CN112130211A - Method and system for calculating Gassmann fluid items - Google Patents
Method and system for calculating Gassmann fluid items Download PDFInfo
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Abstract
The invention discloses a method and a system for calculating Gassmann fluid items, which comprise the following steps: s1, acquiring stacked seismic data volumes of different scales and different angles; s2, establishing a fluid elastic impedance low-frequency model of the first angle to the third angle; s3, gradually carrying out fluid elastic impedance inversion from a first angle to a third angle according to the sequence from the first angle to the third angle, constraining the optimization process of inversion from the second angle by taking the inversion result from the first angle as a prior model, and constraining the optimization process from the third angle by taking the inversion result from the second angle as the prior model, and finally obtaining the fluid elastic impedance inversion results from the first angle to the third angle; s4 carries out logarithmic transformation on the inversion results of the elastic impedance of the fluids of the first to third angles obtained in the step S3, constructs a solving equation of the Gassmann fluid item by combining logging statistical information, solves an equation set and obtains the Gassmann fluid item of the seismic scale.
Description
Technical Field
The invention relates to a method and a system for calculating Gassmann fluid items based on a scale-by-scale progressive inversion strategy, and belongs to the technical field of geophysical exploration.
Background
With the development and progress of rock physics theory, seismic processing technology and pre-stack seismic inversion algorithm, reservoir hydrocarbon detection by using elastic parameters has become a common method in the oil and gas industry. In practical production application, in order to improve the accuracy of hydrocarbon detection, how to construct elastic parameters sensitive to the types of underground pore medium fluids and stably and reliably calculate the elastic parameters are always the research directions of researchers.
The Gassmann fluid item is an elastic parameter deduced by Russell et al in 2006 based on a Biot-Gassmann equation, and the elastic parameter can well reduce hydrocarbon detection artifacts caused by the porosity parameter of the underground pore medium, thereby indicating the type of the underground pore medium pore fluid more directly and having sensitive reservoir hydrocarbon identification sensitivity. At present, the related industry mostly uses prestack earthquake as a main body, uses known geological rules and well logging data as prior constraints, and adopts a fluid elastic impedance inversion technology to calculate Gassmann fluid items. However, as the underground target is more and more complex, the conventional prestack inversion method is difficult to meet the requirement of actual production, especially for oil and gas reservoirs of hidden lithology, deep reservoirs, river-delta facies thin reservoirs and other types, the thickness of the reservoirs of the types is generally smaller than the seismic resolution of a target interval, and the spatial heterogeneity is relatively strong, and in addition, the calculation of a global optimal solution is further influenced by the ill-posed property of the conventional inversion method, so that the hydrocarbon detection requirement of the complex geological target is difficult to meet by using Gassmann fluid parameters calculated by the conventional inversion method, and further the evaluation quality of the reservoirs is influenced.
Disclosure of Invention
In view of the above problems, the present invention provides a method and system for calculating Gassmann fluid items based on a scale-by-scale progressive inversion strategy.
In order to achieve the above object, the present invention adopts the following technical solution, a method for calculating a Gassmann fluid item, comprising the steps of,
s1, acquiring stacked seismic data volumes of different scales and different angles, wherein the different scales comprise a first scale, a second scale and a third scale which are sequentially decreased, and the different angles comprise a first angle, a second angle and a third angle which are sequentially increased;
s2, establishing a fluid elastic impedance low-frequency model of the first angle to the third angle;
s3, gradually carrying out fluid elastic impedance inversion from a first angle to a third angle according to the sequence from the first angle to the third angle, and constraining the optimization process of inversion of the second angle by taking the inversion result of the first angle as a prior model, and constraining the optimization process of the third angle by taking the inversion result of the second angle as the prior model, and finally obtaining the fluid elastic impedance inversion results from the first angle to the third angle;
s4, carrying out logarithmic transformation on the inversion results of the elastic impedance of the fluids of the first to third angles obtained in the step S3, constructing a solving equation of a Gassmann fluid item by combining logging statistical information, solving an equation set and obtaining the Gassmann fluid item of the seismic scale
The solution equation for constructing the Gassmann fluid term is as follows:
in the formula, EI represents the fluid elastic impedance; t represents time; theta1Represents a first angle; theta2Represents a second angle; theta3Represents a third angle;
θ represents an incident angle;
representing the square of the velocity ratio of the longitudinal wave and the transverse wave of the saturated fluid rock;
represents the square of the dry rock compressional-shear velocity ratio; f. mu and rho respectively represent Gassmann fluid item, shear modulus and density parameters; f. of0、μ0And ρ0Defined as the average of the Gassmann fluid term, shear modulus and density parameters, respectively; EI (El)0Is the normalization factor.
