An amplitude compensation method and system for seismic CRP gathers oriented towards pre-stack inversion

Abstract

This invention relates to an amplitude compensation method and system for seismic CRP gathers oriented towards pre-stack inversion. The method includes obtaining an actual wellbore AVO forward modeling gather using acquired well logging data and identifying top and bottom marker reflector layers; determining the effective incident angle range of each marker reflector layer in the seismic CRP gather based on AVO response characteristics, thereby obtaining the gradient of the AVO fitting equation; dividing the seismic CRP gather into multiple sub-gathers according to the incident angle range to determine the target incident angle range; using the gradient as a known quantity to obtain the intercept to obtain the target AVO fitting equation; using the theoretical amplitude value and actual amplitude value obtained from the target fitting equation to obtain the amplitude compensation coefficients corresponding to each marker reflector layer; performing linear interpolation on the amplitude compensation coefficients corresponding to each top and bottom marker reflector layer to obtain the target segment compensation coefficient volume, thus obtaining the compensated seismic CRP gather. The amplitude compensation method according to this invention can solve the problem of poor compensation effect in existing high-fidelity amplitude compensation techniques.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas reservoir exploration technology, specifically relating to an amplitude compensation method and system for seismic CRP gathers oriented towards pre-stack inversion. Background Technology

[0002] With the increasing importance of complex and concealed oil and gas reservoirs, such as tight sandstone reservoirs, in driving the growth of oil and gas reserves in old oil and gas fields, high-fidelity seismic data amplitude has become a fundamental requirement for quantitative reservoir description and oil and gas prediction. The reliability of AVO (Amplitude Variation with Offset) information in seismic CRP gathers directly affects the accuracy of pre-stack inversion results, and consequently, the reliability of quantitative reservoir description and oil and gas prediction. Therefore, how to perform reasonable amplitude compensation for CRP gathers with high fidelity has become an important research topic in the field of oil and gas exploration technology.

[0003] Current methods for amplitude compensation of CRP gathers can be mainly divided into three categories:

[0004] The first method is the "planar statistical method." This involves first extracting a planar distribution map of the root-mean-square amplitude attribute using a small window of the same size along the target layer from the seismic stack data volume. Then, the mean amplitude is statistically analyzed by zone and zonation, and zone-specific amplitude correction is performed. This method can improve the consistency of amplitude energy levels between different zones. However, its drawbacks are: 1. The boundaries of different zones cannot be accurately defined, and the zone division results are subject to significant subjective factors; 2. Significant amplitude differences easily appear on both sides of the compensated boundary, failing to meet the requirements of quantitative reservoir description; 3. The amplitude values ​​of seismic traces corresponding to different incident angles are affected differently by the AVO gradient. Therefore, the amplitude compensation coefficients of different seismic traces within the same CRP gather differ. Using the same amplitude compensation coefficient for the entire CRP gather cannot reasonably correct the AVO characteristic trend of the CRP gather, which is detrimental to subsequent inversion work.

[0005] The second method is the "full offset extrapolation method." Its principle is based on the correspondence between the reflection amplitude and incident angle of each seismic trace in the actual CRP gather. The coefficients of the Zoeppritz approximation equation (usually the Shuey equation) are extracted using the least squares fitting method, thus obtaining the fitted AVO equation and deriving the theoretical reflection amplitude value and compensation coefficients. For example, Chinese invention patent application CN103954998A discloses a residual amplitude compensation method based on AVO characteristics. The drawback of this method is that the amplitude of seismic data within the near and far offset ranges is easily affected by noise interference and dynamic correction stretching distortion, resulting in poor fidelity. Therefore, the fitted AVO equation obtained based on seismic data within the full offset range has a large error, and there may even be a mismatch between the AVO characteristics and the actual drilling data, failing to meet the requirements for fidelity amplitude compensation.

[0006] Thirdly, there is the "well-controlled offset extrapolation method." This method incorporates well-controlled constraints in the process of obtaining the amplitude compensation coefficient. First, it generates a forward modeling gather of the actual drilled well using actual drilled well data. Then, based on the AVO response characteristics of the reflective layer in the forward modeling gather and the actual CRP gather near the well, it determines the effective incident angle range of the actual gather. Based on the actual seismic data within this incident angle range, it uses the least squares fitting method to obtain the fitted AVO equation. Then, it uses the theoretical reflection amplitude value obtained from the fitted AVO equation and the actual reflection amplitude value of the CRP gather to derive the reflection amplitude compensation coefficient. This method improves the matching degree of well-seismic data and is currently the most commonly used CRP gather amplitude compensation method. For example, Chinese invention patent application with publication number CN112462431A discloses a pre-stack gather amplitude compensation method based on well control and offset. The advantage of this method is that it can use the results of single-well forward modeling as the ideal compensation result. However, the disadvantages are: 1. The number of wells is too sparse relative to the entire work area. Many CRP gathers are far from the wells or located in areas without surrounding wells. Therefore, the compensation results of CRP gathers near the wells are known, and there is no need to calculate the compensation coefficient. On the other hand, CRP gathers in distant well areas are outside the constraint range of the well, and the compensation coefficient cannot be calculated. Thus, the AVO forward modeling gathers derived from actual drilling data only have constraining and guiding significance for the fidelity amplitude compensation of CRP gathers in the vicinity of the well. The statistical results of the planar distribution in the area show that the planar distribution density of actual drilled wells is much lower than the spatial sampling density of seismic data. Therefore, it is necessary to consider how to obtain the CRP gather compensation coefficient at the location between wells when using multiple well constraints. Otherwise, the fidelity of the CRP gather amplitude compensation results at a distance from the actual drilled wells within the work area cannot be guaranteed. 2. Vertically, only the fidelity compensation effect of the marker reflector layer and its adjacent reflector layer can be guaranteed. When the target reservoir is far from the marker reflector layer, the compensation coefficient calculated based on the marker reflector layer is prone to overcompensation or undercompensation of the reflection phase axis of the target reservoir. Taking continental tight sandstone reservoirs as an example, continental tight sandstone reservoirs have the characteristics of vertical gradation, planar segmentation, and discontinuous macroscopic distribution in spatial distribution, and cannot serve as marker reflector layers. If the marker reflector layer and the tight sandstone reservoir are far apart in vertical depth, the fidelity of the amplitude compensation result of the tight sandstone reservoir reflection amplitude can not be guaranteed by the amplitude compensation coefficient obtained based on the marker reflector layer. The main solution to the drawbacks of this method is to calculate the compensation coefficient at the well point using the single-well forward modeling results and the well-side CRP gather, and then interpolate between well points. However, this solution is not practical because there is no reasonable interpolation method. It cannot be used for quantitative calculation of compensation results, whether for seismic facies zoning or seismic facies constraints.

