Background
In seismic exploration, particularly in oil and gas reservoir exploration, complex fault block imaging and structure implementation become key factors, and a series of geological risk factors corresponding to structure trapping implementation, reservoir carving, accurate drilling target entering and the like are all urgent to be considered in actual exploration, so that the geological exploration is usually faced with two problems: imaging accuracy and structural distortion.
The prestack depth migration is a currently accepted method for effectively solving seismic imaging, but the imaging precision of the prestack depth migration depends on the rationality of a depth-velocity model to a great extent, so that the depth-velocity model is usually optimized by means of a tomography method (namely, a tomography inversion method) and data driving, the tomography method needs to explain a horizon by modeling along the horizon, and the influence of a fracture system on the model is not considered; for relying on data-driven, it makes full use of the acquired seismic data information to perform velocity modeling. Due to the limitation of the principle of the tomography method, uncertainty is easy to occur in tomography inversion speed modeling during inversion solving, so that the inverted speed model is difficult to be matched with a real geological structure, particularly, under the condition of complex fault block development, the speed modeling by using the tomography inversion method is difficult to meet the exploration evaluation requirement of a target area, and one important reason is that well seismic closure difference cannot be eliminated, so that the seismic depth and the well depth have errors.
At present, no speed modeling method which is good and effective for eliminating the well seismic closure difference exists. The relevant references are as follows:
1. the application of the complex structure modeling technology in seismic inversion [ J ]. geophysical exploration of petroleum, 2018,53 (supplement & supplement): 270-class 275.
2. Scheffer, Dumin, Wenpeng, etc. the application of the grid chromatography speed inversion method in quasi-three-dimensional Xisha hydrate [ J ]. geophysical prospecting and chemical prospecting, 2017,41(5): 846-.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a speed modeling method capable of eliminating well seismic closure difference, which can solve the problem of eliminating the well seismic closure difference;
the second object of the present invention is to provide a processing terminal, which can solve the problem of eliminating the poor closing of the well earthquake.
The technical scheme for realizing one purpose of the invention is as follows: a velocity modeling method capable of eliminating well seismic closure difference comprises the following steps:
step 1: obtaining a depth domain layer velocity model, wherein the depth domain layer velocity model at least comprises velocity three-component information, the velocity three-component information comprises inclination angle, continuity and azimuth angle information, and performing prestack depth migration calculation on the depth domain layer velocity model to obtain a prestack depth migration profile and a common imaging point gather of prestack depth migration;
step 2: associating the well marks with the horizons, reestablishing a structural model containing well information and well layers according to the method in the step 2, and calculating well seismic closure differences corresponding to each well layer;
and step 3: obtaining a depth domain layer velocity model after well seismic closure difference updating iteration by keeping travel time tomography, thereby obtaining a depth domain layer velocity model after well seismic closure difference updating iteration under fault control, velocity three-component information of the depth domain layer velocity model and an updated anisotropic parameter model;
and 4, step 4: simultaneously updating the obtained three-component information of the velocity into the construction model in the step 2, recalculating a new round of well seismic closure difference for the new construction model, and performing prestack depth migration calculation on the depth domain layer velocity model after the updating iteration obtained in the step 3 again according to the newly calculated well seismic closure difference and the updated anisotropic parameter model in the step 3 to obtain a corresponding prestack depth migration gather and a prestack depth migration profile;
and 5: and (4) repeating the steps 2-4 to perform optimization iteration on the depth domain layer velocity model until the depth domain layer velocity model after the optimization iteration meets the imaging geological requirements, and performing prestack depth migration volume migration according to the final depth domain layer velocity model to obtain a final imaging result profile so as to finish velocity modeling.
The second technical scheme for realizing the aim of the invention is as follows: a processing terminal comprising, a memory for storing program instructions;
a processor for executing the program instructions to perform the steps of the velocity modeling method for eliminating the well-seismic closure difference.
The invention has the beneficial effects that: the velocity model established by the invention can effectively solve the problem of errors of seismic depth and well depth, provides reliable seismic data for target evaluation, effectively reduces exploration risks and improves the precision of the velocity model.