Further, in step S1, acquiring stacked seismic data volumes of different scales and different angles, the specific process includes:
s11, performing explanatory preprocessing on the acquired pre-stack seismic angle gather covering the research area;
s12, performing sub-angle stacking processing on the pre-stack seismic angle gather in the step S11 to obtain stacked seismic data of first to third angles;
and S13, carrying out frequency division processing on the stacked seismic data of the first to third angles in the step S12 based on the frequency spectrum analysis result of the target interval beside the well to obtain stacked seismic data volumes of the first to third angles in the first to third scales.
Further, in step S12, the sub-angle superimposing process includes the steps of:
s121, acquiring stratum velocity model data of a research area;
s122, converting the prestack seismic angle gather from a time domain to a depth domain based on a stratum velocity model, converting the offset and the incident angle by using the depth of a target layer and the length of the maximum offset, and taking the conversion as the tangent value of the incident angle according to the ratio of half of the length of the maximum offset to the target depth;
s123, comprehensively analyzing the theoretical maximum incident angle, the coverage times and the factors of multiple residual of a near channel, determining the effective incident angle range interval of the angle seismic gather, trisecting the effective incident angle interval to form a first incident angle bisecting range, a second incident angle bisecting range and a third incident angle bisecting range, and determining the median of the three bisecting ranges as a first angle, a second angle and a third angle;
and S124, correspondingly stacking the pre-stack seismic angle gathers in the first incidence angle equal-dividing range, correspondingly stacking the pre-stack seismic angle gathers in the second incidence angle equal-dividing range, and correspondingly stacking the pre-stack seismic angle gathers in the third incidence angle equal-dividing range to form stacked seismic data at first to third angles.
Further, in step S13, the frequency division processing procedure is as follows:
s131, based on the seismic frequency spectrum analysis result of the target interval beside the well, determining effective frequency bandwidth and dominant frequency, wherein the median frequency of low frequency and dominant frequency of the effective frequency bandwidth is taken as a first scale, the dominant frequency is taken as a second scale, and the median frequency of high frequency and dominant frequency of the effective frequency bandwidth is taken as a third scale;
s132, frequency division processing is carried out on the stacked seismic data of the first to third angles by using a matching pursuit time-frequency decomposition method, and first to third scales of seismic data of the stacked seismic data of the first to third angles are obtained and are respectively first scale first angle seismic data, second scale first angle seismic data, third scale first angle seismic data, first scale second angle seismic data, second scale second angle seismic data, third scale second angle seismic data, first scale third angle seismic data, second scale third angle seismic data and third scale third angle seismic data.
Further, in step S2, a low-frequency model of the fluid elastic impedance at the first to third angles is established, which includes the following steps:
s21, calculating the elastic impedance of the fluid in the first to third angles in the step S1 based on the obtained logging data;
s22, under the restraint of a target interval horizon frame, performing interpolation calculation on the fluid elastic impedance parameters calculated in the step S21 by adopting a global Krigin interpolation algorithm to generate fluid elastic impedance model data volumes of first to third angles;
and S23, filtering the obtained fluid elastic impedance model data volumes of the first to third angles to obtain fluid elastic impedance low-frequency models of the first to third angles required by inversion.
