sources

Numerous experience of work with surface pulsed emitters shows that the required seismic effect and acceptable signal-to-noise ratios are achieved with the accumulation of 16-32 impacts. This number of accumulations is equivalent to explosions of TNT charges weighing only 150–300 g. The high seismic efficiency of emitters is explained by the high efficiency of weak sources, which makes their use in seismic exploration promising, especially in the CDP method, when N-fold summation occurs at the processing stage, providing additional increase in the signal-to-noise ratio.

Under the action of multiple impulse loads with the optimal number of impacts at one point, the elastic properties of the soil are stabilized and the amplitudes of the excited oscillations remain practically unchanged. However, with further application of loads, the soil structure is destroyed and the amplitudes decrease. The greater the pressure on the ground d, the greater the number of impacts Nk, the amplitude of the oscillations reaches a maximum and the smaller the flat section of the curve A=?(n). The number of impacts Nk, at which the amplitude of the excited oscillations begins to decrease, depends on the structure, material composition and moisture content of the rocks and for most real soils does not exceed 5-8. With impulse loads developed by gas-dynamic sources, the difference in the amplitudes of oscillations excited by the first (A1) and second (A2) shocks is especially large, the ratio of which A2 / A1 can reach values ​​of 1.4-1.6. Differences between A2 and A3, A3 and A4, etc. significantly less. Therefore, when using ground sources, the first impact at a given point is not summed up with the others and serves only for preliminary soil compaction.

Before production work using non-explosive sources on each new area, a cycle of work is carried out to select the optimal conditions for excitation and registration of seismic wave fields.

3.3 Conditions for receiving elastic waves

With pulsed excitation, one always strives to create in the source a sharp and short pulse, sufficient for the formation of intense waves reflected from the studied horizons. We do not have strong means of influencing the shape and duration of these pulses in explosive and impact sources. We also do not have highly effective means of influencing the reflective, refractive and absorbing properties of rocks. However, seismic exploration has a whole arsenal of methodological techniques and technical means that allow, in the process of excitation and especially registration of elastic waves, as well as in the process of processing the received records, to most clearly highlight useful waves and suppress interference waves that interfere with their selection. For this purpose, differences are used in the direction of arrival of waves of different types to the earth's surface, in the direction of displacement of particles of the medium behind the fronts of incoming waves, in the frequency spectra of elastic waves, in the shapes of their hodographs, etc.

Elastic waves are recorded by a set of rather complex equipment mounted in special bodies mounted on highly passable vehicles - seismic stations.

A set of instruments that record soil vibrations caused by the arrival of elastic waves at one or another point on the earth's surface is called a seismic recording (seismic) channel. Depending on the number of points on the earth's surface, in which the arrival of elastic waves is simultaneously recorded, 24-, 48-channel and more seismic stations are distinguished.

The initial link of the seismic recording channel is a seismic receiver that perceives soil vibrations caused by the arrival of elastic waves and converts them into electrical voltages. Since the ground vibrations are very small, the electrical voltages that occur at the geophone output are amplified before registration. With the help of pairs of wires, the voltage from the output of the geophones is fed to the input of amplifiers mounted in the seismic station. To connect seismic receivers to amplifiers, a special stranded seismic cable is used, which is usually called a seismic streamer.

A seismic amplifier is an electronic circuit that amplifies the voltages applied to its input by tens of thousands of times. It can, with the help of special circuits of semi-automatic or automatic gain or amplitude controllers (PRU, PRA, AGC, ARA), amplify signals. Amplifiers include special circuits (filters) that allow the necessary frequency components of the signals to be amplified as much as possible, while others are minimally, i.e., to carry out their frequency filtering.

The voltage from the output of the amplifier is fed to the recorder. There are several ways to register seismic waves. Previously, the optical method of recording waves on photographic paper was most widely used. At present, elastic waves are recorded on a magnetic film. In either method, before recording begins, photographic paper or magnetic film is set in motion by means of tape drives. With the optical method of registration, the voltage from the output of the amplifier is applied to the mirror galvanometer, and with the magnetic method - to the magnetic head. When continuous recording is made on photographic paper or on magnetic film, the wave process recording method is called analog. Currently, the most widely used is the discrete (intermittent) recording method, which is usually called digital. In this method, the instantaneous values ​​of the voltage amplitudes at the output of the amplifier are recorded in a binary digital code, at regular intervals? t changing from 0.001 to 0.004 s. Such an operation is called time quantization, and the value ?t adopted in this case is called the quantization step. Discrete digital registration in binary code makes it possible to use universal computers for processing seismic data. Analog records can be processed on a computer after they have been converted into a discrete digital form.

The recording of ground vibrations at one point on the earth's surface is commonly referred to as a seismic trace or track. The set of seismic traces obtained at a number of adjacent points on the earth's surface (or wells) on photographic paper, in a visual analog form, constitutes a seismogram, and on a magnetic film, a magnetogram. In the process of recording, seismograms and magnetograms are marked with time stamps every 0.01 s, and the moment of excitation of elastic waves is noted.

Any seismic recording equipment introduces some distortion into the recorded oscillatory process. To isolate and identify waves of the same type on neighboring paths, it is necessary that the distortions introduced into them on all paths be the same. To do this, all elements of the recording channels must be identical to each other, and the distortions they introduce into the oscillatory process must be minimal.

Magnetic seismic stations are equipped with equipment that makes it possible to reproduce the record in a form suitable for its visual examination. This is necessary for visual control over the quality of the recording. Reproduction of magnetograms is carried out on a photo, plain or electrostatic paper using an oscilloscope, pen or matrix recorder.

In addition to the described nodes, seismic stations are supplied with power supplies, wired or radio communication with excitation points, and various control panels. Digital stations have analog-to-code and code-to-analog converters for converting analog recording into digital and vice versa, and circuits (logic) that control their operation. To work with vibrators, the station has a correlator. The bodies of digital stations are made dustproof and equipped with air conditioning equipment, which is especially important for the high-quality operation of magnetic stations.

3.4 Selection of hardware and special equipment

The analysis of the data processing algorithms of the CDP method determines the basic requirements for the equipment. Processing involving the selection of channels (the formation of CDP seismograms), AGC, the introduction of static and kinematic corrections, can be performed on specialized analog machines. When processing, including the operations of determining the optimal static and kinematic corrections, normalization of the record (linear AGC), various filtering modifications with the calculation of filter parameters from the original record, the construction of a velocity model of the medium and the transformation of a time section into a depth one, the equipment must have wide capabilities that provide systematic reconfiguration algorithms. The complexity of these algorithms and, most importantly, their continuous modification depending on the seismogeological characteristics of the object under study determined the choice of universal electronic computers as the most effective tool for processing CDP data.

Data processing of the CDP method on a computer allows you to quickly implement a full range of algorithms that optimize the process of extracting useful waves and their transformation into a section. The wide capabilities of computers have largely determined the use of digital recording of seismic data directly in the process of field work.

At the same time, at present, a significant part of seismic information is recorded by analog seismic stations. The complexity of the seismogeological conditions and the nature of the recording associated with them, as well as the type of equipment used to record data in the field, determine the processing process and the type of processing equipment. In the case of analog recording, processing can be performed on analog and digital machines, in digital recording, on digital machines.