Drawings
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a schematic diagram of a depth domain initial layer velocity model;
FIG. 3 is a schematic diagram of a tectonic model established under fault control;
FIG. 4 is a schematic illustration of a residual time difference;
FIG. 5 is an updated depth domain layer velocity model obtained by a tomographic inversion method with formation model constraints;
FIG. 6(a) is a velocity comparison diagram of the depth domain initial layer velocity model and the depth domain layer velocity model obtained through tomography at the point A of the fault footwall;
FIG. 6(B) is a velocity comparison diagram of the depth domain initial layer velocity model and the tomographic depth domain layer velocity model at the B point on the slice;
FIG. 7 is a schematic diagram showing the superposition of a depth domain interval velocity model and a seismic prestack section;
FIG. 8 is a schematic diagram of the dip angle of the velocity three-component information of the depth domain layer velocity model obtained by the processing of this step;
FIG. 9 is an azimuth schematic diagram of the velocity three-component information of the depth domain layer velocity model obtained by the processing of this step;
FIG. 10 is a schematic view of the joint display of four wells (numbered W01-W04) with fault and horizon model information;
FIG. 11 is a three-dimensional visualization display of well seismic closure differences;
FIG. 12 is a schematic diagram showing a well layer velocity model and a well layer display before travel time tomography inversion (the well depth and the horizon depth after velocity inversion have a certain depth error);
FIG. 13 is a schematic view showing a depth domain interval velocity model and a well stratification after travel time tomography inversion (the well depth and the depth of the interval after velocity inversion have a certain depth error of zero);
fig. 14 is a schematic structural diagram of a processing terminal according to the present invention.
Detailed description of the preferred embodiments
The invention will be further described with reference to the accompanying drawings and specific embodiments:
as shown in fig. 1-13, a velocity modeling method for eliminating well seismic closure difference includes the following steps:
step 1: acquiring seismic data including shot line data, performing conventional denoising processing on the seismic data in a sequence time domain to obtain a common midpoint gather, and establishing a depth domain initial layer velocity model according to the common midpoint gather. The root mean square velocity of the time domain can be used for establishing a time domain initial layer velocity model which accords with the geological velocity change rule through a CVI constraint velocity inversion method, and the time-depth (namely the time domain-depth domain) conversion is utilized to obtain a depth domain initial layer velocity model. The rms velocity in the time domain may be picked from the common midpoint gather after conventional processing, which generally includes preprocessing, various noise suppression (linear or non-linear noise, multiples, etc.), horizontal stacking, and stack shifting. And then, carrying out travel time calculation based on ray tracking on the depth domain initial layer velocity model, and carrying out prestack depth migration calculation on the depth domain initial layer velocity model according to the calculated travel time so as to obtain a prestack depth migration profile and a common imaging point gather (CIG) of prestack depth migration. FIG. 2 is a schematic diagram of a depth-domain initial layer velocity model, wherein the velocity values range from 3651m/s to 6500 m/s.
Step 2: and establishing a construction model, wherein the construction model comprises a fault model and a horizon model. Firstly, defining fault and stratum properties, loading fault and stratum information to establish a fault grid and fault blocks, then establishing a layer grid, and establishing a geological grid according to the fault grid, the fault blocks and the layer grid, thereby establishing a structural model. Fig. 3 is a schematic diagram of a structural model established under fault control, which includes fault grids and main horizon information.
And step 3: and picking up the residual time difference of the common imaging point gather, wherein the residual time difference can be used as the estimation of the non-levelness degree of the common imaging point gather of the pre-stack depth deviation, namely leveling the common imaging point gather. The method for calculating the residual time difference is the prior art and is not described herein again. Fig. 4 is a schematic diagram of the residual time difference.
And 4, step 4: and (3) taking the depth domain initial layer velocity model obtained in the step (1), the construction model obtained in the step (2) and the residual time difference obtained in the step (3) as a first comprehensive database, wherein the first comprehensive database is used for providing basic data for subsequent chromatographic inversion.