Further, in step S21, the calculation formula of the fluid elastic impedance is as follows:
further, in step S3, the fluid elastic impedance inversion at the first to third angles is performed gradually in the order from the first to third scales, and the specific process is as follows:
s31, performing fluid elastic impedance inversion of the stacked seismic data of the first to third angles of the first scale
S311, based on the stacked seismic data of the first to third angles of the first scale, focusing a target interval to extract first to third angle wavelets of the first scale;
s312, taking the fluid elastic impedance low-frequency models of the first to third angles calculated in the step S2 as constraints, and performing fluid elastic impedance inversion based on the first to third angle wavelet data of the first scale to obtain fluid elastic impedance data volumes of the first to third angles of the first scale;
s32, performing fluid elastic impedance inversion of the stacked seismic data of the first to third angles of the second scale
S321, based on the first to third angle superposition seismic data of the second scale, focusing a target interval to extract first to third angle wavelets of the second scale;
s322, acquiring the fluid elastic impedance data volumes of the first scale and the third angle in the step S312, and performing low-pass filtering to use the data volumes as low-frequency models required by inversion of the fluid elastic impedance of the first scale and the third angle in the second scale;
s323, taking the low-frequency model in the step S322 as a constraint, and performing fluid elastic impedance inversion based on the wavelet data of the first to third angles of the second scale to obtain a fluid elastic impedance data volume of the first to third angles of the second scale;
s33, performing fluid elastic impedance inversion of the stacked seismic data of the first to third angles of the third scale
S331, based on the first to third angle superposition seismic data of the third scale, focusing a target interval and extracting first to third angle wavelets of the third scale;
s332, acquiring the fluid elastic impedance data volumes of the first angle to the third angle of the second scale in the step 323, and performing low-pass filtering to use the data volumes as low-frequency models required by inversion of the fluid elastic impedance of the first angle to the third angle of the third scale;
s333, taking the low-frequency model in the step S332 as a constraint, and performing fluid elastic impedance inversion based on the wavelet data of the first to third angles in the third scale to obtain fluid elastic impedance data volumes of the first to third angles in the third scale, wherein the fluid elastic impedance data volumes are used as final fluid elastic impedance inversion results of the first to third angles.
Further, in step S13, the interval spectrum analysis process at the target site beside the well is as follows:
i) acquiring the time-depth relation between the post-stack seismic data and the well drilling;
ii) based on the post-stack seismic data, focusing the target interval to extract statistical seismic wavelets and calculating a synthetic seismic record;
iii) carrying out time depth calibration, and defining seismic response characteristics and time range of the target interval;
iv) performing seismic spectrum analysis on the target interval based on the post-stack seismic data.
Further, in step S22, the horizon frame building process of the target interval is as follows:
I) acquiring the time-depth relation between the post-stack seismic data and the well drilling;
II) focusing the target interval to extract statistical seismic wavelets based on the post-stack seismic data, and calculating a synthetic seismic record;
III) carrying out time-depth calibration, and determining seismic response characteristics and time ranges of the target interval;
IV) focusing the target layer section to start seismic structure interpretation based on the time-depth calibration result of the step III) to obtain a layer position representing the top surface and the bottom surface of the target layer;
v) constructing a horizon frame by utilizing the top surface and the bottom surface of the destination layer explained in the step IV).
Additionally, the present invention also provides a system for calculating Gassmann fluid items, comprising:
a data input module configured to acquire first to third angle stack seismic data volumes at first to third scales;
a low-frequency model building module configured to build a fluid elastic impedance low-frequency model of the first to third angles participating in the inversion;
the scale-by-scale inversion module is configured to gradually perform fluid elastic impedance inversion from a first angle to a third angle according to the sequence from the first scale to the third scale, and constrain an optimization process of second scale inversion by taking a first scale inversion result as a prior model, constrain an optimization process of third scale inversion by taking a second scale inversion result as the prior model, and finally obtain fluid elastic impedance inversion results from the first angle to the third angle;
and the data output module is configured to perform logarithmic transformation on the obtained fluid elastic impedance data of the first angle to the third angle, construct a solving equation of the Gassmann fluid item by combining logging statistical information, and obtain final parameters of the Gassmann fluid item.
By adopting the technical scheme, the invention has the following advantages: 1. according to the method, a scale-by-scale inversion strategy from the first scale to the third scale is adopted, the effective bandwidth information of the pre-stack earthquake is fully utilized to represent the underground target, the using capacity of high-frequency effective information of the earthquake is further increased, compared with a conventional earthquake inversion method, an inversion result has higher resolution, and the result is more suitable for evaluation of a complex geological target;
2. according to the method, the inversion result of the fluid elastic impedance is used as prior model information to constrain a secondary inversion optimization process, and the influence of a local minimum value is reduced through segmented progressive optimization of different scales, so that the result is closer to a global optimal solution, and the inversion result can better accord with the actual condition of an underground target;
3. according to the invention, the fluid elastic impedance formula directly containing the Gassmann fluid item is adopted in the solving process of the Gassmann fluid item, so that the calculation error caused by the fact that the longitudinal and transverse wave speeds and the density are firstly obtained by a conventional fluid elastic impedance inversion method and then the Gassmann fluid item is indirectly calculated is avoided, and the calculation precision of the Gassmann fluid item is improved.