[0007] In summary, current methods for fidelity amplitude compensation of CRP gathers lack a method for obtaining amplitude compensation coefficients for CRP gathers in distant well areas. To avoid the problem of inter-well interpolation when using multiple wells, compensation coefficients are usually extracted from a single well and applied to the entire area. However, using a single well to extract compensation coefficients directly from the response characteristics to obtain the AVO fitting equation results in a large discrepancy between the intercept of the fitting equation and the actual situation, thus leading to poor fidelity amplitude compensation. Summary of the Invention

[0008] This invention provides an amplitude compensation method and system for seismic CRP gathers oriented towards pre-stack inversion, which solves the problem that the intercept of the fitted equation in the prior art differs greatly from the actual situation, resulting in poor compensation effect of fidelity amplitude compensation.

[0009] To address the aforementioned technical problems, this invention provides an amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion, comprising:

[0010] 1) Acquire seismic and well logging data, generate AVO forward modeling gathers of actual drilled wells based on the acquired well logging data, and determine the top and bottom marker reflection layers of the target interval;

[0011] 2) Compare the AVO response characteristics of each marker reflection layer in the actual well AVO forward model gather and the well-side CRP gather respectively, determine the effective incident angle range of each marker reflection layer in the well-side CRP gather that conforms to the response characteristics of the actual well AVO forward model gather, and obtain the effective incident angle range of each marker reflection layer in all seismic CRP gathers in the work area by comparing the effective incident angle range of all well-side CRP gathers in the work area. Based on the seismic data within this effective incident angle range, fit the AVO fitting equation of each marker reflection layer on each seismic CRP gather.

[0012] 3) Divide the seismic CRP gather into multiple sub-gathers according to the range of incident angles of reflected waves and stack them to obtain corresponding partial stacked data volumes. Compare and analyze the stacked data volumes of each part to determine the range of target incident angles with better amplitude fidelity on the top and bottom marker reflector layers.

[0013] 4) Using the gradient in the AVO fitting equation obtained in step 2) as a known quantity, the target AVO fitting equation of each marker reflection layer on the seismic CRP gather is obtained by fitting the seismic data within the target incident angle range.

[0014] 5) Based on the target AVO fitting equation of each marker reflector layer, the theoretical amplitude value of the corresponding seismic trace in each marker reflector layer is obtained. The amplitude compensation coefficient corresponding to each marker reflector layer is obtained by using the theoretical amplitude value and the actual amplitude value of the corresponding seismic trace.

[0015] 6) Interpolate the amplitude compensation coefficients corresponding to each marker reflection layer to obtain the compensation coefficient volume of the target segment, and then obtain the compensated seismic CRP gather.

[0016] The beneficial effects of the above technical solution are as follows: According to the amplitude compensation method of the present invention, the effective incident angle range of the well-side CRP gather of a single well is obtained, and by comparing the effective incident angle range of all well-side CRP gathers in the work area, the effective incident angle range of each marker reflection layer of all seismic CRP gathers in the work area is obtained, and then the AVO fitting equation of each marker reflection layer on each seismic CRP gather is obtained. In this case, reliable data obtained by multi-well constraint is used to fit and obtain the corresponding AVO fitting equation, thereby avoiding the problem of unreasonable interpolation that cannot be achieved. In addition, the amplitude compensation coefficient is calculated by using the top and bottom marker reflection layers, which can improve the fidelity of the amplitude compensation result at the reservoir location. Furthermore, based on the seismic CRP gathers divided into multiple sub-gathers according to the range of incident angles of reflected waves, a partial stacking data volume is obtained by stacking multiple sub-gathers. This partial stacking data volume is used to obtain the target incident angle range with good amplitude fidelity for each marker reflection layer. Since the relative relationship of amplitude attributes across the entire work area is considered, the correlation between actual drilled wells is enhanced. This makes the trend of reflection amplitude variation with incident angle closer to the forward modeling results of well data, improving the reliability of AVO intercept, reducing the error between the intercept of the fitting equation and the actual situation, improving the compensation effect of fidelity amplitude compensation, and making the matching degree of well-seismic data higher and the amplitude fidelity better. This solves the problem in the existing technology where the intercept of the fitting equation differs greatly from the actual situation, resulting in poor compensation effect of fidelity amplitude compensation.

[0017] Furthermore, in order to better obtain the target incident angle range, the present invention provides an amplitude compensation method for seismic CRP gathers oriented to pre-stack inversion, which further includes the step of determining the target incident angle range in step 3) as follows: extracting the root mean square amplitude attribute distribution statistics of each part of the stacked data volume along each marker reflection layer; judging the amplitude fidelity at different plane positions based on the amplitude attribute distribution statistics results of each part of the stacked data volume, and taking the incident angle range with better amplitude fidelity as the target incident angle range.

[0018] Furthermore, in order to better obtain the superimposed data volume, the present invention provides an amplitude compensation method for seismic CRP gathers oriented to pre-stack inversion, which also includes, in step 3), dividing the sub-gathers into equal parts according to the incident angle range.

[0019] Furthermore, to better perform amplitude compensation, this invention provides an amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion, which also includes the process of determining the effective incident angle range in step 2): For the top or bottom marker reflection layer in the well-side CRP gather, determine the incident angle range within the work area that conforms to the response characteristics of the actual drilled well AVO forward modeling gather on the marker reflection layer; the minimum incident angle in each incident angle range forms the minimum incident angle set, and the maximum incident angle in each incident angle range forms the maximum incident angle set; select the maximum incident angle in the minimum incident angle set as the lower limit of the effective incident angle range of the marker reflection layer, and select the minimum incident angle in the maximum incident angle set as the upper limit of the effective incident angle range of the marker reflection layer, thereby obtaining the effective incident angle ranges of the top and bottom marker reflection layers.