And 5: and (3) performing updating iteration processing on the depth domain initial layer velocity model in the step (1) for at least two times by adopting a tomography inversion method based on the structural model constraint in the step (2) to obtain a final updated depth domain layer velocity model. In the updating iteration processing process, the residual time difference is used as soft constraint of geological grid information input, the constraint item controls the deviation of the current layer velocity model and the previous layer velocity model in each iteration process, so that the updated and iterated depth domain layer velocity model and velocity three-component information of the depth domain layer velocity model are obtained, and the velocity three-component information comprises inclination angle, continuity and azimuth angle information. The depth domain initial layer velocity model which is not updated does not have velocity three-component information, and only the depth domain layer velocity model after at least one tomography iteration based on the structural model constraint. FIG. 5 is an updated depth domain layer velocity model obtained by a tomography inversion method constrained by a structural model, and the updated depth domain layer velocity model can accurately depict underground structural features and can truly represent complex underground geological features. FIG. 6(a) is a velocity comparison diagram of the depth domain initial layer velocity model and the depth domain layer velocity model obtained through tomography at the point A of the fault footwall; fig. 6(B) is a velocity comparison diagram of the depth domain initial layer velocity model and the tomography depth domain layer velocity model at the disk B point on the fault, wherein the left graph is the depth domain initial layer velocity model, and the right graph is the tomography depth domain layer velocity model. In fig. 6(a) and 6(b), taking the main line 720 as an example, by comparison, it is found that: the speed of the initial layer speed model in the depth domain at the point A of the lower wall of the fault is 4308.24m/s, the speed of the point B of the upper wall of the fault is 4306.7m/s, and the speed difference at the upper wall and the lower wall of the fault (point BA) is 1.54 m/s; the speed of the depth domain layer velocity model obtained through tomography at the point A of the lower disc of the fault is 4346.79m/s, the speed of the point B of the upper disc of the fault is 4504.5m/s, and the difference of the speeds at the upper disc and the lower disc of the fault (point BA) is 157.71 m/s. Therefore, the depth domain layer velocity model obtained after tomography based on the structural model can accurately depict the velocity difference between the upper and lower plates of the broken layer.
FIG. 7 is a schematic diagram of superposition display of a depth domain layer velocity model and a seismic prestack section, and from FIG. 7, it can be seen that the depth domain layer velocity model obtained through structural model constraint and a corresponding structural model keep high geological consistency, a velocity field is high in matching degree with real underground geology, fault imaging is effectively depicted, and the accurate position of fault trapping is realized.
In this step, the tomography inversion method generally includes methods such as grid tomography, tomography based on a structural model, and travel-time-keeping tomography, and the tomography inversion method is substantially an optimization problem, and aims to find a layer velocity model to minimize an objective function (or called a cost function), where the objective function mathematically quantifies the unflattened degree of a gather under the conditions of satisfying specific soft constraints (geological information input), hard constraints (well seismic closure difference: the maximum matching between a migration result and well data), and geological factor constraints, and the tomography inversion method belongs to the prior art and is not described in detail.
Step 6: and (5) taking the speed three-component information of the depth domain layer speed model obtained through the first round of updating iterative processing in the step (5) and the geological grid information as input to participate in the building of the structural model in the step (2), so as to obtain a new structural model. Meanwhile, pre-stack depth migration calculation is carried out on the depth domain layer velocity model obtained through the first round of updating iteration processing, and a new pre-stack depth migration profile and a new pre-stack depth migration common imaging point gather are obtained. FIG. 8 is a schematic diagram of the dip angles of the velocity three-component information of the depth domain layer velocity model obtained by the processing of this step, wherein the dip angle range of the velocity three-component is approximately about 0-40 °; fig. 9 is an azimuth schematic diagram of the three-component velocity information of the depth domain layer velocity model obtained by the processing in this step, wherein the azimuth range of the three-component velocity is approximately 10-320 ° in azimuth.
And then, repeating the steps 2-6 to perform optimization iteration of the depth domain layer velocity model until the objective function C (m) reaches the minimum value, and otherwise, continuing the optimization iteration. When the objective function C (m) reaches the minimum value, the optimized and iterated depth domain layer velocity model accords with imaging geological requirements, a final depth domain layer velocity model is correspondingly obtained, pre-stack depth migration calculation is carried out on the final depth domain layer velocity model, a final imaging result profile is obtained, namely, a high-precision layer velocity model under fault control is obtained, and velocity modeling is completed.
Through the processing of the steps 1 to 6, a high-precision layer velocity model under fault control can be obtained, the geological velocity modeling problem is solved, a set of targeted solution is provided for the problems (structure trapping and closing, reservoir carving and accurate drilling target entering) faced by the current exploration and development, the structural complexity of an underground medium is fully considered, the change characteristics of the velocities on two sides of a fault block are accurately carved, and the velocity model with the constraint of the geological structure model and the corresponding structure model keep high geological consistency.
And 7: and (5) directly entering the step, and performing prestack depth migration calculation according to the depth domain layer velocity model obtained in the step (5) to obtain a prestack depth migration profile and a common imaging point gather of prestack depth migration.
And 8: and (3) associating the well mark (marker) with the horizon, reestablishing a structural model containing well information and well layers according to the method in the step (2), and calculating the well seismic closure difference corresponding to each well layer. FIG. 10 is a schematic diagram of the joint display of four wells (numbered W01-W04) and fault and horizon model information. FIG. 11 is a three-dimensional visualization of well seismic closure differences, which are shown to have a depth range of-200-0.
