Establishment method of plastic formation velocity model, electronic equipment and storage medium

Abstract

The invention belongs to the technical field of geophysical exploration, and particularly discloses a method for establishing a plastic formation velocity model, electronic equipment and a computer readable storage medium. The method comprises the following steps: firstly, establishing a final plastic formation overburden velocity model, finely picking up the top layer and the bottom layer of the plastic formation, filling the velocity of the plastic formation according to logging information, and establishing an initial velocity model of the plastic formation; updating the initial speed model of the plastic formation according to a variable speed model operator and an omnibearing grid chromatography technology to obtain a final speed model of the plastic formation; the model is fused and spliced with a final plastic stratum overburden velocity model; and finally, on the basis of the fused and spliced velocity model, establishing a velocity model of the underlying formation of the plastic formation according to drilling and logging information, and updating and iterating to obtain a final velocity model. The method is used for depicting the ultra-deep heterogeneous reservoir, the multiplicity of solution of lithology inner screen imaging is effectively reduced, and finer and more reliable depicting of the ultra-deep heterogeneous reservoir is achieved.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration technology, specifically relating to a method for establishing a plastic formation velocity model, an electronic device, and a storage medium. Background Technology

[0002] Carbonate reservoirs, due to their deep burial depths (generally 6000-7500 meters), exhibit rapid seismic signal attenuation, strong lateral heterogeneity, and complex gas-water relationships. In particular, the overlying Triassic strata widely develop a set of plastic gypsum-crumpled formations with abrupt changes in thickness and velocity both longitudinally and laterally, resulting in severe longitudinal and lateral distortions in the travel times of pre-stack migrations of deep carbonate strata. Under current limitations in velocity iteration accuracy, it is impossible to accurately characterize the velocity structure changes of plastic strata, affecting the imaging accuracy of deep carbonate targets. Based on geological requirements, the core focus of processing deep heterogeneous carbonate reservoirs is to achieve high-fidelity, high-resolution imaging of heterogeneous structures, i.e., lithologic composite oil and gas reservoirs, under complex external environmental conditions.

[0003] In the past decade of seismic exploration, a technical strategy centered on the "dual high" processing and interpretation of lithology has been gradually formed. This strategy has the advantages of amplitude preservation and high resolution, and has achieved relatively high resolution and high fidelity processing of seismic results. However, traditional velocity modeling methods have not been able to effectively reduce the ambiguity of lithological internal imaging. The identification and control of strike-slip faults are still in the exploratory stage. They cannot meet the requirements of imaging accuracy for heterogeneous geological targets, nor can they meet the needs of fine characterization of platform margins and accurate identification of lithological traps. Summary of the Invention

[0004] This invention aims to provide a method for establishing a plastic formation velocity model, which effectively reduces the ambiguity of lithological internal imaging, achieves the goal of imaging heterogeneous geological targets with ambiguity, and realizes a more refined and reliable characterization of ultra-deep heterogeneous reservoirs.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for establishing a plastic formation velocity model, characterized in that the method includes the following steps performed sequentially:

[0007] S1. Establish the final overburden velocity model of the plastic formation, and perform fine picking of the top and bottom layers of the plastic formation. Fill in the plastic formation velocity according to the well logging information to establish the initial velocity model of the plastic formation.

[0008] S2. Update the initial velocity model of the plastic formation based on the variable velocity model operator and the all-round grid tomography technique to obtain the final velocity model of the plastic formation;

[0009] S3. Merge and stitch the final plastic stratum velocity model and the final plastic stratum overlying velocity model to obtain the merged velocity model;

[0010] S4. Based on the fused and spliced ​​velocity model, establish a velocity model of the underlying formation of the plastic formation according to drilling and logging information, and obtain the final velocity model through update and iteration.

[0011] As a limitation, the process of establishing the final overburden velocity model of the plastic strata in step S1 is as follows:

[0012] S11. Obtain a shallow near-surface model by initial arrival inversion under well logging constraints; establish a geological stratification velocity model based on drilling information;

[0013] S12. The shallow near-surface model and the geological stratification velocity model are fused to obtain the initial velocity model of the overlying strata;

[0014] S13. Perform pre-stack depth migration on the initial velocity model of the overlying strata to obtain depth migration gathers and depth migration data volumes.

