A method for obtaining anisotropic parameters in VSP drive processing while drilling

Abstract

The present invention discloses a method for obtaining anisotropic parameters of while-drilling VSP drive processing, comprising the following steps: S1, collecting basic seismic data; S2, collecting VSP data; S3, carrying out velocity field correction and optimization, taking the collected drilling, logging and geological information as constraint conditions, and re-optimizing and correcting the velocity field; S4, calculating a new anisotropic parameter δ new ; S5, anisotropic parameter optimization and iteration, update to obtain ε body; S6, use the updated anisotropic parameters to perform anisotropic depth migration, determine whether the CIP gather is flattened, if flattened, output the final imaging data body, if not flattened, return to S5. The present invention can make full use of the anisotropic parameters, anisotropic velocity and new iteration velocity of the existing data to quickly and accurately calculate the new anisotropic parameters.

Description

Technical Field

[0001] The invention belongs to the technical field of geophysical exploration and development of oil and natural gas, and in particular relates to a method for obtaining anisotropic parameters for while-drilling VSP drive processing. Background Art

[0002] The layout of shale gas horizontal wells and the prediction of carbonate fracture-cave reservoirs have put forward higher requirements for the depth domain imaging accuracy of seismic data, especially the Tarim fracture-cave reservoir, which has a small reservoir scale and strong heterogeneity, and has extremely high requirements for imaging accuracy. While-drilling VSP drive processing is an integrated engineering, geophysical and geological method developed in recent years to improve the accuracy of deep-domain imaging. The most important problem that while-drilling VSP drive processing needs to solve is the accuracy and timeliness of seismic imaging. However, most of the domestic oil and gas reservoirs are in deep high-speed areas. Due to the limitations of offset distance and signal-to-noise ratio, the sensitivity of seismic data to velocity decreases with the increase of depth and velocity. In addition, the existence of seismic velocity multi-solutions makes it impossible to obtain the precise velocity of the target position by relying solely on seismic data; at the same time, deep underground media often have strong anisotropy. Therefore, in order to obtain high-precision imaging quality, high-quality anisotropic parameters must be obtained. In order to improve the imaging accuracy, velocity modeling accuracy, and anisotropic parameter calculation accuracy, logging data and other data are usually introduced into velocity modeling, and multi-information constraints are used to achieve the purpose of velocity refinement.

[0003] The traditional anisotropic parameter modeling based on well-seismic combined grid tomography usually adopts the idea of ​​first inverting the P-wave velocity and δ body, and then inverting the ε body separately. Among them, interpolating the well-seismic errors at the well point location is a very important link, because the well data information is the key to obtaining anisotropic parameters, but the distribution of wells is generally sparse, which requires interpolating the well-seismic errors at the classic locations to predict the depth errors at other locations, so as to obtain the anisotropic parameters within the entire work area.

[0004] Although the traditional anisotropic parameter calculation method can obtain relatively accurate anisotropic parameters, it takes a lot of time to match well and seismic data, analyze well and seismic errors, and calculate anisotropic parameters. Since all work needs to be completed within 72 hours for the while-drilling VSP drive processing, it is particularly important to calculate anisotropic parameters efficiently and accurately. If the anisotropic parameters are calculated according to the traditional method, the calculation effect will definitely not be met, because the calculation time for simply calculating the anisotropic parameters will far exceed 72 hours. While-drilling processing is based on archived data and is a reuse of archived results data. The results data already contains anisotropic parameter information obtained based on known wells. Compared with new drilling information, the accuracy of its anisotropic parameters is questionable. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an anisotropic parameter obtaining method for while drilling VSP drive processing which can fully utilize the anisotropic parameters, anisotropic velocity and new iteration velocity of existing data to quickly and accurately calculate new anisotropic parameters.

[0006] The object of the present invention is achieved through the following technical scheme: A method for obtaining anisotropic parameters of a while-drilling VSP drive process, comprising the following steps:

[0007] S1. Collect basic seismic data: including CMP gathers, isotropic velocity field, anisotropic velocity field, anisotropic parameters, prestack time migration results, isotropic prestack depth migration results, anisotropic prestack depth migration results, and conduct quality evaluation and optimization on the collected data;

[0008] The quality evaluation method is: using the offset results to evaluate the quality of the collected data, and verifying whether the offset results are consistent with the final result data actually submitted;

[0009] The optimization method is: if there is inconsistency between the migration result and the final result data actually submitted, the data is optimized in combination with the latest geological knowledge to make the migration result of the data consistent with the final result data actually submitted, so that the data meets the VSP drive processing requirements;

[0010] S2. Collect VSP data;

[0011] S3. Carry out velocity field correction and optimization, use the collected drilling, logging and geological information as constraints, and re-optimize and correct the velocity field;

[0012] S4. Calculate the new anisotropy parameter δ new :

[0013]

[0014] Among them, δ old is the old anisotropy parameter that has been collected in the result data, v old is the anisotropic velocity collected in the result data, v new The new anisotropic velocity is obtained by iteration after re-optimizing the corrected velocity field;

[0015] S5, anisotropic parameter optimization and iteration, updating to obtain the ε body;

[0016] S6. Perform anisotropic depth migration using the updated anisotropic parameters to determine whether the CIP gather is flattened. If so, output the final imaging data volume. If not, return to S5.