In conclusion, the method can improve the hydrocarbon detection reliability of the complex geological target, particularly the thin reservoir, and provides technical support for solving the problem of oil-gas identification of the complex reservoir.
Drawings
FIG. 1 is a block flow diagram of the present invention;
FIG. 2 is a block diagram of a process for obtaining sub-scale seismic data in accordance with the present invention;
FIG. 3 is a block diagram of a process for building a low frequency model according to the present invention;
FIG. 4 is a block flow diagram of the fluid elastic impedance inversion of the present invention;
FIG. 5 is a block flow diagram of Gassmann fluid item calculation in accordance with the present invention;
FIG. 6 is a schematic flow diagram of a Gassmann fluid computing system of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and examples. It is to be understood, however, that the drawings are provided solely for the purposes of promoting an understanding of the invention and that they are not to be construed as limiting the invention.
As shown in fig. 1, the present invention provides a method for calculating Gassmann fluid items, comprising the steps of:
as shown in fig. 2, S1, acquiring stacked seismic data volumes at different angles and with different scales, where the different scales include three scales decreasing sequentially, and for convenience of description, the three scales are referred to as a first scale, a second scale, and a third scale, the different angles include three angles increasing sequentially, and the three angles are referred to as a first angle, a second angle, and a third angle, and the specific process is as follows:
s11, performing explanatory preprocessing on the acquired pre-stack seismic angle gather covering the research area;
s12, performing sub-angle stacking processing on the pre-stack seismic angle gather in the step S11 to obtain stacked seismic data of first to third angles;
and S13, carrying out frequency division processing on the stacked seismic data of the first to third angles in the step S12 based on the frequency spectrum analysis result of the target interval beside the well to obtain stacked seismic data volumes of the first to third angles in the first to third scales.
As shown in FIG. 3, S2, establishing the low frequency model of the fluid elastic impedance at the first to third angles
S21, obtaining logging data such as logging curves and logging interpretation results, and calculating the elastic impedance of the fluid in the first to third angles in the step S1 based on the logging data;
it should be noted that the fluid elastic impedance is an elastic impedance expression form containing the parameters of the Gassmann fluid item, shear modulus and density, compared with the elastic impedance expressed by the conventional parameters of longitudinal wave velocity, transverse wave velocity and density, the inversion of the Gassmann fluid item can be directly realized by using the fluid elastic impedance, and compared with the conventional method of inverting the parameters of longitudinal wave velocity, transverse wave velocity and density and then calculating the Gassmann fluid item by algebraic operation, the method has higher precision, so the fluid elastic impedance is necessary to be used.
The calculation formula of the fluid elastic impedance is as follows:
in the formula, EI represents the fluid elastic impedance; θ represents an incident angle;
representing the square of the velocity ratio of the longitudinal wave and the transverse wave of the saturated fluid rock;
represents the square of the dry rock compressional-shear velocity ratio;
f. mu and rho respectively represent Gassmann fluid item, shear modulus and density parameters; f. of0、μ0And ρ0Defined as the average of the Gassmann fluid term, shear modulus and density parameters, respectively; EI (El)0Is the normalization factor.
S22, under the restraint of a target interval horizon frame, performing interpolation calculation on the fluid elastic impedance parameters calculated in the step S21 by adopting a global Krigin interpolation algorithm to generate fluid elastic impedance model data volumes of first to third angles;
s23, filtering the obtained fluid elastic impedance model data volume of the first to third angles to obtain a fluid elastic impedance low-frequency model of the first to third angles required by inversion;
and designing a 0-10Hz low-pass filter, and carrying out filtering processing on the fluid elastic impedance model data bodies at the first to third angles to obtain a low-frequency model participating in inversion.