The digital processing system includes a mainframe computer and a number of specialized external devices. The latter are intended for input-output of seismic information, performing individual continuously recurring computational operations (convolution, Fourier integral) at a speed significantly higher than the speed of the main computer, specialized graph plotters and viewing devices. In some cases, the entire processing process is implemented by two systems using a middle-class computer (preprocessor) and a high-class computer (main processor) as the main computers. The system, based on a medium-class computer, is used to enter field information, convert formats, record and place it in a standard form on a magnetic tape drive (NML) of a computer, reproduce all information in order to control field recording and input quality, and a number of standard algorithmic operations, mandatory for processing in any seismogeological conditions. As a result of data processing at the output of the preprocessor in binary code in the format of the main processor, the original seismic vibrations can be recorded in the sequence of channels of the CSP seismogram and the CDP seismogram, seismic vibrations corrected for the value of a priori static and kinematic corrections. Playback of the transformed record, in addition to analyzing the input results, allows you to select the post-processing algorithms implemented on the main processor, as well as determine some processing parameters (filter bandwidth, AGC mode, etc.). The main processor, in the presence of a preprocessor, is designed to perform the main algorithmic operations (determining the corrected static and kinematic corrections, calculating effective and reservoir velocities, filtering in various modifications, converting a time section into a depth section). Therefore, computers with high speed (10 6 operations per 1 s), operational (32-64 thousand words) and intermediate (disks with a capacity of 10 7 - 10 8 words) memory are used as the main processor. The use of a preprocessor makes it possible to increase the profitability of processing by performing a number of standard operations on a computer, the cost of operating which is significantly lower.

When processing analog seismic information on a computer, the processing system is equipped with specialized input equipment, the main element of which is a unit for converting continuous recording into a binary code. Further processing of the digital record obtained in this way is completely equivalent to the processing of digital registration data in the field. The use of digital stations for registration, the recording format of which coincides with the format of the NML computer, eliminates the need for a specialized input device. In fact, the data entry process is reduced to installing a field tape on an NML computer. Otherwise, the computer is equipped with a buffer tape recorder with a format equivalent to that of a digital seismic station.

Specialized devices for digital processing complex.

Before proceeding to a direct description of external devices, we will consider the issues of placing seismic information on a computer lepte (tape recorder of a digital station). In the process of converting a continuous signal, the amplitudes of reference values ​​taken at a constant interval dt are assigned a binary code that determines its numerical value and sign. Obviously, the number of reference values ​​c on a given t trace with a useful record duration t is equal to c = t/dt+1, and the total number c" of reference values ​​on an m-channel seismogram is c" = cm. In particular, at t = 5 s, dt = 0.002 s and m = 2, s = 2501, and s" = 60024 numbers written in binary code.

In the practice of digital processing, each numerical value that is the equivalent of a given amplitude is usually called a seismic word. The number of binary digits of a seismic word, called its length, is determined by the number of digits of the analog-to-code converter of a digital seismic station (an input device for encoding analog magnetic recording). A fixed number of binary digits that a digital machine operates when performing arithmetic operations is usually called a machine word. The length of the machine word is determined by the design of the computer and may be the same as the length of the seismic word or exceed it. In the latter case, when seismic information is entered into a computer, several seismic words are entered into each memory cell with a capacity of one machine word. This operation is called packing. The procedure for placing information (seismic words) on the magnetic tape of a computer storage device or the magnetic tape of a digital station is determined by their design and the requirements of processing algorithms.

Directly the process of recording digital information on a computer tape recorder is preceded by the stage of marking it into zones. Under the zone is understood a certain section of the tape, designed for the subsequent recording of k words, where k \u003d 2, and the degree n \u003d 0, 1, 2, 3. . ., and 2 should not exceed the capacity of RAM. When marking on the tracks of a magnetic tape, a code is written indicating the zone number, and a sequence of clock pulses separates each word.

In the process of recording useful information, each seismic word (binary code of the reference value) is recorded on a section of the magnetic tape separated by a series of clock pulses within the given zone. Depending on the design of tape recorders, parallel code, parallel-serial and serial code recording is used. With a parallel code, a number that is equivalent to a given reference amplitude is written in a line across the magnetic tape. For this, a multitrack block of magnetic heads is used, the number of which is equal to the number of bits in a word. Writing in a parallel-serial code provides for the placement of all information about a given word within several lines, arranged sequentially one after another. Finally, with a sequential code, information about a given word is recorded by one magnetic head along the magnetic tape.

The number of machine words K 0 within the zone of a computer tape recorder intended for placing seismic information is determined by the useful recording time t on a given trace, the quantization step dt, and the number of seismic words r packed into one machine word.

Thus, the first stage of computer processing of seismic information recorded by a digital station in the multiplex form provides for its demultiplexing, i.e., sampling of reference values ​​corresponding to their sequential placement on a given seismogram trace along the t axis and recording them in the NML zone, whose number programmatically assigned to this channel. The input of analog seismic information into a computer, depending on the design of a specialized input device, can be performed both by channel and in multiplex mode. In the latter case, the machine, according to a given program, performs demultiplexing and recording information in a sequence of reference values ​​on a given trace in the corresponding NML zone.

A device for inputting analog information into a computer.

The main element of the device for inputting analog seismic records into a computer is an analog-to-digital converter (ADC), which performs the operations of converting a continuous signal into a digital code. Several ADC systems are currently known. To encode seismic signals, in most cases bitwise feedback weighting converters are used. The principle of operation of such a converter is based on comparing the input voltage (reference amplitude) with the compensating one. The compensation voltage Uk changes bit by bit according to whether the sum of the voltages exceeds the input value U x . One of the main components of the ADC is a digital-to-analog converter (DAC), controlled by a program-specific null-organ that compares the converted voltage with the output voltage of the DAC. At the first clock pulse, a voltage U K equal to 1/2Ue appears at the DAC output. If it exceeds the total voltage U x , then the high-order trigger will be in the "zero" position. Otherwise (U x >U Kl), the high-order trigger will be in position one. Let the inequality U x< 1/2Uэ и в первом разряде выходного регистра записан нуль. Тогда во втором такте U x сравнивается с эталонным напряжением 1/4Uэ, соответствующим единице следующего разряда. Если U x >Ue, then a unit will be written in the second digit of the output register, and in the third cycle of comparison U x will be compared with the reference voltage 1/4Ue + 1/8Ue, corresponding to one in the next digit. In each next i-th cycle of comparison, if a unit was written in the previous one, the voltage Uki-1 increases by Ue /2 until U x is less than Uki. In this case, the output voltage U x is compared with Uki+1 = Ue / 2 Ue / 2, etc. As a result of comparing U x with a bit-changing UK, the triggers of those bits, the inclusion of which caused overcompensation, will be in the "zero" position, and position "one" - triggers of the discharges that provided the best approximation to the measured voltage. In this case, a number equivalent to the input voltage will be written in the output register,

Ux = ?aiUe/2

From the output register, through the interface unit of the input device, at the command of the computer, the digital code is sent to the computer for further software processing. Knowing the principle of operation of an analog-to-digital converter, it is not difficult to understand the purpose and principle of operation of the main blocks of the device for inputting analog information into a computer.

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The method of refracted waves. General overview of data processing methods. Principles of constructing a refractive boundary. Entering the parameters of the observation system. Correlation of waves and construction of hodographs. Consolidated hodographs of head waves. Determination of the limiting speed.

GENERAL DEEP POINT METHOD, CDP (a. common point depth method; n. reflexionsseismisches Verfahren des gemeinsamen Tiefpunkts; f. point de reflexion commun; i. metodo de punto commun profundo), is the main method of seismic exploration based on multiple registration and subsequent accumulation seismic wave signals reflected at different angles from the same local area (point) of the seismic boundary in the earth's crust. The CDP method was first proposed by the American geophysicist G. Maine in 1950 (patent published in 1956) to attenuate multiple reflected interference waves; it has been used since the late 60s.