[0017] The beneficial effects of the present invention are as follows: the present invention provides a method for obtaining anisotropic parameters for while-drilling VSP drive processing, which can make full use of the anisotropic parameters, anisotropic velocity and new iteration velocity of existing data to quickly and accurately calculate new anisotropic parameters; the anisotropic parameters in the basic data can be used to achieve accurate imaging of the while-drilling processing target area through rapid correction. The new anisotropic parameters can be used to provide decision support for optimizing well trajectories and proposing new target recommendations. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A flow chart of a method for obtaining anisotropic parameters of the present invention;

[0019] Figure 2 are the old anisotropic parameters that have been collected in the data of the present invention;

[0020] Figure 3 is the new anisotropy parameter of the present invention, DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the following takes the M well of the Tarim Oilfield as an example to clearly and completely describe the technical scheme in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0022] like Figure 1 As shown, a method for obtaining anisotropic parameters of a while-drilling VSP drive process of the present invention comprises the following steps:

[0023] S1. Collect 16km*16km basic seismic data around Well M: including CMP gathers, isotropic velocity field, anisotropic velocity field, anisotropic parameters, prestack time migration results, isotropic prestack depth migration results, anisotropic prestack depth migration results, and conduct quality evaluation and optimization on the collected data;

[0024] The quality evaluation method is: using the offset results to evaluate the quality of the collected data, and verifying whether the offset results are consistent with the final result data actually submitted;

[0025] The optimization method is: if there is inconsistency between the migration result and the final result data actually submitted, the data is optimized in combination with the latest geological knowledge to make the migration result of the data consistent with the final result data actually submitted, so that the data meets the VSP drive processing requirements;

[0026] S2, collect VSP data, and at the same time collect VSP acoustic logging curves, well velocity and other data of well M while drilling;

[0027] S3. Carry out velocity field correction and optimization, use the collected drilling, logging and geological information as constraints, and re-optimize and correct the velocity field;

[0028] Drilling information: well stratification data, cores, thin sections, etc. of known drillings.

[0029] Well logging information: various well logging curves, information such as sound wave velocity and rock density obtained by various well logging methods.

[0030] Geological information: underground stratum information, fault information, fracture information, lithology information, stratum velocity, stratum thickness and other information recognized by geologists.

[0031] The traditional anisotropy parameter δ estimation formula is:

[0032]

[0033] Among them, v iso represents the isotropic velocity, v ani Represents the anisotropic velocity. As mentioned above, although the traditional method for calculating anisotropic parameters can ensure the calculation accuracy, the calculation efficiency is not suitable for the VSP drive processing while drilling. In view of this, the present invention adopts a new calculation formula to calculate the anisotropic parameters. The specific method is: S4, calculate the new anisotropic parameter δ new :

[0034]

[0035] Among them, δ old are the old anisotropic parameters that have been collected in the results data, such as Figure 2 As shown; v old is the anisotropic velocity collected in the result data, v new The new anisotropic velocity is obtained by iteration after re-optimizing the corrected velocity field; the new anisotropic parameter δ new like Figure 3 As shown;

[0036] S5, anisotropic parameter optimization and iteration, updating to obtain the ε body;

[0037] S6. Perform anisotropic depth migration using the updated anisotropic parameters to determine whether the CIP gather is flattened. If so, output the final imaging data volume. If not, return to S5.

[0038] Based on the above anisotropic depth migration results, we can conduct results analysis and propose new target suggestions.

[0039] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A method for obtaining anisotropic parameters of a while-drilling VSP drive process, characterized in that: The following steps are involved: S1. Collect basic seismic data: including CMP gathers, isotropic velocity field, anisotropic velocity field, anisotropic parameters, prestack time migration results, isotropic prestack depth migration results, anisotropic prestack depth migration results, and conduct quality evaluation and optimization on the collected data; The quality evaluation method is: using the offset results to evaluate the quality of the collected data, and verifying whether the offset results are consistent with the final result data actually submitted; The optimization method is: if there is inconsistency between the migration result and the final result data actually submitted, the data is optimized in combination with the latest geological knowledge to make the migration result of the data consistent with the final result data actually submitted, so that the data meets the VSP drive processing requirements; S2. Collect VSP data; S3. Carry out velocity field correction and optimization, use the collected drilling, logging and geological information as constraints, and re-optimize and correct the velocity field; S4. Calculate the new anisotropy parameter δ new : Among them, δ old is the old anisotropy parameter that has been collected in the result data, v old is the anisotropic velocity collected in the result data, v new The new anisotropic velocity is obtained by iteration after re-optimizing the corrected velocity field; S5, anisotropic parameter optimization and iteration, updating to obtain the ε body; S6. Perform anisotropic depth migration using the updated anisotropic parameters to determine whether the CIP gather is flattened. If so, output the final imaging data volume. If not, return to S5.

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