[0015] S14. Pick up the remaining delay from the depth migration gather, use grid tomography to obtain the velocity update, and update the initial velocity model of the overlying strata.

[0016] S15. Repeat steps S13 to S14 for the updated overlying strata initial velocity model until the final overlying strata velocity model is obtained.

[0017] As a second limitation, the mesh tomography technique in step S14 specifically refers to:

[0018] The remaining delay is converted into the remaining velocity value. The slowness matrix equation for all rays is established within the grid. The velocity update for each grid is obtained by solving the matrix equation.

[0019] As a third limitation, the final overlying formation velocity model in step S15 is characterized by: a straight depth migration reflection phase axis and a vertical gradient that matches the logging velocity.

[0020] As a fourth limitation, the specific process for obtaining the final plastic formation velocity model in step S2 is as follows:

[0021] S21. Construct a variable velocity model operator based on the seismic profile obtained from pre-stack depth migration, and update the variable velocity model operator by multiplying it with the initial velocity model of the plastic strata to obtain the updated initial velocity model of the plastic strata.

[0022] S22. The updated initial velocity model of the plastic formation is further updated using the all-round grid tomography technique to obtain the velocity model of the plastic formation.

[0023] S23. Continue to perform pre-stack depth migration on the plastic strata velocity model, and adjust and characterize the plastic strata interface based on the results of the pre-stack depth migration to obtain the migrated seismic profile.

[0024] S24. Repeat steps S21 to S23 until the depth residual of the variable velocity model operator approaches zero, thus obtaining the final plastic formation velocity model.

[0025] As a fifth limitation, the specific process of constructing the variable speed model operator in step S21 is as follows:

[0026] S211. Use drilling data to identify and pick up plastic formations, and carry out P-wave velocity inversion based on seismic wave field dynamic characteristics within the plastic formations to obtain the plastic formation velocities with longitudinal variation trends.

[0027] S212. Using the plastic stratum velocity with a vertical variation trend as the initial velocity of the plastic stratum, pre-stack depth migration is performed to obtain the migrated seismic profile. There is a depth residual between the bottom interface of the plastic stratum in the migrated seismic profile and the bottom interface of the stratum in the actual drilling results. The depth residual is the time difference between the top and bottom layers of the plastic stratum.

[0028] S213. Pick up the depth residual and convert the depth residual into the velocity residual of the plastic formation, that is, the variable velocity model operator of the plastic formation.

[0029] As a sixth limitation, the omnidirectional mesh tomography technique in step S22 specifically refers to:

[0030] The remaining delay is converted into the remaining velocity value. All rays are divided into multiple groups in different directions according to their paths. For each group, the slowness matrix equation of all rays is established in the grid. Multiple sets of matrix equations are established in total. The velocity update of each grid is obtained by solving multiple sets of matrix equations.

[0031] As a seventh limitation, the update and iteration process in step S4 is as follows: the velocity model of the underlying strata of the plastic formation is updated using grid tomography and pre-stack depth migration is performed until the depth migration reflection phase axis is straight and the vertical change gradient matches the logging velocity, thus obtaining the final velocity model.

[0032] Another object of the present invention is to provide an electronic device, including a memory and a processor, wherein the memory stores a computer program, characterized in that the processor executes the computer program to implement the steps of a method for establishing a plastic formation velocity model.

[0033] Another object of the present invention is to provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a method for establishing a plastic formation velocity model.

[0034] By adopting the above-described technical solution, the beneficial effects achieved by this invention compared to the prior art are as follows:

[0035] (1) Based on the traditional well logging layer velocity, the method of the present invention analyzes and identifies the seismic geological occurrence, combines the velocity structure scanning of plastic strata, constructs a variable velocity model operator with fine structure, and uses all-round grid tomography technology to update and iterate the velocity field, and finally creates a velocity model corresponding to the plastic strata, improves the resolution of high-frequency velocity changes, focuses the accurate positioning of common reflection points, and can make the carbonate strata imaging clearer and the fault and fracture characterization more accurate.

[0036] (2) The method of the present invention makes full use of drilling and logging, seismic and geological results to perform high-precision layer velocity engraving of gypsum-salt plastic strata and their overlying and underlying strata from shallow to deep, improves the resolution of high-frequency velocity changes, focuses the accurate positioning of common reflection points, effectively reduces the ambiguity of lithological internal imaging, and achieves a more refined and reliable characterization of ultra-deep heterogeneous reservoirs.