When conducting research using the CDP method, the points of reception and excitation of seismic waves are located symmetrically with respect to each given point of the profile. At the same time, for simple models of the geological environment (for example, a layered-homogeneous medium with horizontal boundaries), within the framework of geometric seismic concepts, it can be assumed that the reflection of seismic waves at each boundary occurs at the same point (a common deep point). With inclined boundaries and other complications of the geological structure, wave reflections occur within the area, the dimensions of which are small enough to consider that the principle of locality is observed when solving a wide range of practical problems. Seismic waves are excited by explosions of explosives in, a detonating cord, or a group of non-explosives on the surface. To receive signals, linear (with the number of elements 10 or more), and in difficult surface conditions also area groups of seismic receivers are used. Observations are carried out, as a rule, along longitudinal profiles (less often curvilinear) using multichannel (48 channels or more) digital seismic stations. The overlap ratio is mainly 12-24, in difficult geological conditions and during detailed work 48 or more. The distance between the signal receiving points (observation step) is 40-80 m, with a detailed study of local complex heterogeneities up to 20-25 m, with regional studies up to 100-150 m. The distance between the excitation points is usually chosen as a multiple of the distance between the receiving points. Relatively large observation bases are used, the size of which is commensurate with or approximately equal to 0.5 of the depth of the target object and does not generally exceed 3-4 km. When studying complex environments, especially when working in water areas, various variants of 3D seismic survey systems using the CDP method are used, in which the CDP points are relatively evenly and with high density (25x25 m - 50x50 m) located on the study area or its individual linear sections. Registration of waves is carried out mainly in the frequency ranges 8-15 - 100-125 Hz. Processing is carried out on high-performance geophysical computing systems that allow for preliminary (before CDP stacking) attenuation of interference waves; increase the resolution of records; restore the true ratios of the amplitudes of the reflected waves associated with the variability of the reflecting properties of the boundaries; summarize (accumulate) the signals reflected from the CDP; build temporary dynamic sections and their various transformations (sections depicting instantaneous frequencies, phases, amplitudes, etc. ); study in detail the distribution of velocities and build a deep dynamic section, which serves as the basis for geological interpretation.

The CDP method is used in the search and exploration of oil and gas fields in various seismogeological conditions. Its application almost everywhere has increased the depth of research, the accuracy of mapping seismic boundaries and the quality of preparing structures for deep drilling, has made it possible in a number of oil and gas provinces to move on to preparing for non-anticline traps, to solve problems of local forecasting of the material composition of deposits under favorable conditions and to predict their oil and gas potential. The CDP method is also used in the study of ore deposits, solving problems of engineering geology.

Prospects for further improvement of the CDP method are associated with the development of observation and data processing techniques that provide a significant increase in its resolution, detail and accuracy of reconstructing images of three-dimensional complex geological objects; with the development of methods for the geological and geophysical interpretation of dynamic sections on a structural-formational basis in combination with data from other methods of field exploration geophysics and well research.

List of abbreviations

Introduction

1. General part

1.3 Tectonic structure

1.4 Oil and gas content

2.Special part

3.Design part

3.3 Apparatus and equipment

3.4 Methodology for processing and interpreting field data

4.Special task

4.1 AVO analysis

4.1.1 Theoretical aspects of AVO analysis

4.1.2 AVO classification of gas sands

4.1.3 AVO crossplotting

4.1.4 Elastic inversion in AVO analysis

4.1.5 AVO analysis in an anisotropic environment

4.1.6 Examples of practical application of AVO analysis

Conclusion

List of sources used

stratigraphic seismic field anisotropic

List of abbreviations

GIS-geophysical surveys of wells

MOB-method of the reflected wave

CDP method total point depth

Oil and gas complex

Oil and Gas Region

NGR-gas-bearing region

OG-reflecting horizon

CDP-common depth point

PV item explosion

PP-point of reception

s/n-seismic party

hydrocarbons

Introduction

This bachelor's thesis provides for the substantiation of CDP-3D seismic surveys in the Vostochno-Michayuskaya area and consideration of AVO-analysis as a special issue.

Seismic surveys and drilling data carried out in recent years have established the complex geological structure of the work area. Further systematic study of the East Michayu structure is necessary.

The work provides for the study of the area in order to clarify the geological structure of the CDP-3D seismic survey.

Bachelor's thesis consists of four chapters, introduction, conclusion, set out on pages of text, contains 22 figures, 4 tables. The bibliographic list contains 10 titles.

1. General part

1.1 Physical and geographical outline

The Vostochno-Michayuskaya area (Figure 1.1) is administratively located in the Vuktyl region.

Figure 1.1 - Map of the area of ​​the East Michayu area

Not far from the study area is the city of Vuktyl and the village of Dutovo. The area of ​​work is located in the Pechora River basin. The area is a hilly, gently undulating plain, with pronounced valleys of rivers and streams. The work area is swampy. The climate of the region is sharply continental. Summers are short and cool, winters are severe with strong winds. Snow cover is established in October and disappears at the end of May. In terms of seismic work, this area belongs to the 4th category of difficulty.

1.2 Lithological and stratigraphic characteristics

The lithological and stratigraphic characteristics of the section (Figure 1.2) of the sedimentary cover and foundation are given based on the results of drilling and seismic logging of wells 2-, 4-, 8-, 14-, 22-, 24-, 28-Michayu, 1 - S. Savinobor, 1 - Dinyu-Savinobor.

Figure 1.2 - Lithological and stratigraphic section of the Vostochno-Michayuskaya area

Paleozoic erathema - PZ

Devonian - D

Middle Devonian - D 2

Terrigenous formations of the Middle Devonian, Givetian Stage unconformably overlie the carbonate rocks of the Silurian sequence.

Deposits of the Givetian stage with a thickness of wells 1-Dinyu-Savinobor 233 m is represented by clays and sandstones in the volume of the Stary Oskol superhorizon (I - in the reservoir).

Upper Devonian - D 3

The Upper Devonian is distinguished in the volume of the Frasnian and Famennian stages. Fran is represented by three sub-tiers.

The deposits of the Lower Frasnian are formed by the Yaran, Dzhier, and Timan horizons.

Frasnian - D 3 f

Upper Franzian Substage - D 3 f 1

Yaransky horizon - D 3 jr

The section of the Yaran horizon (88 m thick in Q. 28-Mich.) is composed of sandy layers (from bottom to top) V-1, V-2, V-3 and interstratal clays. All layers are not consistent in composition, thickness and number of sand interlayers.

Jyers skyline - D 3 dzr

Clayey rocks occur at the base of the Dzhyer horizon, and sandy beds Ib and Ia are distinguished higher along the section, separated by a clay unit. The thickness of the jier varies from 15 m (KV. 60 - Yu.M.) to 31 m (KV. 28 - M.).

Timan horizon - D 3 tm

Deposits of the Timan horizon, 24 m thick, are composed of clayey-siltstone rocks.

Middle Fransian Substage - D 3 f 2

The Middle Fransian substage is represented in the volume of the Sargaev and Domanik horizons, which are composed of dense, silicified, bituminous limestones with interbeds of black shales. The thickness of the sargay is 13 m (borehole 22-M) - 25 m (borehole 1-Tr.), domanik - 6 m in the well. 28-M. and 38 m in well 4-M.

Upper Frasnian - D 3 f 3

The undivided Vetlasyan and Sirachoi (23 m), Evlanovsk and Liven (30 m) deposits form the section of the Upper Frasnian substage. They are formed by brown and black limestones interbedded with shale.

Famennian - D 3 fm

The Famennian stage is represented by the Volgograd, Zadonsk, Yelets, and Ust-Pechora horizons.

Volgograd horizon - D 3 vlg

Zadonsky horizon - D 3 zd

The Volgograd and Zadonsk horizons are composed of clay-carbonate rocks 22 m thick.

