Direct depth domain seismic longitudinal and transverse wave velocity ratio inversion method

Abstract

The invention provides a direct depth domain seismic longitudinal and transverse wave velocity ratio inversion method. According to the method, an SIRps equation about the seismic longitudinal and transverse wave velocity ratio of a partial angle superposition theory and a corresponding depth domain Bayesian seismic inversion method are established, inversion of parameters such as the seismic longitudinal and transverse wave velocity ratio is directly realized in a depth domain by utilizing depth domain seismic data, accumulative errors caused by domain conversion are reduced, the calculation efficiency is improved, and the method is suitable for large-scale popularization and application. The method has better robustness, is favorable for fully excavating effective information of depth domain seismic data, better describes distribution and characteristics of underground oil and gas reservoirs, and provides a more scientific and effective basis for decisions in geophysical exploration and development of oil and gas.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas seismic exploration, and in particular relates to a direct depth domain seismic longitudinal and transverse wave velocity ratio inversion method. Background Art

[0002] Depth domain migration technology has been widely used in the field of petroleum seismic exploration, and has become a key technical means to solve complex oil and gas reservoirs, accurately characterize fault structures, and carefully depict fluid characteristics. Thanks to its lateral variation in migration velocity, it is significantly superior to time domain migration technology in imaging complex geological structures and accurately identifying oil and gas. Therefore, depth domain seismic data usually has higher accuracy than time domain seismic data. However, the non-stationary nature of depth domain seismic data means that the traditional time domain inversion method based on the convolution model cannot be directly applied to depth domain seismic inversion. This limitation has hindered the application and development of depth domain seismic interpretation to a certain extent.

[0003] In the field of oil and gas seismic exploration, the seismic P-wave velocity ratio, that is, the ratio of the seismic P-wave velocity to the S-wave velocity, is a key parameter for formation description and reservoir prediction. It can effectively indicate the changes in formation lithology and realize the identification of different lithologies. The seismic P-wave velocity ratio can also be used as a fluid indicator factor to describe oil and gas reservoirs with development value. In actual oil and gas exploration and development, the combination of seismic P-wave velocity ratio and other elastic parameters is often used to further improve the accuracy of reservoir prediction and oil and gas identification.

[0004] Traditional prestack seismic inversion is usually an indirect method that inverts elastic parameters such as seismic P-wave and S-wave velocities from seismic data and then calculates the seismic P-wave and S-wave velocity ratio. However, this indirect method is prone to errors, and the accumulation of these errors in multiple steps may lead to large deviations in the final result, reducing the accuracy and reliability of the P-wave and S-wave velocity ratio parameters. In order to overcome this limitation, a method of directly inverting the seismic P-wave and S-wave velocity ratio is needed to reduce the above-mentioned cumulative errors, improve computational efficiency, increase the accuracy and reliability of the inversion results, and provide more reliable technical support for the detailed description and risk assessment of oil and gas reservoirs. With the continuous improvement of high-performance computing and the optimization of inversion algorithms, the method of directly inverting the P-wave and S-wave velocity ratio is expected to bring new breakthroughs in oil and gas exploration. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a method for directly inverting the seismic P-wave velocity ratio in the depth domain, and establishes the SI of the seismic P-wave velocity ratio based on the partial angle stacking theory. Rps Equation and the corresponding Bayesian seismic inversion method in depth domain.

[0006] The purpose of the present invention can be achieved through the following technical steps:

[0007] S1, seismic trace gathers with angle stacking of near, middle and far parts in input depth domain;

[0008] S2, input well logging data and layer information, and use the depth domain well-seismic calibration method to extract the seismic wavelets of the seismic gathers with angle stacking in the near, middle and far parts of the depth domain;

[0009] S3, establish the initial model of elastic parameters in depth domain;

[0010] S4, Establishment of partial angle stacking theory for the ratio of longitudinal and transverse velocity of earthquakes Rps equation:

[0011]

[0012] in,

[0013]

[0014] Among them, θ U and θ L Respectively represent the upper and lower limits of the earthquake incident angle range, R ps and R ps0 Respectively represent the seismic longitudinal and transverse wave velocity ratios and their mean values, V p and V p0 They represent the seismic P-wave velocity and its mean value, ρ and ρ0 represent the layer density and its mean value, represents the standard normalized impedance parameter of the equation, K represents the scaling factor of the P-wave velocity ratio of the upper and lower layers of the seismic reflection interface;

[0015] S5, build on SI Rps Bayesian seismic inversion method in depth domain based on equation:

[0016] The depth domain seismic gather S is expressed as the following matrix expression:

[0017]

[0018] Where W is the depth domain space-variant seismic wavelet matrix, D is the depth domain difference matrix, Noise is the depth domain noise matrix, A is the depth domain partial angle seismic forward operator, and X represents the matrix composed of the variables to be solved;