[0020] Furthermore, in order to obtain the compensation coefficient better, the present invention provides an amplitude compensation method for seismic CRP gathers oriented to pre-stack inversion, which further includes linear interpolation in step 6).

[0021] Furthermore, in order to achieve better amplitude compensation, this invention provides an amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion, which also includes a target segment compensation coefficient body as follows:

[0022]

[0023] Where i is the seismic CRP gather number, t is the reflection time corresponding to the amplitude compensation coefficient, θ is the incident angle of the reflected wave, t1 is the reflection time of the top marker reflection layer of the target segment, and k i,θ t2 is the compensation coefficient of the top marker reflector layer, t2 is the reflection time of the bottom marker reflector layer of the target segment, and k′ is the reflection time of the bottom marker reflector layer of the target segment. i,θ This is the compensation coefficient for the bottom marker reflective layer.

[0024] Furthermore, in order to obtain the values ​​of each parameter in the AVO fitting equation more accurately, this invention provides an amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion, which also includes the least squares fitting method used in steps 2) and 3).

[0025] Furthermore, to intuitively reflect the influence of each parameter on the reflection coefficient, this invention provides an amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion, and also includes a simplified equation for the AVO fitting equation using the Zoeppritz equation, the simplified equation being:

[0026] R = A + B sin 2 θ

[0027] Where R is the longitudinal wave reflection coefficient, A is the intercept, and B is the gradient.

[0028] The present invention also provides an amplitude compensation system for pre-stack inverted seismic CRP gathers, comprising a memory and a processor, wherein the processor is used to execute instructions stored in the memory to implement the above-described amplitude compensation method for pre-stack inverted seismic CRP gathers. Attached Figure Description

[0029] Figure 1 This is a flowchart of the amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion according to the present invention;

[0030] Figure 2(a) shows Well 01 A schematic diagram of the AVO orthogonal progression of the well;

[0031] Figure 2(b) shows Well 02 A schematic diagram of the AVO orthogonal progression of the well;

[0032] Figure 2(c) shows Well 01 Well 02 AVO analysis diagram of the bottom marker reflector layer of the target well section;

[0033] Figure 3 For Well 01 AVO analysis quality control chart of the marker reflective layer at the bottom of the well;

[0034] Figure 4(a) shows the root mean square amplitude attribute extracted along the bottom marker reflective layer;

[0035] Figure 4(b) shows the passage through Well 01 Quality control analysis diagram of superimposed profile of well injection angle;

[0036] Figure 5 For actual drilling Well 01 A schematic diagram comparing the AVO curves of the bottom marker reflection layer before and after amplitude compensation using different methods in wells;

[0037] Figure 6 For actual drilling Well 02 A schematic diagram comparing the AVO curves of the bottom marker reflection layer before and after amplitude compensation using different methods. Detailed Implementation

[0038] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example of amplitude compensation method for seismic CRP gathers for pre-stack inversion:

[0040] Figure 1 This is a flowchart of the amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion according to the present invention. The specific process is as follows:

[0041] Step 1: Acquire seismic and well logging data, generate AVO forward modeling gathers from actual drilled wells based on the acquired well logging data, and determine the top and bottom marker reflection layers of the target section.

[0042] Specifically, such as Figure 1 As shown, basic data collection was conducted to acquire seismic and well logging data from the basic data. The collected basic data included key well logging data, as well as seismic CRP gathers and stacked data volumes within the work area. Key well logging data included P-wave velocity curves, S-wave velocity curves, and density curves. The work area included multiple drilled wells, and corresponding AVO forward modeling gathers for these drilled wells were generated using the data from these drilled wells in the basic data.

[0043] In step one, since the marker reflection layers are continuously traceable and easily identifiable across the entire seismic stacking data volume (e.g., uniform overall thickness, uniform lithology, similar amplitude values, and relatively stable rock strata properties), these characteristics are used to determine the top and bottom marker reflection layers of the target segment. The strata between the top and bottom marker reflection layers are defined as the target segment for amplitude compensation.

[0044] For the purposes of this embodiment, to facilitate the demonstration of the technical effect of the amplitude compensation method in conjunction with the accompanying drawings, this embodiment uses 3D seismic gather data from a tight sandstone gas exploration area in northeastern Sichuan as an example. The key terrestrial reservoir in this area is a tight sandstone reservoir in the first member of the Middle Jurassic Qianfoya Formation. There are two drilled wells in the area. After quality control analysis, it was found that the amplitude fidelity of the original CRP gather in this area was poor. Basic data for this area were collected and statistically analyzed. The collected basic data includes data from the two drilled wells. 01 Well 02 The longitudinal wave velocity curve v P1 v P2 Shear wave velocity curve v S1 v S2 The medium density curves ρ1 and ρ2, as well as seismic CRP gather data and stacked data volumes, were obtained. Through stacked data volume gather and profile quality control, the bottom boundary reflection layer (TJ2q) of the Middle Jurassic Qianfoya Formation II was found in the study area. 2 ) and the bottom boundary reflective layer of the Qianfoya Formation (TJ2q) 1 The wave exhibits medium to strong amplitude peak reflection characteristics with good continuity, allowing for effective and continuous tracking throughout the area. Furthermore, the tight sandstone reservoir is located between the two reflection interfaces. Therefore, the first section of the Qianfoya Formation was designated as the target section for amplitude compensation, and the reflecting layer TJ2q was selected. 2 Designated as the top marker reflective layer, reflective layer TJ2q 1 Designated as the bottom marker reflector layer. Utilizing two actual drilled wells (Well... 01 Well 02The data is used to generate the corresponding AVO forward modeling gathers for actual drilling wells, for example, to obtain the Well shown in Figure 2(a). 01 A schematic diagram of the bottom marker reflective layer of the AVO forward set and Figure 2(b) showing the Well. 02 Schematic diagram of the bottom marker reflective layer of the AVO forward set.