And step 9: and (5) establishing a second comprehensive database, wherein the second comprehensive database comprises the construction model in the step (8), the well seismic closure error and the depth domain layer velocity model subjected to the chromatographic optimization of the construction model in the step (5).
Step 10: and keeping the travel time tomography to obtain well seismic closure error and updating the iterated depth domain layer velocity model. The method of preserving travel-time tomography is essentially applied by a process of building and solving matrices in which the first thomson parameter δ and the second thomson parameter e are equal in value. In this embodiment, data of the second integrated database are fused, so that a depth domain layer velocity model after fault control downhole seismic closure error update iteration, velocity three-component information of the depth domain layer velocity model, and an updated anisotropic parameter model are obtained. Wherein, the travel-time tomography process is actually a process Ax ═ b of a linear equation set solved by tomographic velocity inversion, wherein A is a matrix with dimension m multiplied by n, x is an array with dimension n multiplied by 1, and the physical meaning represented by the process is a slowness value (slowness change value) in each grid; b is an m x 1 dimensional array representing the physical meaning of the travel time (travel time difference) of the ray; dimension m represents the total number of rays and n is the number of meshes of the velocity model. The updated anisotropic parameter model will be used as input information for the second integrated database in the subsequent travel-time tomography iteration process. Since the tomographic imaging method while keeping traveling belongs to the prior art, it will not be described herein. Fig. 12 is a schematic diagram showing a depth domain layer velocity model and a well layer display before travel time tomography inversion (a certain depth error exists between the well depth and the depth of a layer after velocity inversion), and it can be seen from fig. 12 that a certain depth error exists between the well depth of four wells numbered W01-W04 and the depth of a layer after velocity inversion, wherein the position of a vertical third well marker of each well is not coincident with the depth of a nearby horizontal layer (a solid line curve), that is, a certain depth error exists between the well depth of four wells numbered W01-W04 and the depth of a layer after velocity inversion; and fig. 13 is a schematic diagram showing a depth domain layer velocity model and a well layering display after travel tomography inversion (the well depth and the depth of a position after velocity inversion have a certain depth error of zero), and the position of a vertical third well mark marker of each channel in the diagram is overlapped with the depth of a position (a solid curve) in a horizontal direction nearby, so that the problem of the error of the seismic depth and the well depth is effectively solved, and a direct data basis can be provided for operations such as drilling accurate target entering and the like.
Step 11: and simultaneously updating the three-component information of the velocity obtained in thestep 10 into the structural model in the step 8, recalculating the new well-seismic closure difference for the new structural model, updating the newly calculated well-seismic closure difference and the updated anisotropic parameter model in thestep 10 into a second comprehensive database to serve as a new second comprehensive database, and performing prestack depth migration calculation on the updated and iterated layer velocity model obtained in thestep 10 to obtain a corresponding prestack depth migration gather and a prestack depth migration profile.
Step 12: and after the step 11 is completed, repeating the step 8 to the step 11 to perform optimization iteration on the depth domain layer velocity model until the depth domain layer velocity model after the optimization iteration meets the imaging geological requirements, and performing prestack depth migration volume migration according to the final depth domain layer velocity model to obtain a final imaging result profile.
Through the processing of the steps 1-5 and 7-12, a set of targeted solution can be provided for a series of problems of structural confinement implementation, reservoir carving, accurate target entering of drilling and the like faced by exploration and development at present, the problems of errors of seismic depth and well depth are effectively solved by ensuring a velocity model and imaging precision through fault control, reliable seismic data are provided for target evaluation, exploration risks are effectively reduced, and the precision of the velocity model is improved.
As shown in fig. 14, the present invention also provides an entityimplementation processing terminal 100 of a high-precision velocity modeling method under fault control, which includes,
amemory 101 for storing program instructions;
aprocessor 102 for executing the program instructions to perform the steps of the high precision velocity modeling method under fault control.
The embodiments disclosed in this description are only an exemplification of the single-sided characteristics of the invention, and the scope of protection of the invention is not limited to these embodiments, and any other functionally equivalent embodiments fall within the scope of protection of the invention. Various other changes and modifications to the above-described embodiments and concepts will become apparent to those skilled in the art from the above description, and all such changes and modifications are intended to be included within the scope of the present invention as defined in the appended claims.