Yelets horizon - D 3 el

The deposits of the Yelets horizon are formed by organogenic-detrital limestone areas, in the lower part by strongly clayey dolomites, at the base of the horizon there are marls and calcareous, dense clays. The thickness of the deposits varies from 740 m (wells 14-, 22-M) to 918 m (well 1-Tr.).

Ust-Pechora horizon - D 3 up

The Ust-Pechora horizon is represented by dense dolomites, black argillite-like clays, and limestones. Its thickness is 190m.

Carboniferous system - C

Above unconformity deposits of the Carboniferous system occur in the volume of the lower and middle sections.

Lower Carboniferous - C 1

Visean - C 1 v

Serpukhovian - C 1 s

The lower section is composed of the Visean and Serpukhovian stages, formed by limestones with clay interbeds, with a total thickness of 76 m.

Upper Carboniferous Division - C 2

Bashkirian - C 2 b

Moscow Stage - C 2 m

The Bashkirian and Moscow stages are represented by clay-carbonate rocks. The thickness of the Bashkir deposits is 8 m (borehole 22-M.) - 14 m (borehole 8-M.), and in the well. 4-, 14-M. they are missing.

The thickness of the Moscow stage varies from 24 m (borehole 1-Tr) to 82 m (borehole 14-M).

Permian system - R

Moscow deposits are unconformably overlain by Permian deposits in the volume of the lower and upper sections.

Nizhnepermsky department - R 1

The lower section is presented in full and is composed of limestones and clayey marls, and in the upper part - clays. Its thickness is 112m.

Upper Permian department - R 2

The upper section is formed by the Ufa, Kazan and Tatar stages.

Ufimian - P 2 u

The Ufim deposits with a thickness of 275 m are represented by intercalation of clays and sandstones, limestones and marls.

Kazanian - P 2 kz

The Kazanian stage is composed of dense and viscous clays and quartz sandstones; there are also rare interlayers of limestones and marls. The layer thickness is 325 m.

Tatarian - P 2 t

The Tatarian stage is formed by terrigenous rocks 40 m thick.

Mesozoic erathema - MZ

Triassic system - T

The Triassic deposits in the volume of the lower section are composed of alternating clays and sandstones with a thickness of 118 m (well 107) - 175 m (well 28-M.).

Jurassic - J

The Jurassic system is represented by terrigenous formations with a thickness of 55 m.

Cenozoic erathema - KZ

Quaternary - Q

The section is completed by loams, sandy loams and sands of Quaternary age 65 m thick in well 22-M. and 100 m in well 4-M.

1.3 Tectonic structure

In tectonic terms (Figure 1.3), the area of ​​work is located in the central part of the Michayu-Pashninsky swell, which corresponds to the Ilych-Chiksha fault system along the foundation. The fault system is also reflected in the sedimentary cover. Tectonic disturbances in the work area are one of the main structural-forming factors.

Figure 1.3 - Copy from the tectonic map of the Timano-Pechora province

Three zones of tectonic disturbances were identified on the area of ​​work: western and eastern submeridional strike, and, in the southeast, the area of ​​northeast strike.

Tectonic disturbances observed in the west of this area can be traced along all reflectors, and disturbances in the east and southeast fade, respectively, in the Famennian and Frasnian times.

The tectonic faults in the western part are a graben-like trough. The sagging of horizons is most clearly seen on profiles 40990-02, 40992-02, -03, -04, -05.

The amplitude of the vertical displacement along the horizons ranges from 12 to 85 m. In plan view, the faults are oriented northwest. They stretch in the southeast direction from the reporting area, limiting the Dinya-Savinobor structure from the west.

Faults probably separate the axial part of the Michayu-Pashninskii swell from its eastern slope, which is characterized by continuous eastward subsidence of sediments.

In geophysical fields g, disturbances correspond to intense zones of gradients, the interpretation of which made it possible to single out a deep fault here, separating the Michayu-Pashninskaya zone of uplifts along the basement from the relatively lowered Lemyu step and being, probably, the main structure-forming fault (Krivtsov K.A., 1967 , Repin E.M., 1986).

The western zone of tectonic faults is complicated by northeast-trending feathering faults, due to which separate uplifted blocks are formed, as on profiles 40992-03, -10, -21.

The amplitude of the vertical displacement along the horizons of the eastern fault zone is 9-45 m (project 40990-05, station 120-130).

The southeastern fault zone is represented by a graben-like trough, the amplitude of which is 17–55 m (prospect 40992–12, site 50–60).

The western tectonic zone forms an elevated near-fault structural zone, consisting of several tectonically limited folds - Srednemichayuskaya, East Michayuskaya, Ivan-Shorskaya, Dinyu-Savinoborskaya structures.

The deepest horizon OG III 2-3 (D 2-3), on which structural constructions were made, is confined to the boundary between the Upper Devonian and Middle Devonian deposits.

Based on structural constructions, analysis of time sections and drilling data, the sedimentary cover has a rather complex geological structure. Against the background of the submonocline subsidence of the layers in the east direction, the East Michayu structure is distinguished. It was first identified as an open complication of the "structural nose" type with materials s\n 8213 (Shmelevskaya I.I., 1983). Based on the work of the 1989-90 season. (S\n 40990) the structure is presented as a fault fold, contoured along a sparse network of profiles.

Reporting data established the complex structure of the East Michayu structure. According to OG III 2-3, it is represented by a three-dome, linearly elongated, northwest-trending anticlinal fold, the dimensions of which are 9.75 × 1.5 km. The northern dome has an amplitude of 55 m, the central one - 95 m, and the southern one - 65 m. From the west, the East Michayu structure is limited by a graben-like trough of northwestern strike, from the south - by a tectonic fault with an amplitude of 40 m. In the north, the East Michayu anticline fold is complicated by an uplifted block (project nos. 40992-03), and in the south - a subsided block (projects 40990-07, 40992-11), due to feathering disturbances of the northeast strike.

To the north of the East Michayu uplift, the Middle Michayu near-fault structure was revealed. We assume that it closes to the north of the reporting area, where earlier work was carried out with / p 40991 and structural constructions were made along reflecting horizons in Permian deposits. The Middle Michayu structure was considered within the East Michayu uplift. According to the work with \ n 40992, the presence of a deflection between the East Michayu and Srednemichayu structures on the project 40990-03, 40992-02 was revealed, which is also confirmed by the reporting works.

In the same structural zone with the uplifts discussed above, there is the Ivan-Shorskaya anticline structure, identified by works s\n 40992 (Misyukevich N.V., 1993). From the west and south it is framed by tectonic faults. The dimensions of the structure according to OG III 2-3 are 1.75×1 km.

To the west of the Srednemichayuskaya, Vostochno-Michayuskaya, and Ivan-Shorskaya structures, there are the South-Lemyuskaya and Yuzhno-Michayuskaya structures, which are affected only by the western ends of the reported profiles.

Southeast of the South-Michayu structure, a low-amplitude East-Tripanyel structure was revealed. It is represented by an anticline fold, the dimensions of which according to OG III 2-3 are 1.5×1 km.

In the western marginal part of the submeridional-trending graben in the north of the reporting area, small near-fault structures are isolated. To the south, similar structural forms are formed due to small tectonic faults of various strikes, which complicate the graben zone. All these small structures in the blocks lowered relative to the East Michayu uplift are united by us under the general name of the Central Michayu structure and require further seismic exploration.

Reference point 6 is associated with OG IIIf 1 at the top of the Yaran horizon. Structural plan of reflecting horizon IIIf 1, inherited from OG III 2-3. The dimensions of the East Michayu near-fault structure are 9.1 × 1.2 km, in the contour of the isohypse - 2260 m, the northern and southern domes are distinguished with an amplitude of 35 and 60 m, respectively.