[0045] In step one, as Figure 1 As shown, this also includes AVO analysis of the identified top and bottom marker reflection layers. Specifically, since P-wave sources are dominant in seismic exploration, and although the Zoeppritz equation can fully reflect the energy distribution of various converted waves on both sides of the interface, its calculation process is too complex and difficult to solve. In order to reduce the amount of calculation and the impact of unnecessary parameters on AVO forward modeling, and to reflect the influence of various media elastic parameters on the reflection coefficient more intuitively in seismic inversion work, simplified equations of the Zoeppritz equation are often used to obtain the AVO fitting equation in actual AVO analysis. The simplified equation forms used include: the two-term Shuey simplified equation: R = A + Bsin 2 θ and the simplified equation of the trinomial Shuey: R = A + B sin 2 θ+C*tan 2 θ*sin 2 θ, where θ is the incident angle of the reflected wave, t is the time value indicating the location of the reflective layer, R is the P-wave reflection coefficient, A is the AVO intercept (or simply intercept), reflecting the P-wave reflection coefficient under zero incident angle conditions, B is the AVO gradient (or simply gradient), and C is the AVO curvature. When θ = 0–30°, tan 2 θ*sin 2 When θ approaches 0, the third term has almost no effect on the reflection coefficient. However, when θ > 30°, the effect of the third term on the reflection coefficient becomes significant. Considering that the incident angle of the effective reflection phase axis in most CRP gather data does not exceed 30°, this embodiment uses the two-term Shuey simplified equation as the simplified equation commonly used in obtaining the AVO fitting equation.

[0046] In step one, the response characteristics of the top and bottom marker reflective layers are obtained through AVO analysis. For example, the Well markers shown in Figures 2(a) and 2(b) are analyzed. 01 Well 02 AVO analysis of the marker reflector layer at the bottom of the target well section yielded the Well shown in Figure 2(c). 01 Well 02Based on Figure 2(c), the AVO response curves of the bottom marker reflector layer in the target well section show that the reflection amplitude of the bottom marker reflector layer in both drilled wells decreases with increasing incident angle. This indicates that the AVO response type characteristics (i.e., response characteristics) of the bottom marker reflector layers in the two drilled wells are consistent. Based on Figure 2(c), the simplified bipartite Shuey equations for the two drilled wells are obtained. 01 Well 02 The full-offset AVO approximation equations for the bottom marker reflector layer of the well AVO forward modeling gather are as follows:

[0047] R Well01 =23221.0371-84349.3828 sin 2 θ

[0048] R Well02 =24217.5831-87147.7344 sin 2 θ

[0049] Where θ is the incident angle of the reflected wave, R Well01 and R Well02 This represents the longitudinal wave reflection coefficient at an incident angle of θ.

[0050] Step 2: Determine the effective incident angle range, and use the seismic data within the effective incident angle range to fit the gradient in the AVO fitting equation for the top and bottom marker reflector layers.

[0051] In step two, as Figure 1 As shown, the effective incident angle range α of the AVO gradient is obtained by using the AVO forward modeling gather from actual drilled wells to identify the top marker reflector layer of the target section in the actual seismic CRP gather. min ~α max The effective incident angle range α′ of the AVO gradient is obtained by calculating the bottom marker reflective layer. min ~α′ max Specifically, the AVO response characteristics of the top and bottom marker reflectors of the target segment are compared between the actual well AVO forward model gather and the well-side CRP gather. The effective incident angle range of the top and bottom marker reflectors of the well-side CRP gather (i.e., the actual CRP gather) is determined. Within the effective incident angle range, the reflection amplitude in the seismic data decreases as the incident angle increases. The gradients in the AVO fitting equations for the top and bottom marker reflectors are obtained by fitting the seismic data within the effective incident angle range.

[0052] In step two, determining the effective incident angle range of the top and bottom marker reflection layers of the CRP gathers near the drilled wells, which conform to the response characteristics of the AVO forward modeling gathers of the drilled wells, involves comparing the effective incident angle ranges of all CRP gathers near the wells within the work area to obtain the effective incident angle ranges of each marker reflection layer for all seismic CRP gathers in the work area. This includes: for the top or bottom marker reflection layers in the CRP gathers near the wells, determining the incident angle range of all drilled wells within the work area that conforms to the response characteristics of the AVO forward modeling gathers of the drilled wells on that marker reflection layer; the minimum incident angle in each incident angle range forms the minimum incident angle set, and the maximum incident angle in each incident angle range forms the maximum incident angle set; the maximum incident angle in the minimum incident angle set is selected as the lower limit of the effective incident angle range of that marker reflection layer, and the minimum incident angle in the maximum incident angle set is selected as the upper limit of the effective incident angle range of that marker reflection layer, thus obtaining the effective incident angle ranges of the top and bottom marker reflection layers. This allows for better amplitude compensation. For example, for the top marker reflection layer of the seismic CRP gather, the range of incident angles on the marker reflection layer of all actual drilled wells (e.g., N actual drilled wells) in the work area is first obtained, which conform to the AVO response type characteristics of the forward modeling gathers of actual drilled wells. The minimum incident angle in each incident angle range forms the minimum incident angle set (α). min1 α min2 , …, α minN The maximum incident angles within each incident angle range constitute the maximum incident angle set (α). max1 α max2 , …, α maxN ), α min1 α min2 , …, α minN The maximum incident angle is defined as α. min , α max1 α max2 , …, α maxN The minimum incident angle is defined as α. max This allows us to obtain the effective incident angle range α of the marker reflector that satisfies the AVO response type characteristics of all seismic CRP gathers within the work area. min ~α max Using the same method, the effective incident angle range α′ of the bottom marker reflector layer that meets the AVO response type characteristics of forward-modeled gathers for all seismic CRP gathers within the work area can be obtained. min ~α′ max The seismic CRP gathers include well-side CRP gathers and distant-well CRP gathers. Therefore, an effective incident angle range can be extracted from the forward modeling gathers of a single well and the well-side CRP gathers, and then a multi-well comparison can be used to determine an effective incident angle range applicable to the seismic CRP gathers across the entire work area.