As shown in fig. 4, S3, gradually performing the fluid elastic impedance inversion of the first to third angles in the order from the first to third scales
The method comprises the steps of firstly extracting first to third angle stack seismic data wavelets of first to third scales, then carrying out fluid elastic impedance inversion according to the sequence of gradual progression from the first scale, the second scale and the third scale, namely carrying out fluid elastic impedance inversion of the first to third angles of the stack seismic data of the first scale, then carrying out fluid elastic impedance inversion of the first to third angles of the stack seismic data of the second scale, and finally carrying out fluid elastic impedance inversion of the first to third angles of the stack seismic data of the third scale, wherein the first scale inversion result is used as a prior model to constrain the optimization process of the second scale inversion, the second scale inversion result is used as the prior model to constrain the optimization process of the third scale, and finally obtaining the fluid elastic impedance inversion results of the first to third angles.
As shown in fig. 5, S4, performing logarithmic transformation on the inversion results of the elastic impedance of the fluids of the first to third angles obtained in step S3, constructing a solution equation of the Gassmann fluid item by combining the logging statistical information, solving the equation set, and obtaining the Gassmann fluid item of the seismic scale
The solution equation for constructing the Gassmann fluid term is as follows:
wherein t represents time; theta1Representing a first angle of incidence (i.e., a first angle); theta2Representing a second angle of incidence (i.e., a second angle); theta3Representing a third angle of incidence (i.e., a third angle).
Further, in step S12, performing sub-angle stacking processing on the pre-stack seismic angle gather in step S11 to obtain first to third angle stacked seismic data, where the specific process includes:
s121, acquiring stratum velocity model data of a research area;
s122, converting the prestack seismic angle gather from a time domain to a depth domain based on a stratum velocity model, converting the offset and the incident angle by using the depth of a target layer and the length of the maximum offset, and taking the conversion as the tangent value of the incident angle according to the ratio of half of the length of the maximum offset to the target depth;
s123, comprehensively analyzing multiple factors such as the maximum incident angle, the number of times of coverage and multiple wave residues of a near channel of a theory, determining an effective incident angle range interval of the angle seismic gather, trisecting the effective incident angle interval to form a first incident angle bisecting range, a second incident angle bisecting range and a third incident angle bisecting range, and determining the median of the three bisecting ranges as a first angle (namely, a first incident angle), a second angle (namely, a second incident angle) and a third angle (namely, a third incident angle);
and S124, correspondingly stacking the pre-stack seismic angle gathers in the first incidence angle equal-dividing range, correspondingly stacking the pre-stack seismic angle gathers in the second incidence angle equal-dividing range, and correspondingly stacking the pre-stack seismic angle gathers in the third incidence angle equal-dividing range to form stacked seismic data at first to third angles.
Further, in step S13, frequency division processing is performed on the stacked seismic data at the first to third angles in step S12 based on the analysis result of the spectrum of the target interval beside the well, and the frequency division processing procedure is as follows:
s131, based on the seismic spectrum analysis result of the well-side target interval, defining effective frequency bandwidth and dominant frequency, wherein the median frequency of the low frequency of the effective frequency bandwidth and the dominant frequency (namely, half of the sum of the low frequency of the effective frequency bandwidth and the dominant frequency) is taken as a first scale, the dominant frequency is taken as a second scale, and the median frequency of the high frequency of the effective frequency bandwidth and the dominant frequency (namely, half of the sum of the high frequency of the effective frequency bandwidth and the dominant frequency) is taken as a third scale;
s132, frequency division processing is carried out on the stacked seismic data of the first to third angles by using a matching pursuit time-frequency decomposition method, and first to third seismic data of the stacked seismic data of the first to third angles are obtained and are respectively first-scale first-angle seismic data, second-scale first-angle seismic data, third-scale first-angle seismic data, first-scale second-angle seismic data, second-scale second-angle seismic data, third-scale second-angle seismic data, first-scale third-angle seismic data, second-scale third-angle seismic data and third-scale third-angle seismic data.
Further, in step S13, the process of analyzing the spectrum of the target interval beside the well is as follows:
i) acquiring the time-depth relation between the post-stack seismic data and the well drilling;
ii) based on the post-stack seismic data, focusing the target interval to extract statistical seismic wavelets and calculating a synthetic seismic record;
iii) carrying out time depth calibration, and defining seismic response characteristics and time range of the target interval;
iv) performing seismic spectrum analysis on the target interval based on the post-stack seismic data.