The dimensions of the Ivan-Shorskaya near-fault fold are 1.7 × 0.9 km.

The structural map of OG IIId reflects the behavior of the base of the Domanik horizon of the Middle Frasnian substage. In general, there is an uplift of the structural plan to the north. To the north of the reporting area, the base of the domanik was exposed by well No. 2-Sev.Michayu, 1-Sev.Michayu at absolute elevations - 2140 and - 2109 m, respectively, to the south - in the borehole. 1-Dinyu-Savinobor at the mark - 2257 m. The East Michayu and Ivan-Shor structures occupy an intermediate hypsometric position between the North-Michayu and Dinyu-Savinobor structures.

At the level of the Domanik horizon, the feathering disturbance at Project 40992-03 fades out; instead of the uplifted block, a dome has formed, covering the adjacent profiles 40990-03, -04, 40992-02. Its dimensions are 1.9 × 0.4 km, the amplitude is 15 m. To the south of the main structure, to another feathering fault on project 40992-10, a small dome closes with an isohypse of -2180 m. Its dimensions are 0.5 × 0.9, the amplitude is 35 m. The Ivan-Shor structure is located 60 m below the Vostochno-Michayuskaya.

The structural plan of the OG Ik confined to the top of the carbonates of the Kungurian stage differs significantly from the structural plan of the underlying horizons.

The graben-like trough of the western fault zone on the time sections has a cup-like shape; in connection with this, the structural plan of the OG Ik was restructured. The shielding tectonic faults and the arch of the East Michayu structure are shifting to the east. The size of the East Michayu structure is much smaller than in the underlying deposits.

The tectonic disturbance of the northeast strike breaks the East Michayu structure into two parts. Two domes stand out in the contour of the structure, and the amplitude of the southern one is greater than that of the northern one and is 35 m.

To the south is the Ivan-Shorsky fault uplift, which is now a structural nose, in the north of which a small dome stands out. The fault is fading, screening the Ivan-Shor anticline in the south along the lower horizons.

The eastern flank of the South Lemew structure is complicated by a slight tectonic disturbance of the submeridional strike.

Throughout the area there are small rootless tectonic disturbances, with an amplitude of 10-15 m, which do not fit into any system.

Productive at the Severo-Savinoborsky, Dinyu-Savinoborsky, Michayusky deposits, the sandy reservoir V-3 is located below the benchmark 6, with which OG IIIf1 is identified, by 18-22 m, and in the well. 4-Mich. at 30 m.

On the structural plan of the top of the V-3 formation, the highest hypsometric position is occupied by the Michayuskoye field, the northeastern part of which is confined to the South Lemyu structure. The WOC of the Michayuskoye field runs at a level of - 2160 m (Kolosov V.I., 1990). The East Michayu structure closes with an isohypse - 2280 m, an uplifted block at a level of - 2270 m, a lowered block at the southern end at a level of - 2300 m.

At the level of the Vostochno-Michayu structure, to the south there is the Severo-Savinoborskoye field with OWC at a level of - 2270 m. 1-Dinyu-Savinobor is defined at the level of - 2373 m.

Thus, the East Michayu structure, which is located in the same structural zone as the Dinya-Savinobor one, is much higher than it and may well be a good trap for hydrocarbons. The screen is a graben-shaped trough of northwestern strike of an asymmetric shape.

The western side of the graben runs along low-amplitude normal faults, except for some profiles (projects 40992-01, -05, 40990-02). Violations of the eastern side of the graben, the most subsided part of which is located at pr. 40990-02, 40992-03, are high-amplitude. According to them, the alleged permeable formations are in contact with the Sargaev or Timan formations.

To the south, the disturbance amplitude decreases and, at the level of profile 40992-08, the graben closes in the south. Thus, the southern periclinal of the Vostochno-Michayuskaya structure is in the lowered block. In this case, the V-3 formation can contact, by disturbance, with interstratal clays of the Yaran horizon.

To the south in this zone is the Ivan-Shorskaya near-fault structure, which is crossed by two meridional profiles 13291-09, 40992-21. The absence of seismic profiles across the strike of the structure does not allow us to judge the reliability of the object identified by s\n 40992.

The graben-like trough, in turn, is broken by tectonic faults, due to which isolated uplifted blocks are formed within it. They are named by us as the Central Michayu structure. On profiles 40992-04, -05, fragments of the East Michayu structure were reflected in the lowered block. There is a small low-amplitude structure at the intersection of profiles 40992-20 and 40992-12, which we named East Trypanyelskaya.

1.4 Oil and gas content

The area of ​​work is located in the Izhma-Pechora oil and gas region within the Michayu-Pashninsky oil and gas region.

At the fields of the Michayu-Pashninsky region, a wide complex of terrigenous-carbonate deposits from the Middle Devonian to the Upper Permian, inclusive, is oil-bearing.

Near the area under consideration are the Michayuskoye and Yuzhno-Michayuskoye deposits.

Deep prospecting and exploratory drilling, carried out in 1961 - 1968. at the Michayuskoye field, wells No. 1-Yu. tiers. The deposit is layered, arched, partially waterfowl. The height of the deposit is about 25 m, the dimensions are 14 × 3.2 km.

At the Michayuskoye field, commercial oil-bearing capacity is associated with sandy formations at the base of the Kazanian stage. For the first time, oil from the Upper Permian deposits at this field was obtained in 1982 from well 582. The oil-bearing capacity of the R 2 -23 and R 2 -26 formations was established by testing in it. Oil deposits in the P 2 -23 formation are confined to sandstones, presumably of channel genesis, stretching in the form of several strips of submeridional strike through the entire Michayuskoye field. Oil-bearing capacity is established in the well. 582, 30, 106. Light oil, with a high content of asphaltenes and paraffin. The deposits are confined to a trap of a structural-lithological type.

Oil deposits in the layers P 2 -24, P 2 -25, P 2 -26 are confined to sandstones, presumably of channel genesis, stretching in the form of strips through the Michayuskoye field. The width of the strips varies from 200 m to 480 m, the maximum thickness of the seam is from 8 to 11 m.

Reservoir permeability is 43 mD and 58 mD, porosity is 23% and 13.8%. Starting stocks cat. A + B + C 1 (geol. / izv.) are equal to 12176/5923 thousand tons, category C 2 (geol. / izv.) 1311/244 thousand tons. Remaining reserves as of 01.01.2000 in categories А+В+С 1 are 7048/795 thousand tons, in category С 2 1311/244 thousand tons, cumulative production is 5128 thousand tons.

The Yuzhno-Michayuskoye oil field is located 68 km northwest of the city of Vuktyl, 7 km from the Michayuskoye field. It was discovered in 1997 by well 60 - Yu.M., in which an oil inflow of 5 m 3 /day was obtained from the interval 602 - 614 m according to PU.

The reservoir oil deposit, lithologically shielded, confined to the sandstones of the P 2 -23 formation of the Kazanian stage of the Upper Permian.

The depth of the formation roof in the crest is 602 m, the reservoir permeability is 25.4 mD, and the porosity is 23%. The oil density is 0.843 g/cm 3 , the viscosity in reservoir conditions is 13.9 MPa. s, the content of resins and asphaltenes 12.3%, paraffins 2.97%, sulfur 0.72%.

Initial stocks are equal to residual stocks on 01.01.2000. and amount to 1,742/112 thousand tons for categories A+B+C, and 2,254/338 thousand tons for category C.

At the Dinyu-Savinoborskoye field, an oil deposit in terrigenous deposits of the V-3 formation of the Yaran horizon of the Frasnian stage of the Upper Devonian was discovered in 2001. well 1-Dinyu-Savinobor. In the well section, 4 objects were tested (Table 1.2).