[0053] Figure 3 For Well01 AVO analysis quality control chart of the marker reflector layer at the bottom of the well. For this embodiment, using Well... 01 Well 02 Taking a well as an example, the bottom marker reflector layer TJ2q of the target section in the CRP gather and AVO forward modeling gather near the actual drilled well is analyzed. 1 Perform AVO analysis and compare Figure 3 Well 01 From the well-side CRP gather bottom marker reflection layer seismic data points and the AVO forward modeling gather bottom marker reflection layer AVO response curve, it can be seen that the actual drilled well... 01 Within the incident angle range of 0° to 5°, the reflection amplitude of the CRP gather near the well significantly increases with increasing incident angle, contrary to the characteristics of the AVO response curve exhibited by the AVO forward modeling gather. However, within the incident angle range greater than 26°, the reflection amplitude shows more negative values ​​and exhibits a generally slow increasing trend (e.g., ...). Figure 3 As shown), therefore, the effective incident angle range of the marker reflective layer at the bottom of the CRP gather next to the well is 5° to 26°, which conforms to the forward modeling AVO response characteristics; similarly, comparing with Well... 02 The well-drilled well was obtained by using seismic data points from the bottom marker reflector layer of the CRP gather near the well and the AVO response curve of the bottom marker reflector layer of the AVO forward modeling gather. 02 The effective incident angle range of the bottom marker reflector layer of the target section obtained from the CRP traces near the well is 4° to 27°, which conforms to the forward modeling AVO response characteristics. Therefore, the effective incident angle range for obtaining the AVO gradient of the bottom marker reflector layer from the actual seismic CRP traces is determined to be 5° to 26°. Using the same method, the effective incident angle range for obtaining the AVO gradient of the top marker reflector layer from the actual seismic CRP traces is determined to be 4° to 25°.

[0054] In step two, after obtaining the effective incident angle range of the top and bottom marker reflectors in the seismic CRP gathers, the gradient B in the AVO fitting equation for each top and bottom marker reflector in each seismic CRP gather is obtained by fitting the seismic data within this effective incident angle range. For example, using seismic data of the bottom marker reflector within the effective incident angle range of 5° to 26° in the seismic CRP gathers, the bottom marker reflector TJ2q in all actual seismic CRP gathers is derived using the least squares fitting method with the simplified bipartite Shuey equation. 1 The AVO fitting equation, where the actual drilled well Well 01 The fitting equation for the AVO of the bottom marker reflective layer of the CRP channel near the well is as follows:

[0055] R Well01 =25354.1571-83942.3538 sin 2 θ

[0056] Well drilling 02 The fitting equation for the AVO of the bottom marker reflective layer of the CRP channel near the well is as follows:

[0057] R Well02 =24767.4961-87276.8951 sin 2 θ

[0058] R Well01 and R Well02 To determine the P-wave reflection coefficients for different drilled wells at an incident angle of θ, a comparison of the AVO equations for the bottom marker reflection layer in the AVO forward modeling gathers of the drilled wells and the CRP gathers near the well reveals that the AVO gradient values ​​are similar, indicating a good match between the well-seismic data and the P-wave reflection coefficients. 01 The AVO intercept obtained from the wellside CRP gather fitting differs significantly from the AVO analysis results in the actual well forward modeling gather. Therefore, to avoid the overall value of the seismic reflection amplitude of the bottom marker reflection layer of the wellside CRP gather being larger than the theoretical value within the incident angle of 5° to 26°, a new intercept of the AVO fitting equation is obtained using step three.

[0059] Step 3: Determine the target incident angle range, use the gradient in the fitted AVO equation as a known quantity, and use the seismic data within the target incident angle range to obtain the target AVO fitting equation for each marker reflection layer.

[0060] Specifically, in step three, the seismic CRP gather is first divided into multiple sub-gathers according to the range of reflected wave incident angles. These sub-gathers are then stacked to obtain corresponding partial stacked data volumes. This allows for the statistical analysis of the amplitude of all seismic CRP gathers, enabling the assessment of the fidelity of their relative relationships. Next, comparative analysis of the various stacked data volumes determines the target incident angle ranges with good amplitude fidelity for the top and bottom marker reflectors. Then, using the gradient in the fitted AVO equation as a known quantity, the least squares fitting method is applied to the seismic data of all seismic CRP gathers within the target incident angle range to obtain the intercepts A in the AVO fitting equations for the top and bottom marker reflectors. Finally, based on the fitted gradient B and intercept A, the target AVO fitting equations (i.e., the complete AVO fitting equations) for the top and bottom marker reflectors of the actual seismic CRP gathers are obtained. Thus, the target AVO fitting equations for each seismic CRP gather can be obtained.

[0061] In step three, such as Figure 1As shown, the steps for determining the target incident angle range with good amplitude fidelity for the top and bottom marker reflective layers by comparing and analyzing the superimposed data volumes of each part include: extracting the root mean square amplitude attribute along the top or bottom marker reflective layer for each part of the superimposed data volume; judging whether the relative amplitude relationship at different planar positions is reliable based on the statistical results of the amplitude attribute distribution of each part of the superimposed data volume (i.e., the planar distribution statistical results); and taking the incident angle range with reliable relative amplitude relationship as the target incident angle range with good amplitude fidelity. The target incident angle range of the top marker reflective layer is represented by β. min ~β max The target incident angle range of the bottom marker reflective layer is indicated by β′. min ~β′ max This indicates that the incident angle range with relatively reliable fidelity in preserving the relative relationships of amplitude attributes at different spatial locations across the entire work area can be obtained.

[0062] For this embodiment, Figure 4(a) is the root mean square amplitude attribute map extracted along the bottom marker reflective layer; Figure 4(b) is the over-Well... 01 Quality control analysis diagram of the stacked profile with incident angles. Since the incident angle range of the effective reflection phase axis in the target layer of the actual seismic CRP gather is 0° to 30°, if the actual seismic CRP gather is divided into 5 sub-gathers, each sub-gathering represents a sub-incident angle range of 6°, and then the sub-gathers are stacked separately, the 5 sub-incident angle range partial stacked data volumes are obtained. For example, the root mean square amplitude attribute of each part of the stacked data volume is extracted along the bottom marker reflection layer to obtain the root mean square amplitude attribute map of each part of the stacked data volume shown in Figure 4(a). In Figure 4(a), from left to right, are the root mean square amplitude attribute maps of the partial stacked data volumes with incident angle ranges of 0° to 6°, 6° to 12°, 12° to 18°, 18° to 24°, and 24° to 30°. Based on the root mean square amplitude attribute map of each part of the superimposed data volume, the superimposed profile quality control analysis map shown in Figure 4(b) shows that the relative amplitude relationship of the root mean square amplitude attribute at different plane positions is well preserved within the incident angle range of 6° to 18°, the continuity of the same axis is good, and it is relatively stable. Therefore, the target incident angle range of the AVO intercept of the bottom marker reflection layer in the actual earthquake CRP concentrator is set to 6° to 18°.