[0019] Let X obey the multivariate normal distribution N X (X0,Σ X ), there are X~N X (X0,Σ X ), its prior probability is:

[0020]

[0021] Among them, X0 is the mean of X, Σ X is the covariance matrix of X, Q1 is the number of elements of X, and T represents the matrix transpose operation;

[0022] A is used to construct the seismic forward modeling operator G for the near, middle and far angles in the depth domain. d is the matrix composed of the seismic gathers superimposed by the near, middle and far angles in the depth domain. d obeys the multivariate normal distribution N d (d0,Σ d ), there are d~N d (d0,Σ d ), the expression is as follows:

[0023]

[0024] Among them, the mean of d is d0=GX0, and the covariance matrix of d is Σ d =GΣ X G T +Σ e ,Σ e is the covariance matrix of the near, middle and far angular noise e, Q2 is the number of elements in d;

[0025] The maximum posterior distribution follows a multivariate normal distribution, X|d~N(μ X|d ,Σ X|d ), the expression is as follows:

[0026]

[0027] in,

[0028] μ X|d It is a matrix composed of the seismic longitudinal and transverse wave velocity ratios, seismic longitudinal wave velocity and density in the depth domain obtained by the inversion method of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions and embodiments of the present invention, the following briefly introduces the drawings required for use in the technical description and embodiments. The drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the subsequent specific implementation methods, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention.

[0030] Figure 1 It is a flow chart of the direct depth domain seismic longitudinal and transverse wave velocity ratio inversion method of the present invention.

[0031] Figure 2It is the seismic trace data of the near, middle and far parts superimposed at an angle used in the embodiment of the present invention. Each seismic profile data has 800 traces in total, the well is located at the 177th trace (marked with an inverted triangle in the figure), the black logging curve represents the logging P-wave velocity, and the target layer is marked by Layer1 and Layer2.

[0032] Figure 3 It is a seismic wavelet extracted from the seismic trace gathers with superimposed angles of near, middle and far parts in the depth domain in an embodiment of the present invention.

[0033] Figure 4 It is an initial model of elastic parameters in the depth domain established in the embodiment of the present invention, with a total of 800 lines. The inverted triangles in the figure mark the well locations. Figure 4 (a) is the ratio of longitudinal and transverse wave velocities. The black logging curve in the figure represents the ratio of longitudinal and transverse wave velocities of logging; Figure 4 (b) is the P-wave velocity. The black logging curve in the figure represents the P-wave velocity. Figure 4 (c) is density. The black logging curve in the figure represents the logging density.

[0034] Figure 5 1 is a seismic inversion result of elastic parameters in the depth domain according to an embodiment of the present invention, with a total of 800 traces. The inverted triangles in the figure mark the well locations. Figure 5 (a) is the inverted longitudinal and transverse wave velocity ratio. The black logging curve in the figure represents the longitudinal and transverse wave velocity ratio of the well logging; Figure 5 (b) is the inverted P-wave velocity. The black logging curve in the figure represents the logging P-wave velocity. Figure 5 (c) is the inverted density, and the black logging curve in the figure represents the logging density. DETAILED DESCRIPTION

[0035] In order to make the features and advantages of the present invention more obvious and easy to understand, the present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description. Figures 1 to 5 As shown, a direct depth domain seismic longitudinal and transverse wave velocity ratio inversion method includes the following steps:

[0036] S1, input the seismic traces of the near, middle and far parts of the depth domain, such as Figure 2 As shown in FIG. 1 , these seismic gathers are completed by stacking seismic data in the angle ranges of 3° to 12°, 15° to 24°, and 27° to 36°.

[0037] S2, input the logging data and the layer information, and use the depth domain well-seismic calibration method of the present invention to extract the seismic wavelets of the seismic trace gathers with angle stacking of the near, middle and far parts in the depth domain, such as Figure 3 As shown;

[0038] S3, establish the initial model of depth domain elastic parameters, such as Figure 4 As shown;

[0039] S4, Establishment of partial angle stacking theory for the ratio of longitudinal and transverse velocity of earthquakes Rps equation:

[0040]

[0041] in,

[0042]

[0043] Among them, θ U and θ L Respectively represent the upper and lower limits of the earthquake incident angle range, R ps and R ps0 Respectively represent the seismic longitudinal and transverse wave velocity ratios and their mean values, V p and V p0 They represent the seismic P-wave velocity and its mean value, ρ and ρ0 represent the layer density and its mean value, represents the standard normalized impedance parameter of the equation, K represents the scaling factor of the P-wave velocity ratio of the upper and lower layers of the seismic reflection interface;

[0044] S5, build on SI Rps Bayesian seismic inversion method in depth domain based on equation:

[0045] The depth domain seismic gather S is expressed as the following matrix expression:

[0046]

[0047] Where W is the depth domain space-variant seismic wavelet matrix, D is the depth domain difference matrix, Noise is the depth domain noise matrix, A is the depth domain partial angle seismic forward operator, and X represents the matrix composed of the variables to be solved;

[0048] Let X obey the multivariate normal distribution N X (X0,Σ X ), there are X~N X (X0,Σ X ), its prior probability is:

[0049]

[0050] Among them, X0 is the mean of X, Σ X is the covariance matrix of X, Q1 is the number of elements of X, and T represents the matrix transpose operation;

[0051] A is used to construct the seismic forward modeling operator G for the near, middle and far angles in the depth domain. d is the matrix composed of the seismic gathers superimposed by the near, middle and far angles in the depth domain. d obeys the multivariate normal distribution Nd (d0,Σ d ), there are d~N d (d0,Σ d ), the expression is as follows:

[0052]

[0053] Among them, the mean of d is d0=GX0, and the covariance matrix of d is Σ d =GΣ X G T +Σ e ,Σ e is the covariance matrix of the near, middle and far angular noise e, Q2 is the number of elements in d;

[0054] The maximum posterior distribution follows a multivariate normal distribution, X|d~N(μ X|d ,Σ X|d ), the expression is as follows:

[0055]

[0056] in,

[0057] μ X|d is a matrix composed of the depth domain seismic longitudinal and transverse wave velocity ratios, seismic longitudinal wave velocity and density obtained by the inversion method of the present invention, such as Figure 5 shown.

[0058] from Figure 5 It can be seen from the seismic inversion results of the depth domain elastic parameters that each elastic parameter well reflects the spatial position and lateral changes of different lithological strata, and the inversion results are in good agreement with the logging curves, which proves that the method of the present invention is accurate and reliable.

[0059] The advantages of the method of the present invention are: (1) by using deep-domain seismic data, the inversion of seismic parameters such as the longitudinal and transverse wave velocity ratio is directly realized in the depth domain, which reduces the seismic data conversion operations between different domains and improves the calculation efficiency; (2) compared with the inversion of separate seismic longitudinal or transverse wave velocities, the inversion of the seismic longitudinal and transverse wave velocity ratio is less sensitive to noise and interference, and is therefore suitable for parameter inversion of actual deep-domain seismic data and has better robustness; (3) direct inversion of the longitudinal and transverse wave velocity ratio of seismic in the depth domain is conducive to better predicting the distribution and characteristics of underground oil and gas reservoirs, and provides a more scientific and effective basis for decision-making in oil and gas geophysical exploration and development.

[0060] The above embodiments are only used to illustrate the present invention, wherein the various implementation steps of the method can be changed, and any equivalent transformations and improvements based on the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. The direct depth domain seismic P-wave velocity ratio inversion method mainly includes the following steps: S1, seismic trace gathers with angle stacking of near, middle and far parts in input depth domain; S2, input well logging data and layer information, and use the depth domain well-seismic calibration method to extract the seismic wavelets of the seismic gathers with angle stacking in the near, middle and far parts of the depth domain; S3, establish the initial model of elastic parameters in depth domain; S4, Establishment of partial angle stacking theory for the ratio of longitudinal and transverse velocity of earthquakes Rps equation: ， in, ， in, and They represent the upper and lower limits of the earthquake incident angle range, and They represent the seismic longitudinal and transverse wave velocity ratios and their means, respectively. and They represent the seismic P-wave velocity and its mean value in the layer, and represent the layer density and its mean, respectively. represents the standard normalized impedance parameter of the equation, It represents the scaling factor of the P-wave velocity ratio between the upper and lower layers of the seismic reflection interface; S5, build on SI Rps Bayesian seismic inversion method in depth domain based on equation: Depth Domain Seismic Gathers It is represented by the following matrix expression: ， in, is the depth-domain space-variant seismic wavelet matrix, is the depth domain difference matrix, is the depth domain noise matrix, is the partial angle seismic forward modeling operator in the depth domain, A matrix representing the variables to be solved; make Follow multivariate normal distribution ,have , its prior probability is: ， in, for The mean of for The covariance matrix of for The number of elements of , T represents the matrix transpose operation; use Constructing partial angle seismic forward modeling operators for near, medium and far depth domain , It is a matrix composed of seismic trace gathers with stacked angles at the near, middle and far parts of the depth domain; Follow multivariate normal distribution ,have , the expression is as follows: ， in, The mean , The covariance matrix of , The near, middle and far angle noise The covariance matrix of for The number of elements of ; The maximum posterior distribution follows a multivariate normal distribution. , the expression is as follows: ， in, ; It is a matrix composed of the seismic longitudinal and transverse wave velocity ratios, seismic longitudinal wave velocity and density in the depth domain obtained by the inversion method of the present invention.

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