When testing the interval 2510-2529 m (formation V-3), an inflow (solution, filtrate, oil, gas) was obtained in the amount of 7.5 m 3 (of which oil - 2.5 m 3).

When testing the interval 2501-2523 m, oil was obtained with a flow rate of 36 m 3 / day through a choke with a diameter of 5 mm.

When testing the overlying reservoirs of the Yaran and Dzhier horizons (layers Ia, Ib, B-4) (test interval 2410-2490 m), no oil shows were observed. A solution was obtained in a volume of 0.1 m 3.

To determine the productivity of the V-2 formation, a test was carried out in the interval of 2522-2549.3 m. As a result, a solution, filtrate, oil, gas and formation water in the amount of 3.38 m 3 were obtained, of which 1.41 m3 were due to leaks in the tool 3, inflow from the reservoir - 1.97 m 3.

When studying the Lower Permian deposits (test interval 1050 - 1083.5 m), a solution in the volume of 0.16 m 3 was also obtained. However, in the process of drilling, according to the core data, signs of oil saturation were noted in the indicated interval. In the interval 1066.3-1073.3 sandstones are inequigranular, lenticular. Oil effusions were observed in the middle of the interval, 1.5 cm - a layer of oil-saturated sandstone. In the intervals of 1073.3-1080.3 m and 1080.3-1085 m, interlayers of sandstones with oil effusions and thin (in the interval of 1080.3-1085 m, core removal 2.7 m) interlayers of polymictic oil-saturated sandstone are also noted.

Signs of oil saturation according to the core data in the well 1-Dinyu-Savinobor were also noted in the top of the member of the Zelenetsky horizon of the Famennian stage (core sampling interval 1244.6-1253.8 m) and in layer Ib of the Dzhiersky horizon of the Frasnian stage (core sampling interval 2464.8-2470 m).

In reservoir V-2 (D3 jr) there are sandstones with hydrocarbon odor (core sampling interval 2528.7-2536 m).

Information about the results of testing and oil shows in the wells is given in tables 1.1 and 1.2.

Table 1.1 - Well testing results

			formation.	Test results.
				1 object. Mineralized water inflow Q=38 m 3 /day according to PU.
				2 object. Min. water Q \u003d 0.75 m 3 / day according to PU.
				3 object. No inflow received.
				1 object. Min. water Q \u003d 19.6 m 3 / day.
				2 object. Minor inflow min. water Q \u003d 0.5 m 3 / day.
				1 object. IP reservoir min. water with an admixture of the filtrate solution Q=296 m 3 /day.
				2 object. IP reservoir min. water with the smell of hydrogen sulfide, dark green.
				3 object. Min. water Q \u003d 21.5 m 3 / day.
				4 object. Min. water Q \u003d 13.5 m 3 / day.
				In the column, the free flow of oil is 10 m 3 /day.
				Oil Q=21 t/day at 4 mm choke.
				1 object. Industrial oil inflow Q=26 m 3 /day on a 4 mm choke.
				1 object. Oil gusher Q \u003d 36.8 m 3 / day on a 4 mm fitting.
				Oil inflow 5 m 3 /day according to PU.
				3, 4, 5 objects. Weak oil inflow Q \u003d 0.1 m 3 / day.
				IP oil 25 m 3 in 45 min.
				The initial oil flow rate is 81.5 tons/day.
				5.6 m 3 of oil in 50 minutes.
				The initial oil flow rate is 71.2 tons/day.
				Oil Q beg. =66.6 t/day.
				Oil inflow Q=6.5 m 3 /hour, P pl. =205 atm.
				The initial oil flow rate is 10.3 t/day.
				Oil Q \u003d 0.5 m 3 / hour, R pl. =160 atm.
				Mineral water with films of oil.
				Solution, filtrate, oil, gas. Inflow volume 7.5 m 3 (of which oil 2.5 m 3). R sq. =27.65 MPa.
				Solution, filtrate, oil, gas, formation water. V pr. \u003d 3.38 m 3, R pl. =27.71 MPa.
				Oil flow rate 36 m 3 /day, diam. PC. 5 mm.
				No inflow received.

Table 1.2 - Information about oil shows

		Interval		The nature of manifestations.
				Limestones with oil smears in caverns and pores.
				Films of oil during drilling.
				According to GIS, oil-saturated sandstone.
				Limestone with suture joints filled with bituminous clay.
				Oil-saturated core.
				Alternation of oil-saturated sandstones, siltstones, thin layers of clays.
				Oil-saturated core.
				Oil-saturated polymictic sandstones.
				Water-saturated sandstones.
				Oil-saturated limestones.
				The limestone is cryptocrystalline, with rare cracks containing bituminous material.
				Argillite, limestone. Mid-interval oil effusion; 1.5 cm - layer of oil-saturated sandstone.
				The sandstone is inequigranular and fine-grained with oil exudates.
				Limestone and individual layers of oil-saturated sandstone.
				Alternation of dolomite and dolomitic limestone with oil exudates.
				Argillite with effusions and films of oil along cracks; siltstone with the smell of oil.
				Alternation of sandstones with effusions and oil stains.
				Alternation of sandstones with HC odor and mudstones with bitumen interspersed.
				Fine-grained sandstones with hydrocarbon odor, bituminous along fissures.
				Limestone with oil exudates and hydrocarbon smell; sandstone and mudstone with oil exudates.
				Dense and strong sandstone with a hydrocarbon smell.
				Alternation of quartz sandstone with hydrocarbon smell, siltstone and mudstone.
				Quartz sandstones with low hydrocarbon odor.

2. Special part

2.1 Geophysical work carried out in this area

The report was compiled based on the results of reprocessing and reinterpretation of seismic data obtained in the northern block of the Dinyu-Savinobor field in different years by seismic crews 8213 (1982), 8313 (1984), 41189 (1990), 40990 (1992), 40992 (1993) according to the agreement between Kogel LLC and Dinyu LLC. The methodology and technique of work is shown in Table 2.1.

Table 2.1 - Information about the methodology of field work

			" Progress"	"Progress - 2"	"Progress - 2"
Observation system	Central	Central naya	flank	flank	flank
Source Options
	Explosive	Explosive	non-explosive"falling weight" - SIM	Non-explosive "drop weight" - SIM	Non-explosive "Yenisei - SAM"
Number of wells in a group
Charge amount
Distance between shots
Placement Options
multiplicity
Geophone grouping	26 joint ventures based on 78 m	26 joint ventures based on 78 m	12 joint ventures on a base of 25 m	11 joint ventures on the base of 25 m	11 joint ventures on the base of 25 m
Distance between PP
Minimum explosion-device distance
Maximum distance explosion-device

The Vostochno-Michayu tectonic-limited structure identified by the works s / p 40991 was transferred to drilling on the Lower Frasnian, Lower Famennian and Lower Permian deposits in 1993 s / p 40992. Seismic surveys were generally focused on the study of the Permian part of the section, structural constructions in the lower part of the section performed only on the reflecting horizon III f 1 .

To the west of the work area are the Michayuskoye and Yuzhno-Michayuskoye oil fields. The commercial oil and gas potential of the Michayuskoye field is associated with the Upper Permian deposits, the oil deposit is contained in the sandstones of the V-3 formation at the top of the Yaran horizon.

South-east of the Vostochno-Michayu structure in 2001, the 1-Dinyu-Savinobor well discovered an oil deposit in the Lower Frasnian deposits. The Dinyu-Savinobor and East Michayu structures are located in the same structural zone.

In connection with these circumstances, it became necessary to revise all available geological and geophysical materials.

The reprocessing of seismic data was carried out in 2001 by Tabrina V.A. in the ProMAX system, the volume of reprocessing was 415.28 km.