[0063] Using seismic data from individual seismic traces within the work area, covering the bottom marker reflector layer of each actual CRP seismic trace within an incident angle range of 6°–18°, the TJ2q bottom marker reflector layer of the actual CRP seismic traces was derived using the least squares fitting method. 1 The intercept A in the AVO fitting equation i Thus, the complete AVO fitting equation for the bottom marker reflector layer of each actual earthquake CRP gather is obtained: R′ i,θ =A′i -B′ i *sin 2 θ, by analogy with this method, can be used to obtain the complete AVO fitting equation for the top marker reflector layer in actual seismic CRP gathers: R i,θ =A i -B i *sin 2 θ, where R i,θ A represents the longitudinal wave reflection coefficient of the top marker reflector layer. i B is the intercept of the top marker reflective layer. i Let R′ be the gradient of the top marker reflection layer. i,θ Let A′ be the longitudinal wave reflection coefficient of the top marker reflector layer. i B′ is the intercept of the top marker reflective layer. i The gradient of the top marker reflector layer is denoted by , and i is the CRP number of the earthquake CRP gather.

[0064] Using actual drilling Well 01 For seismic data within the incident angle range of 6° to 18° of the bottom marker reflector layer in actual seismic CRP gathers, a new intercept is obtained using the least squares fitting method. Based on the new intercept and the gradient obtained in step two, the actual wellbore data can be obtained. 01 The complete AVO fitting equation for the bottom marker reflector layer of the CRP channel near the well is as follows:

[0065] R Well01 =23268.2486-83942.3538 sin 2 θ

[0066] Using actual drilling Well 02 For seismic data within the incident angle range of 6° to 18° of the bottom marker reflector layer in actual seismic CRP gathers, a new intercept is obtained using the least squares fitting method. Based on the new intercept and the gradient obtained in step two, the actual wellbore data can be obtained. 02 The fitting equation for the AVO of the bottom marker reflective layer of the CRP channel near the well is as follows:

[0067] R Well02 =24352.1157-87276.8951 sin 2 θ

[0068] Comparison shows that using the statistical results of the root mean square amplitude attributes extracted along the bottom marker reflection layer to constrain the AVO intercept in the AVO fitting equation yields an AVO intercept value in the actual seismic CRP gather that is closer to the result obtained from the forward modeling of actual drilled wells, indicating a better match between well and seismic data. This reduces the overall deviation between the seismic reflection amplitude of the bottom marker reflection layer in the seismic CRP gather and the theoretical value, improving the amplitude fidelity of the compensation results.

[0069] Step 4: Based on the target AVO fitting equations of the top and bottom marker reflector layers, obtain the theoretical amplitude values ​​of the corresponding seismic traces in the top and bottom marker reflector layers. Use the theoretical amplitude values ​​and the actual amplitude values ​​of the corresponding seismic traces to obtain the amplitude compensation coefficients of the top and bottom marker reflector layers.

[0070] Specifically, in step four, the theoretical amplitude value R of each seismic trace in the top marker reflection layer of each actual seismic CRP gather is obtained by using the target AVO fitting equation of the top marker reflection layer of the target segment obtained in step three. i,θ And obtain the actual amplitude value r corresponding to each seismic trace of the top marker reflector layer. i,θ The theoretical amplitude value R on each seismic trace i,θ Compared with the actual amplitude value r i,θ The ratio is defined as the compensation coefficient k of that path on the top marker reflective layer. i,θ , i.e., k i,θ =R i,θ / r i,θ Using this formula for derivation, the compensation coefficient attribute body K, which includes the amplitude compensation coefficients of the top marker reflector layer in all actual earthquake CRP traces, can be obtained. i,θ Refer to the compensation coefficient attribute K corresponding to the top marker reflection layer. i,θ The method yields the compensation coefficient attribute volume K′ corresponding to the bottom marker reflection layer. i,θ Where i represents the CRP index of the seismic CRP gather, and θ is the angle of incidence.

[0071] In this embodiment, the target AVO fitting equation of the bottom marker reflector layer of the target segment obtained in step three is used to obtain the actual drilled well. 01 The theoretical reflection amplitude (i.e., theoretical amplitude value) of the seismic trace with θ = 20° at the bottom marker reflector layer of the well is approximately 13458.40, corresponding to an actual amplitude value of 15642.31. Therefore, the compensation coefficient of the bottom marker reflector layer on this seismic trace is approximately 0.8604. Similarly, the compensation coefficient of the top marker reflector layer on the same seismic trace is approximately 1.0688.

[0072] Step 5: Perform linear interpolation on the amplitude compensation coefficients corresponding to the top and bottom marker reflection layers to obtain the compensation coefficient volume of the target layer, and then obtain the compensated seismic CRP gather.

[0073] In step five, as Figure 1 As shown, the compensation coefficient K of the reflective layer at the top and bottom of the target layer is marked. i,θ and K′ i,θ Linear interpolation is performed along the vertical direction to obtain the compensation coefficient volume K for the target segment. final The final seismic CRP gather data volume was obtained after application. Therefore, by using two marker reflection layers (top and bottom marker reflection layers at different vertical locations) to calculate the amplitude compensation coefficient, the fidelity of the amplitude compensation results at the reservoir location was improved.