[0037] (3) The method of this invention solves the problem of imaging distortion of underlying strata caused by the longitudinal and lateral transformation of the velocity of the overlying plastic strata. The well-seismic error is significantly ahead of the industry standard, enabling a more refined characterization of ultra-deep heterogeneous reservoirs, greatly improving the reliability of seismic results for lithological targets, effectively supporting the implementation of deep carbonate strata targets, supporting subsequent well location deployment and tracking research, providing a basis for further thin reservoir prediction and well location deployment.

[0038] In summary, this invention effectively reduces the ambiguity of lithological internal imaging, enabling a more refined and reliable characterization of ultra-deep heterogeneous reservoirs. Attached Figure Description

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0040] Figure 1 This is a flowchart of the method in Embodiment 1 of the present invention;

[0041] Figure 2 This is a schematic diagram of the plastic formation velocity obtained by inversion in Embodiment 1 of the present invention;

[0042] Figure 3 This is a schematic diagram of the variable speed model operator for plastic formations in Embodiment 1 of the present invention;

[0043] Figure 4(a) is a schematic diagram of the pre-stack depth offset profile obtained before applying Embodiment 1 of the present invention;

[0044] Figure 4 (b) is a schematic diagram of the pre-stack depth offset profile of Embodiment 1 of the present invention;

[0045] Figure 5 (a) is a schematic diagram of the final velocity model of Embodiment 1 of the present invention;

[0046] Figure 5 (b) is a graph showing the logging speed and depth offset speed of Embodiment 1 of the present invention. Detailed Implementation

[0047] To better explain and facilitate understanding of the present invention, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0048] Example 1: A method for establishing a plastic formation velocity model

[0049] This embodiment uses the plastic gypsum-bearing folded strata of the carbonate reservoir in Basin A of my country as the study area. Figure 1 As shown, this embodiment includes the following steps performed sequentially:

[0050] S1. Establish the velocity model of the overlying strata of the final plastic strata, and perform fine picking of the top and bottom layers of the plastic strata. Fill in the plastic strata velocity based on the well logging information to establish the initial velocity model of the plastic strata.

[0051] S11. Under well logging constraints, the shallow near-surface model is obtained through initial arrival inversion; a geological stratification velocity model is established based on drilling information.

[0052] S12. The shallow near-surface model and the geological stratification velocity model are fused to obtain the initial velocity model of the overlying strata.

[0053] S13. Perform pre-stack depth migration on the initial velocity model of the overlying strata to obtain depth migration gathers and depth migration data volumes.

[0054] S14. Pick up the remaining delay for the depth migration gather, use grid tomography to obtain the velocity update, and update the initial velocity model of the overlying strata.

[0055] The mesh tomography technique specifically involves converting the residual delay into a residual velocity value, establishing a slowness matrix equation for all rays within the mesh, and obtaining the velocity update for each mesh by solving the matrix equation, where slowness is the reciprocal of velocity.

[0056] S15. Repeat steps S13 to S14 for the updated overburden initial velocity model until a final overburden velocity model is obtained where the depth migration reflection phase axis is straight and the vertical gradient matches the logging velocity.

[0057] S2. Update the initial velocity model of the plastic formation based on the variable velocity model operator and the all-round grid tomography technique to obtain the final velocity model of the plastic formation.

[0058] S21. Construct a variable velocity model operator based on the seismic profile obtained from pre-stack depth migration, and update the variable velocity model by multiplying it with the initial velocity model of the plastic strata to obtain the updated initial velocity model of the plastic strata.

[0059] S211. Identify and extract plastic formations using drilling data, and perform P-wave velocity inversion within the plastic formations based on seismic wavefield dynamics characteristics to obtain, for example... Figure 2 The velocity of the plastic formation is shown to have a vertical variation trend.

[0060] S212. Using the vertically varying plastic stratum velocity as the initial velocity of the plastic stratum, pre-stack depth migration is performed to obtain the migrated seismic profile. The bottom interface of the plastic stratum in the migrated seismic profile has a depth residual with the bottom interface of the stratum in the actual drilling results. The depth residual is the time difference between the top and bottom layers of the plastic stratum.

[0061] S213. Pick up the depth residual and convert it into the velocity residual of the plastic formation, i.e. Figure 3 The variable-speed model operator for the plastic formation is shown.