Pre-processing consisted of converting the data to the internal ProMAX format, assigning the geometry, and restoring the amplitudes.

Interpretation of the seismic material was carried out by the leading geophysicist I.Kh. Mingaleeva, geologist E.V. Matyusheva, category I geophysicist N.S. The interpretation was carried out in the Geoframe exploration system on the SUN 61 workstation. The interpretation included the correlation of reflective horizons, the construction of isochron, isohyps, and isopach maps. The workstation was loaded with digitized logs for wells 14-Michayu, 24-Michayu. To recalculate the logging curves to the time scale, the velocities obtained from the seismic logging of the corresponding wells were used.

The construction of isochron, isohyps, and isopach maps was carried out automatically. If necessary, they were corrected manually.

Velocity models needed to transform isochrone maps into structural ones were determined from drilling and seismic data.

The isohypse cross section was determined by the construction error. In order to preserve the features of the structural plans and for better visualization, the isohypse section was taken to be 10 m along all reflective horizons. Map scale 1:25000. Stratigraphic confinement of reflecting horizons was carried out according to seismic logging of wells 14-,24-Michayu.

6 reflecting horizons were traced on the area. Structural constructions were presented for 4 reflecting horizons.

OG Ik is confined to benchmark 1, identified by analogy with the Dinyu-Savinobor well in the upper Kungurian, 20-30 m below the Ufim deposits (Figure 2.1). The horizon is well correlated in the positive phase, the reflection intensity is low, but the dynamic features are consistent over the area. The next reflecting horizon II-III is identified with the boundary of the Carboniferous and Devonian deposits. GO is quite easily recognized on the profiles, although in places there is interference of two phases. At the eastern ends of the latitudinal profiles, an additional reflection appears above OG II-III, which wedges out to the west in the form of a plantar overlap.

OG IIIfm 1 is confined to benchmark 5, identified in the lower part of the Yeletsk Horizon of the Lower Famennian. In wells 5-M., 14-M, benchmark 5 coincides with the bottom of the Yelets horizon identified by the TP NRC, in other wells (2,4,8,22,24,28-M) it is 3-10 m higher than the official breakdown of the bottom D 3 el. The reflecting horizon is a reference horizon, has pronounced dynamic features and high intensity. Structural constructions for OG IIIfm 1 are not provided by the program.

OG IIId is identified with the base of the Domanik deposits and is confidently correlated in time sections in the negative phase.

Reference point 6 at the top of the Lower Franian Yaran horizon is associated with OG IIIf 1 . Benchmark 6 stands out quite confidently in all wells 10-15m below the base of the Dzher deposits. Reflecting horizon IIIf 1 is tracked well, despite the fact that it has a low intensity.

Productive at the Michayuskoye, Dinyu-Savinoborskoye fields, the V-3 sandy reservoir is located 18-22 m below the IIIf 1 OG, only in the 4-M well. the thickness of the deposits enclosed between the OG IIIf 1 and the V-3 formation is increased to 30 m.

Figure 2.1 - Comparison of sections of wells 1-C. Michayu, 24-Michayu, 14-Michayu and snap reflective horizons

The next reflecting horizon III 2-3 is weakly expressed in the wave field, traced near the top of the Middle Devonian terrigenous deposits. OG III 2-3 is correlated in negative phase as an erosion surface. In the south-west of the reporting area, there is a decrease in the temporal thickness between OG IIIf 1 and III 2-3, which is especially clearly seen on profile 8213-02 (Figure 2.2).

Structural constructions (Figures 2.3 and 2.4) were made along the reflectors Ik, IIId, IIIf 1 , III 2-3 , an isopach map was built between OG IIId and III 2-3 , a structural map is presented along the top of the B-3 sand bed, for the entire Dinho - Savinoborskoye deposit.

Figure 2.2 - Fragment of the time section along the profile 8213-02

2.2 Results of geophysical surveys

As a result of reprocessing and reinterpretation of seismic data on the northern block of the Dinyu-Savinobor field.

We studied the geological structure of the northern block of the Dinyu-Savinoborskoye field based on the Permian and Devonian deposits,

Figure 2.3 - Structural map along the reflecting horizon III2-3 (D2-3)

Figure 2.4 - Structural map along the reflecting horizon III d (D 3 dm)

- traced and linked across the area 6 reflectors: Ik, II-III, IIIfm1 , IIId, IIIf1 , III2-3 ;

Performed structural constructions on a scale of 1:25000 for 4 OG: Ik, IIId, IIIf1, III2-3;

A general structural map was built along the top of the B-3 formation for the Dinyu-Savinobor structure and the northern block of the Dinyu-Savinobor field, and an isopach map between OG IIId and III2-3;

We built deep seismic sections (horizon scales 1:12500, ver. 1:10000) and seismo-geological sections (horizon scales 1:25000, ver. 1:2000);

We built a comparison scheme for the Lower Frasnian deposits by wells in the Michayuskaya area, well No. 1-Dinyu-Savinobor and 1-Tripanyel on a scale of 1:500;

Clarified the geological structure of the East Michayu and Ivan-Shor structures;

Revealed the Middle Michayu, Central Michayu, East Trypanyol structures;

A NE-trending graben-like trough was traced, which is a screen for the northern block of the Dinyu-Savinobor structure.

In order to study the oil potential of the Lower Frasnian deposits within the central block of the East Michayu structure, drill a prospecting well No. 3 on the profile 40992-04 pk 29.00 with a depth of 2500 m until the opening of the Middle Devonian deposits;

On the southern block - exploratory well No. 7 at the cross of profiles 40990-07 and 40992 -21 with a depth of 2550 m;

On the northern block - exploratory well No. 8 profile 40992-03 pk 28.50 with a depth of 2450 m;

Carrying out detailed seismic surveys within the Ivan-Shor structure;

To carry out reprocessing and reinterpretation of seismic surveys on the South-Michayuskaya and Srednemichayuskaya structures.

2.3 Rationale for choosing 3D seismic

The main reason that justifies the need to use a rather complex and rather expensive 3D areal seismic technology at the exploration and detailing stages is the transition in most regions to the study of structures and deposits with more and more complex reservoirs, which leads to the risk of drilling empty wells. It has been proven that with an increase in spatial resolution by more than an order of magnitude, the cost of 3D works in comparison with detailed 2D survey (~ 2 km/km 2) increases only 1.5-2 times. At the same time, the detail and total amount of 3D shooting information is higher. A practically continuous seismic field will provide:

· Higher detail description of structural surfaces and mapping accuracy compared to 2D (errors are reduced by 2-3 times and do not exceed 3-5 m);

· Unambiguity and reliability of tracing by area and volume of tectonic faults;

· Seismic facies analysis will provide identification and tracking of seismic facies in volume;

· Possibility of interpolation into the interwell space of reservoir parameters (layer thickness, porosity, boundaries of reservoir development);

· Refinement of oil and gas reserves by detailing the structural and estimated characteristics.

This indicates the possible economic and geological feasibility of using a three-dimensional survey on the East Michayu structure. When choosing economic feasibility, it must be borne in mind that the economic effect of applying 3D to the entire complex of exploration and development of fields also takes into account:

· growth of reserves in categories C1 and C2;

· savings by reducing the number of uninformative exploration and low-rate production wells;

· optimization of the development mode by refining the reservoir model;

· growth of C3 resources due to the identification of new objects;

· cost of 3D survey, data processing and interpretation.

3. Design part

3.1 Substantiation of the work methodology CDP - 3D

The choice of an observation system is based on the following factors: tasks to be solved, features of seismogeological conditions, technical capabilities, and economic benefits. The optimal combination of these factors determines the observation system.