Further, in step S22, the process of building the horizon frame of the target interval is as follows:
I) acquiring the time-depth relation between the post-stack seismic data and the well drilling;
II) focusing the target interval to extract statistical seismic wavelets based on the post-stack seismic data, and calculating a synthetic seismic record;
III) carrying out time-depth calibration, and determining seismic response characteristics and time ranges of the target interval;
IV) focusing the target layer section to start seismic structure interpretation based on the time-depth calibration result of the step III) to obtain a layer position representing the top surface and the bottom surface of the target layer;
v) constructing a horizon frame by utilizing the top surface and the bottom surface of the destination layer explained in the step IV).
Further, in step S3, the fluid elastic impedance inversion at the first to third angles is performed gradually in the order from the first to third scales, and the specific process is as follows:
s31, performing fluid elastic impedance inversion of the stacked seismic data of the first to third angles of the first scale
S311, based on the stacked seismic data of the first to third angles of the first scale, focusing a target interval to extract first to third angle wavelets of the first scale;
s312, taking the fluid elastic impedance low-frequency models of the first to third angles calculated in the step S2 as constraints, and performing fluid elastic impedance inversion based on the first to third angle wavelet data of the first scale to obtain fluid elastic impedance data volumes of the first to third angles of the first scale;
s32, performing fluid elastic impedance inversion of the stacked seismic data of the first to third angles of the second scale
S321, based on the first to third angle superposition seismic data of the second scale, focusing a target interval to extract first to third angle wavelets of the second scale;
s322, acquiring the fluid elastic impedance data volumes of the first scale and the third angle in the step S312, and performing low-pass filtering to use the data volumes as low-frequency models required by inversion of the fluid elastic impedance of the first scale and the third angle in the second scale;
s323, taking the low-frequency model in the step S322 as a constraint, and performing fluid elastic impedance inversion based on the wavelet data of the first to third angles of the second scale to obtain a fluid elastic impedance data volume of the first to third angles of the second scale;
s33, performing fluid elastic impedance inversion of the stacked seismic data of the first to third angles of the third scale
S331, based on the first to third angle superposition seismic data of the third scale, focusing a target interval and extracting first to third angle wavelets of the third scale;
s332, acquiring the fluid elastic impedance data volumes of the first angle to the third angle of the second scale in the step 323, and performing low-pass filtering to use the data volumes as low-frequency models required by inversion of the fluid elastic impedance of the first angle to the third angle of the third scale;
s333, taking the low-frequency model in the step S332 as a constraint, and performing fluid elastic impedance inversion based on the wavelet data of the first to third angles in the third scale to obtain fluid elastic impedance data volumes of the first to third angles in the third scale, wherein the fluid elastic impedance data volumes are used as final fluid elastic impedance inversion results of the first to third angles.
It should be noted that the conventional elastic impedance is not inverted step by step according to the scale, the inversion result is mainly the main frequency information of the seismic data, and the utilization rate of the seismic high-frequency information is insufficient.
As shown in fig. 6, based on the method for calculating the Gassmann fluid items based on the scale-by-scale progressive inversion strategy in any of the above embodiments, the present invention further provides a system for calculating the Gassmann fluid items, including:
the data input module is configured to perform explanatory preprocessing on the acquired pre-stack seismic angle gathers covering the research area, and perform angle-dividing stacking processing and frequency-dividing processing on the angle gathers subjected to the explanatory preprocessing on the basis of a stratum velocity model and a well-side target interval spectrum analysis result to obtain first to third angle stacking seismic data volumes of first to third scales;
the low-frequency model establishing module is configured to calculate fluid elastic impedance parameters of first to third angles based on logging information, perform interpolation calculation on the fluid elastic impedance parameters by combining a layer position interpretation result and a global kriging interpolation algorithm, and obtain fluid elastic impedance low-frequency models of the first to third angles participating in inversion through low-pass filtering processing interpolation calculation to obtain fluid elastic impedance model data volumes of the first to third angles;
the scale-by-scale inversion module is configured to extract first to third-degree seismic wavelets of first to third scales from first to third-degree stacked seismic data volumes of the first to third scales, and perform fluid elastic impedance inversion according to a progressive sequence from the first scale to the third scale to obtain fluid elastic impedance data of first to third angles;
and the data output module is configured to perform logarithmic transformation on the obtained fluid elastic impedance data of the first angle to the third angle, construct a solving equation of the Gassmann fluid item by combining logging statistical information, and obtain final parameters of the Gassmann fluid item.