[0074] Specifically, the amplitude compensation coefficient at different times within the target segment is calculated using a linear interpolation method based on the vertical sampling interval of the seismic data. The compensation coefficient body for the target segment is then as follows:

[0075]

[0076] Among them, K i,θ,t Let t1 be the amplitude compensation coefficient at time t within the target layer of the seismic CRP gather with incident angle θ, where i is the seismic CRP gather number, t is the reflection time corresponding to the amplitude compensation coefficient, θ is the incident angle of the reflected wave (abbreviated as incident angle), t1 is the reflection time of the top marker reflector layer of the target layer, and k is the amplitude compensation coefficient at time t. i,θ t1 is the compensation coefficient of the top marker reflector layer (i.e., the amplitude compensation coefficient at time t1), t2 is the reflection time of the bottom marker reflector layer of the target segment, and k′ is the reflection time of the bottom marker reflector layer of the target segment. i,θ This is the compensation coefficient for the bottom marker reflective layer (i.e., the amplitude compensation coefficient at time t2). The target layer compensation coefficient is K. i,θ,t After application, the final seismic CRP gather data volume can be obtained. This allows for better amplitude compensation.

[0077] For the purposes of this embodiment, Figure 5 For actual drilling Well 01 A schematic diagram comparing the AVO curves of the bottom marker reflective layer before and after amplitude compensation using different methods; Figure 6 For actual drilling Well 02 A schematic diagram comparing the AVO curves of the bottom marker reflection layer before and after amplitude compensation using different methods. Specifically, when using the "planar statistical method" for amplitude compensation, Well... 01 The amplitude compensation factor for the wellbore CRP gather is 0.8748. 02 The amplitude compensation coefficient for the well-side CRP gather is 0.9553. The effective incident angle range of the "well-controlled offset extrapolation method" is the same as the effective incident angle range of the method used in this invention.

[0078] Experiments have shown that actual drilling... 01 The reflection time corresponding to the bottom marker reflection layer of the seismic trace with a concentrated incident angle of 20° near the well is 1603 ms, with a compensation coefficient of approximately 0.8604. The reflection time corresponding to the top marker reflection layer is 1560 ms, with a compensation coefficient of approximately 1.0688. Therefore, the compensation coefficients corresponding to each seismic data sample point within the target layer of this seismic trace are:

[0079]

[0080] That is, k Well01,20,t =1.0688-0.00215(t-1560).

[0081] based on Figure 5 and Figure 6 The actual drilled well shown 01 Well 02 The results of AVO analysis of the bottom marker reflector layer of the target formation before and after concentrated compensation of the CRP channel near the well, and the actual drilled wells shown in Tables 1 and 2. 01 Wells and actual drilled wells 02 The reflection amplitude values ​​of the bottom marker reflection layer at each incident angle before and after amplitude compensation using different methods are compared. It can be seen that after amplitude compensation using the "plane statistical method," the overall energy level of the CRP gather is reasonably corrected, but there is undercompensation in seismic traces with larger reflection amplitudes at small incident angles and overcompensation in seismic traces with smaller reflection amplitudes at large incident angles. Furthermore, the AVO gradient of the bottom marker reflection layer still shows significant anomalies. After amplitude compensation using the "well-controlled offset extrapolation method," the AVO gradient of the bottom marker reflection layer of the CRP gather is reasonably corrected, but the AVO intercept is inaccurate. 01 Well 02 The relative amplitude relationships between well-side CRP gathers are not preserved, which is detrimental to pre-stack inversion. Compared with existing CRP gather amplitude compensation methods, the method in this embodiment not only makes the reflection amplitude variation with incident angle closer to the forward modeling results of well data, but also makes the AVO intercept more reliable, the well-seismic data matching degree higher, and the amplitude fidelity better, which can meet the needs of subsequent pre-stack inversion, reservoir prediction, and quantitative reservoir description.

[0082] Table 1. Actual Drilled Wells 01 Reflection amplitude values ​​of each incident angle of the bottom marker reflection layer before and after amplitude compensation using different methods

[0083]

[0084] Table 2 Actual Drilled Wells 02 Reflection amplitude values ​​of each incident angle of the bottom marker reflection layer before and after amplitude compensation using different methods

[0085]

[0086] According to the amplitude compensation method of the present invention, firstly, by comparing the forward modeling results of a single well with the CRP gather near the well, the effective incident angle range of the reliable AVO gradient of the CRP gather near the well is determined. Then, by comparing the effective incident angle range of all CRP gathers near the well in the work area, the effective incident angle range of each marker reflection layer of all seismic CRP gathers in the work area is obtained. Then, the AVO fitting equation of each marker reflection layer on each seismic CRP gather is obtained. In this case, it is assumed that the amplitude data of CRP gathers in the work area, including those in the far-well area, also have good fidelity within this incident angle range. Thus, reliable data obtained by multi-well constraints are used for fitting to obtain the corresponding AVO fitting equation, so that the AVO gradient parameters of each seismic CRP gather can be obtained for their respective locations, thereby avoiding the problem of unreasonable interpolation. In addition, the amplitude compensation coefficient is calculated using the top and bottom marker reflection layers, which can improve the fidelity of the amplitude compensation results at the reservoir location. Furthermore, based on the seismic CRP gathers divided into multiple sub-gathers according to the range of incident angles of reflected waves, a partial stacking data volume is obtained by stacking multiple sub-gathers. This partial stacking data volume is used to obtain the target incident angle range with good amplitude fidelity for each marker reflection layer. Since the relative relationship of amplitude attributes across the entire work area is considered, the correlation between actual drilled wells is enhanced. This makes the trend of reflection amplitude variation with incident angle closer to the forward modeling results of well data, improving the reliability of AVO intercept, reducing the error between the intercept of the fitted equation and the actual situation, and enhancing the compensation effect of fidelity amplitude compensation. It also makes the matching degree of well-seismic data higher and the amplitude fidelity better, effectively solving the problem in the existing technology where the intercept of the fitted equation differs greatly from the actual situation, resulting in poor compensation effect of fidelity amplitude compensation. The compensation method in this embodiment uses multiple wells to perform amplitude compensation on the CRP gathers of the entire work area during the amplitude compensation coefficient calculation process. This method is highly practical and comprehensively considers the influence of three factors on the reflection amplitude compensation coefficient: incident angle, lateral non-homogeneity of the subsurface medium, and vertical distance from the marker reflector layer. This results in a reasonable amplitude compensation coefficient, improving the amplitude fidelity of the seismic CRP gathers and laying a data foundation for pre-stack inversion. Furthermore, it better reflects the actual propagation process of seismic reflected waves. By using more constraints to enhance the rationality of the amplitude compensation coefficient, it helps improve the fidelity of the amplitude compensation results, thereby strengthening the practicality of the fidelity amplitude compensation method and contributing to improving the reliability of fidelity amplitude compensation results for seismic CRP gathers in sparsely populated areas.