In the Vostochno-Michayuskaya area, CDP-3D seismic surveys will be carried out in order to study in detail the structural-tectonic and lithofacies features of the structure of the sedimentary cover in sediments from Upper Permian to Silurian; mapping of zones of development of lithofacies heterogeneities and improved reservoir properties, discontinuous tectonic disturbances; study of the geological history of development based on paleostructural analysis; identification and preparation of oil-promising objects.

To solve the tasks, taking into account the geological structure of the region, the factor of minimal impact on the natural environment and the economic factor, an orthogonal observation system is proposed with excitation points located between the reception lines (i.e., with overlapping reception lines). Explosions in wells will be used as excitation sources.

3.2 Example of calculation of a "cross" observing system

The observation system of the "cross" type is formed by successive overlapping of mutually orthogonal arrangements, sources and receivers. Let us illustrate the principle of areal system formation on the following idealized example. Let us assume that the geophones (a group of geophones) are evenly distributed along the line of observation coinciding with the X axis.

Along the axis intersecting the arrangement of seismic receivers in the center, m is placed uniformly and symmetrically at the sources. The step of the sources of do and the seismic receivers of dx is the same. The signals generated by each source are received by all geophones of the array. As a result of such testing, a field of m 2 midpoints of reflection is formed. If we sequentially shift the arrangement of seismic receivers and the line of sources orthogonal to it along the X axis by a step dx and repeat the registration, then the result will be a multiple overlap of the band, the width of which is equal to half the excitation base. Sequential displacement of the excitation and reception base along the Y-axis by a step du leads to an additional - multiple overlap, and the total overlap will be. Naturally, in practice, more technologically advanced and economically sound variants of a system with mutually orthogonal lines of sources and receivers should be used. It is also obvious that the overlap ratio must be chosen in accordance with the requirements determined by the nature of the wave field and processing algorithms. As an example, Figure 3.1 shows an eighteen-fold areal system, for the implementation of which one 192-channel seismic station is used, which sequentially receives signals from 18 excitation pickets. Consider the parameters of this system. All 192 geophones (groups of geophones) are distributed on four parallel profiles (48 on each). The step dx between the reception points is 0.05 km, the distance d between the reception lines is 0.05 km. The step of Sy sources along the Y axis is 0.05 km. A fixed distribution of sources and receivers will be called a block. After receiving vibrations from all 18 sources, the block is shifted by a step This is how a strip is worked out along the X axis from the beginning to the end of the study area. The next lane of four reception lines is placed parallel to the previous one so that the distance between adjacent (nearest) reception lines of the first and second lanes is equal to the distance between the reception lines in the block (?y = 0.2 km). In this case, the source lines of the first and second bands overlap by half the excitation base. When working out the third band, the source lines of the second and third bands overlap by half, etc. Consequently, in this version of the system, the receiving lines are not duplicated, and at each source point (excluding the extreme ones) the signals are excited twice.

Let us write down the main relations that determine the parameters of the system and its multiplicity. To do this, following Figure 8, we introduce additional notation:

W - number of receiving lines,

m x - number of receiving points on each receiving line of the given block;

m y - the number of sources on each excitation line of the given block,

P is the width of the interval in the center of the excitation line, within which the sources are not placed,

L - offset (displacement) along the X axis of the source line from the nearest reception points.

In all cases, the intervals ?x, ?y, and L are multiples of the step dx. This ensures the uniformity of the network of midpoints corresponding to each source-receiver pair, i.e. do it! requirement of the condition necessary for the formation of seismograms of common midpoints (CMP). Wherein:

Ax=Ndx N=1, 2, 3…

tSy-MdyM=1, 2, 3…

L=q qxq=1, 2, 3…

Let us explain the meaning of the parameter P. The shift between the lines of the midpoints is equal to half the step? If the sources are uniformly distributed (there is no discontinuity), then for similar systems the overlap factor along the Y axis is equal to W (the number of receiving lines). To reduce the multiplicity of overlaps along the Y axis and to reduce costs due to a smaller number of sources, a gap is made in the center of the excitation line by a value P equal to:

Where, k = 1,2,3...

When k=1,2, 3, respectively, the overlap ratio decreases by 1, 2, 3, i.e. becomes equal to W-K.

The general formula relating the multiplicity of overlaps n y with the parameters of the system

hence the expression for the number of sources m y on one excitation line can be written as follows:

For the observation system (Figure 3.1), the number of sources on the excitation line is 18.

Figure 3.1 - Observation system of the "cross" type

It follows from expression (3.3) that since the step of the profiles? y is always a multiple of the step of sources dy, the number of sources t y for this type of system is an even number. Distributed on a straight line parallel to the Y axis symmetrically to the reception profiles included in this block, the excitation points either coincide with the reception points, or are shifted relative to the reception points by 1/2·dy. If the overlap multiplicity n y in a given block is an odd number, the sources always do not coincide with the receiving points. If n y is an even number, two situations are possible: ?y/du is an odd number, the sources coincide with the reception points, ?y/du is an even number, the sources are shifted relative to the reception points by dy/2. This fact should be taken into account when synthesizing the system (choosing the number of reception profiles W and the step? y between them), since it depends on whether the vertical times necessary to determine the static corrections will be recorded at the reception points.

The formula that determines the multiplicity of overlaps n x along the X axis can be written similarly to formula (3.2)

thus, the total multiplicity of overlaps n xy by area is equal to the product of n x and n y

In accordance with the accepted values ​​of m x, dx and? x, the multiplicity of overlaps n x along the X axis calculated by formula (3.4) is 6, and the total multiplicity n xy = 13 (Figure 3.2).

Figure 3.2 - Multiplicity of overlaps nx = 6

Along with the observation system, which provides for the overlapping of sources without overlapping of the receiving lines, systems are used in practice in which the excitation lines do not overlap, but part of the receiving lines is duplicated. Let us consider six receiving lines, on each of which seismic receivers receiving signals sequentially excited by sources are evenly distributed. When working out the second band, three reception lines are duplicated by the next block, and the source lines go as a continuation of the orthogonal profiles of the first band. Thus, the applied work technology does not provide for duplication of excitation points. With double overlapping of the receiving lines, the multiplicity n y is equal to the number of overlapping receiving lines. The full equivalent of a system of six profiles followed by an overlap of three receive lines is a system with overlapping sources, the number of which is doubled to achieve the same fold. Therefore, systems with overlapping sources are economically unprofitable, because. this technique requires a large amount of drilling and blasting.

Transition to 3D seismic.

The design of a 3D survey is based on the knowledge of a number of characteristics of the seismological section of the work area.

Information about the geoseismic section includes:

Multiplicity of shooting 2D

maximum depths of target geological boundaries

minimal geological boundaries

the minimum horizontal size of local geological objects

maximum frequencies of reflected waves from target horizons

average speed in the layer lying on the target horizon

time of registration of reflections from the target horizon

the size of the study area

To register the time field in MOGT-3D, it is rational to use telemetry stations. The number of profiles is selected depending on the multiplicity n y =u.

The distance between the common midpoints on the reflective surface along the X and Y axes determines the bin size:

The maximum allowable minimum offset of the source line is selected based on the minimum depth of the reflecting boundaries:

Minimum offset.

Maximum offset.

To ensure the multiplicity n x, the distance between the excitation lines?x is determined:

For the recording unit, the distance between the receiving lines? y:

Taking into account the technology of work with double overlapping of the receiving line, the number of sources m y in one block to ensure the multiplicity n y:

Figure 3.3 - Multiplicity ny =2

Based on the results of planning a 3D survey, the following data set is obtained:

distance between channels dx

the number of active channels on one receiving line m x

total number of active channels m x u

minimum offset Lmin

bin size

total multiplicity n xy

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