[0062] S22. The updated initial velocity model of the plastic formation is further updated using omnidirectional grid tomography to obtain the velocity model of the plastic formation.

[0063] The omnidirectional grid tomography technique specifically involves converting the residual delay into residual velocity values, dividing all rays into multiple groups according to their paths, establishing a slowness matrix equation for all rays in each group within the grid, establishing multiple sets of matrix equations, and obtaining the velocity update for each grid by solving multiple sets of matrix equations.

[0064] S23. Continue to perform pre-stack depth migration on the plastic strata velocity model, and adjust and characterize the plastic strata interface based on the results of the pre-stack depth migration to obtain the migrated seismic profile.

[0065] S24. Repeat steps S21 to S23 until the depth residual of the variable velocity model operator approaches zero, thus obtaining the final plastic formation velocity model.

[0066] S3. The final plastic stratum velocity model and the final plastic stratum overlying velocity model are fused and spliced ​​together to obtain the fused and spliced ​​velocity model.

[0067] S4. Based on the fused and spliced ​​velocity model, a velocity model of the underlying formation of the plastic formation is established according to drilling and logging information. Through updating and iteration, that is, continuously using grid tomography to update the velocity model of the underlying formation of the plastic formation for pre-stack depth migration, until a velocity model with a straight depth migration reflection phase axis and a vertical gradient that matches the logging velocity is obtained is taken as the final velocity model.

[0068] Figure 4 (a) shows the pre-stack depth offset profile obtained before applying this embodiment. Figure 4 (b) shows the pre-stack depth migration profile obtained after applying this embodiment. By comparison, it can be seen that the pre-stack depth migration results using the final velocity model of this embodiment are more focused and have higher resolution than those without applying the plastic strata velocity. The undulation of the underlying strata is not affected by the plastic strata attitude. In the application of pre-stack depth migration in a certain area of ​​Basin A, it is consistent with the drilling conclusions and geological understanding.

[0069] Figure 5 (a) shows a schematic diagram of the depth migration profile and layer velocity superposition of the final velocity model obtained using this embodiment; Figure 5 (b) shows the logging velocity and depth migration velocity curves. Figure 5 (b) In this model, M represents the depth migration velocity and N represents the logging velocity. Through comparative analysis, it can be seen that the longitudinal and lateral variation trends of this velocity model are highly consistent with the logging velocity.

[0070] Table 1 shows the well seismic error statistics for the study area in this embodiment. The table lists the names of the strata in the depth migration profile, the drilling elevation imaging depth, the actual drilling depth at drilling elevation, the depth error, and the error rate.

[0071] Table 1. Statistical Table of Well Seismic Errors in the Study Area

[0072]

[0073]

[0074] As shown in the table, the error rates of both the drilling elevation imaging depth and the actual drilling depth are significantly better than the industry standard, i.e., the well vibration error is 1%, which proves the accuracy of the characterization speed after applying this embodiment.

[0075] Example 2: Electronic device and computer-readable storage medium based on the method for establishing a plastic formation velocity model

[0076] The electronic device in this embodiment is a computer device, which mainly includes one or more processors and a memory. This embodiment takes one processor as an example.

[0077] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations thereof. The general-purpose processor can be a microprocessor or any conventional processor. The memory stores a computer program; when the processor executes the computer program, it can implement the steps of the method for establishing the plastic formation velocity model in Example 1.

[0078] A computer-readable storage medium stores a computer program thereon, which, when executed by a processor, implements the steps of the method for establishing the plastic formation velocity model of Embodiment 1. The computer program includes computer program code, which may be in the form of source code, object code, executable file, or some intermediate form. The computer-readable storage medium includes: any entity or device capable of carrying the computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

Claims

1. A method of building a plastic interval velocity model, characterized in that, The method comprises the following steps in sequence: S1, establishing an overlying velocity model of the final plastic stratum; fine picking the top layer and the bottom layer of the plastic stratum, filling the velocity of the plastic stratum according to the logging information, and establishing an initial velocity model of the plastic stratum; S2, updating the initial velocity model of the plastic stratum according to a variable velocity model operator and a full-azimuth grid tomography technology to obtain a final velocity model of the plastic stratum; S3, fusing and splicing the final velocity model of the plastic stratum and the final overlying velocity model of the plastic stratum to obtain a fused and spliced velocity model; S4, on the basis of the fused and spliced velocity model, establishing a velocity model of the underlying stratum of the plastic stratum according to drilling and logging information, and obtaining a final velocity model through updating iteration.