[0087] Example of an amplitude compensation system for seismic CRP gathers for pre-stack inversion:

[0088] This embodiment discloses an amplitude compensation system for pre-stack inverted seismic CRP gathers. Through this amplitude compensation system for pre-stack inverted seismic CRP gathers, the amplitude compensation method for pre-stack inverted seismic CRP gathers described in the method embodiments of this invention can be implemented.

[0089] In this embodiment, the amplitude compensation system for pre-stack inverted seismic CRP gathers includes a processor and a memory. The processor executes instructions stored in the memory to implement the amplitude compensation method for pre-stack inverted seismic CRP gathers in this method embodiment. This amplitude compensation method for pre-stack inverted seismic CRP gathers has been described in detail in the above method embodiments. Those skilled in the art can generate corresponding computer instructions based on this amplitude compensation method to obtain the amplitude compensation system for pre-stack inverted seismic CRP gathers; further details are omitted here. The memory stores the computer instructions generated according to the amplitude compensation method for pre-stack inverted seismic CRP gathers.

[0090] The amplitude compensation system for seismic CRP gathers oriented to pre-stack inversion in this embodiment can effectively solve the problem that existing technologies often have poor compensation effects due to a large discrepancy between the intercept of the fitted equation and the actual situation.

Claims

1. An amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion, characterized in that, include: 1) Acquire seismic and well logging data, generate AVO forward modeling gathers of actual drilled wells based on the acquired well logging data, and determine the top and bottom marker reflection layers of the target interval; 2) Compare the AVO response characteristics of each marker reflection layer in the actual well AVO forward model gather and the well-side CRP gather respectively, determine the effective incident angle range of each marker reflection layer in the well-side CRP gather that conforms to the response characteristics of the actual well AVO forward model gather, and obtain the effective incident angle range of each marker reflection layer in all seismic CRP gathers in the work area by comparing the effective incident angle range of all well-side CRP gathers in the work area. Based on the seismic data within this effective incident angle range, the gradient in the AVO fitting equation of each marker reflection layer on each seismic CRP gather is obtained. 3) Divide the seismic CRP gather into multiple sub-gathers according to the range of incident angles of reflected waves, and stack them to obtain corresponding partial stacked data volumes. Compare and analyze the various stacked data volumes to determine the range of target incident angles with good amplitude fidelity on the top and bottom marker reflector layers. 4) Using the gradient in the AVO fitting equation obtained in step 2) as a known quantity, the intercept in the AVO fitting equation of each marker reflection layer on the seismic CRP gather is obtained by fitting the seismic data within the target incident angle range. 5) Based on the gradient obtained from step 2) and the intercept obtained from step 4), determine the target AVO fitting equation for each marker reflection layer on the seismic CRP gather. Based on the target AVO fitting equation for each marker reflection layer, obtain the theoretical amplitude value of the corresponding seismic trace in each marker reflection layer. Use the theoretical amplitude value and the actual amplitude value of the corresponding seismic trace to obtain the amplitude compensation coefficient corresponding to each marker reflection layer. 6) Interpolate the amplitude compensation coefficients corresponding to each marker reflection layer to obtain the compensation coefficient volume of the target segment, and then obtain the compensated seismic CRP gather.

2. The amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion according to claim 1, characterized in that, In step 3), the steps for determining the target incident angle range include: extracting the root mean square amplitude attribute distribution statistics of each part of the superimposed data volume along each marker reflection layer; judging the amplitude fidelity at different plane positions based on the amplitude attribute distribution statistics of each part of the superimposed data volume; and taking the incident angle range with better amplitude fidelity as the target incident angle range.

3. The amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion according to claim 1, characterized in that, In step 3), the sub-sets are divided equally according to the range of incident angles.

4. The amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion according to claim 1, characterized in that, In step 2), the process of determining the effective incident angle range is as follows: For the top or bottom marker reflection layer of the CRP gather near the well, determine the incident angle range within the work area that conforms to the response characteristics of the AVO forward modeling gather of the actual drilled well on the marker reflection layer; the minimum incident angle in each incident angle range forms the minimum incident angle set, and the maximum incident angle in each incident angle range forms the maximum incident angle set. Select the maximum incident angle in the minimum incident angle set as the lower limit of the effective incident angle range of the marker reflection layer, and select the minimum incident angle in the maximum incident angle set as the upper limit of the effective incident angle range of the marker reflection layer, thereby obtaining the effective incident angle range of the top and bottom marker reflection layers.

5. The amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion according to claim 1, characterized in that, In step 6), the interpolation method is linear interpolation.

6. The amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion according to claim 1 or 5, characterized in that, The target segment compensation coefficient is as follows: Where i is the seismic CRP gather number, The reflection time corresponds to the amplitude compensation coefficient. The incident angle of the reflected wave. The reflection time of the top of the target layer is marked by the reflective layer. The compensation coefficient for the top marker reflective layer. The reflection time of the bottom marker reflector of the target segment. This is the compensation coefficient for the bottom marker reflective layer.

7. The amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion according to claim 1, characterized in that, In steps 2) and 3), the fitting method is the least squares fitting method.

8. The amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion according to claim 1 or 7, characterized in that, The AVO fitting equation uses a simplified version of the Zoeppritz equation, which is: in, For longitudinal wave reflection coefficient, The intercept is... For gradient.

9. An amplitude compensation system for seismic CRP gathers oriented towards pre-stack inversion, characterized in that, include: A memory and a processor, the processor being configured to execute instructions stored in the memory to implement the amplitude compensation method for seismic CRP gathers oriented towards pre-stack inversion as described in any one of claims 1-8.

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