2. The method of establishing a plastic interval velocity model according to claim 1, wherein, The process of establishing the final overlying velocity model of the plastic stratum in the step S1 is as follows: S11, obtaining a shallow near-surface model through first arrival inversion under the constraint of logging; establishing a geologic layered velocity model according to drilling information; S12, fusing the shallow near-surface model and the geologic layered velocity model to obtain an initial overlying velocity model; S13, performing pre-stack depth migration on the initial overlying velocity model to obtain a depth migration gather and a depth migration data body; S14, picking a residual delay amount from the depth migration gather, obtaining a velocity update amount by using a grid tomography technology, and updating the initial overlying velocity model; S15, repeatedly executing the steps S13 to S14 on the updated initial overlying velocity model until a final overlying velocity model is obtained.

3. The method of establishing a plastic interval velocity model of claim 2, wherein, The grid tomography technology in the step S14 is specifically as follows: The residual delay amount is converted into a residual velocity value, a slowness matrix equation of all rays is established in a grid, and a velocity update amount of each grid is obtained by solving the matrix equation.

4. The method of establishing a plastic interval velocity model according to claim 3, wherein, The final overlying velocity model in the step S15 is characterized in that: depth migration reflection events are straight, and a longitudinal variation gradient is consistent with a logging velocity.

5. The method of claim 1-4, wherein The specific process of obtaining the final velocity model of the plastic stratum in the step S2 is as follows: S21, constructing a variable velocity model operator according to a seismic profile obtained through pre-stack depth migration, multiplying the variable velocity model operator and the initial velocity model of the plastic stratum to perform updating, and obtaining an updated initial velocity model of the plastic stratum; S22, further updating the updated initial velocity model of the plastic stratum by using a full-azimuth grid tomography technology to obtain a velocity model of the plastic stratum; S23, continuously performing pre-stack depth migration on the velocity model of the plastic stratum, and adjusting and depicting a plastic stratum interface on the result of the pre-stack depth migration to obtain a migrated seismic profile; S24, repeatedly executing the steps S21 to S23 until a depth residual error of the variable velocity model operator tends to zero, that is, a final velocity model of the plastic stratum is obtained.

6. The method of establishing a plastic interval velocity model of claim 5, wherein, The specific process of constructing the variable velocity model operator in the step S21 is as follows: S211, identifying and picking the plastic stratum by using drilling data, performing P-wave velocity inversion based on the dynamic characteristics of a seismic wave field in the plastic stratum, and obtaining a plastic stratum velocity with a longitudinal variation trend; S212, performing pre-stack depth migration with the plastic formation velocity with a longitudinal variation trend as an initial velocity of the plastic formation to obtain a migrated seismic profile, wherein a bottom interface of the plastic formation of the migrated seismic profile has a depth residual error with a bottom interface of the formation of the actual drilling result, and the depth residual error is an interval travel time of a top layer and a bottom layer of the plastic formation; S213, picking up the depth residual error, and converting the depth residual error into a velocity residual error of the plastic formation, i.e., a velocity variation model operator of the plastic formation.

7. The method of establishing a plastic interval velocity model of claim 5, wherein, The step S22 is specifically: The residual delay is converted into a residual velocity value, all rays are divided into different groups according to paths, a slowness matrix equation of all rays is established in a grid for each group, a plurality of matrix equations are established, and a velocity update of each grid is obtained by solving the plurality of matrix equations.

8. The method of establishing a plastic interval velocity model of claim 7, wherein, The step S4 is specifically: 9.An electronic device comprising a memory and a processor, the memory storing a computer program, wherein, The grid tomography technique is used to update the velocity model of the underlying formation of the plastic formation to perform the pre-stack depth migration until the depth migration reflection phase axis is flat and the longitudinal variation gradient is consistent with the logging velocity, i.e., a final velocity model is obtained. The processor executes the computer program to realize the steps of the method in any one of claims 1-8.

10. A computer readable storage medium, having a computer program stored thereon, the computer program being executed by a processor to realize the steps of the method in any one of claims 1-8.

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