The present invention has been described with reference to the above embodiments, and the structure, arrangement, and connection of the respective members may be changed. On the basis of the technical scheme of the invention, the improvement or equivalent transformation of the individual components according to the principle of the invention is not excluded from the protection scope of the invention.
Claims (10)
1. A method of calculating Gassmann fluid items, comprising the steps of,
s1, acquiring stacked seismic data volumes of different scales and different angles, wherein the different scales comprise a first scale, a second scale and a third scale which are sequentially decreased, and the different angles comprise a first angle, a second angle and a third angle which are sequentially increased;
s2, establishing a fluid elastic impedance low-frequency model of the first angle to the third angle;
s3, gradually carrying out fluid elastic impedance inversion from a first angle to a third angle according to the sequence from the first angle to the third angle, and constraining the optimization process of inversion of the second angle by taking the inversion result of the first angle as a prior model, and constraining the optimization process of the third angle by taking the inversion result of the second angle as the prior model, and finally obtaining the fluid elastic impedance inversion results from the first angle to the third angle;
s4, carrying out logarithmic transformation on the inversion results of the elastic impedance of the fluids of the first to third angles obtained in the step S3, constructing a solving equation of a Gassmann fluid item by combining logging statistical information, solving an equation set and obtaining the Gassmann fluid item of the seismic scale
The solution equation for constructing the Gassmann fluid term is as follows:
in the formula, EI represents the fluid elastic impedance; t represents time; theta1Represents a first angle; theta2Represents a second angle; theta3Represents a third angle;
θ represents an incident angle;
representing the square of the velocity ratio of the longitudinal wave and the transverse wave of the saturated fluid rock;
represents the square of the dry rock compressional-shear velocity ratio; f. mu and rho respectively represent Gassmann fluid item, shear modulus and density parameters; f. of0、μ0And ρ0Defined as the average of the Gassmann fluid term, shear modulus and density parameters, respectively; EI (El)0Is the normalization factor.
2. The method of calculating Gassmann fluid items of claim 1,
in step S1, acquiring stacked seismic data volumes at different angles and with different scales, the specific process includes:
s11, performing explanatory preprocessing on the acquired pre-stack seismic angle gather covering the research area;
s12, performing sub-angle stacking processing on the pre-stack seismic angle gather in the step S11 to obtain stacked seismic data of first to third angles;
and S13, carrying out frequency division processing on the stacked seismic data of the first to third angles in the step S12 based on the frequency spectrum analysis result of the target interval beside the well to obtain stacked seismic data volumes of the first to third angles in the first to third scales.
3. The method of claim 2, wherein the angular overlap process of step S12 comprises the steps of:
s121, acquiring stratum velocity model data of a research area;
s122, converting the prestack seismic angle gather from a time domain to a depth domain based on a stratum velocity model, converting the offset and the incident angle by using the depth of a target layer and the length of the maximum offset, and taking the conversion as the tangent value of the incident angle according to the ratio of half of the length of the maximum offset to the target depth;
s123, comprehensively analyzing the theoretical maximum incident angle, the coverage times and the factors of multiple residual of a near channel, determining the effective incident angle range interval of the angle seismic gather, trisecting the effective incident angle interval to form a first incident angle bisecting range, a second incident angle bisecting range and a third incident angle bisecting range, and determining the median of the three bisecting ranges as a first angle, a second angle and a third angle;
and S124, correspondingly stacking the pre-stack seismic angle gathers in the first incidence angle equal-dividing range, correspondingly stacking the pre-stack seismic angle gathers in the second incidence angle equal-dividing range, and correspondingly stacking the pre-stack seismic angle gathers in the third incidence angle equal-dividing range to form stacked seismic data at first to third angles.
4. The method of calculating the Gassmann fluid item of claim 2 wherein in step S13, the frequency division process is as follows:
s131, based on the seismic frequency spectrum analysis result of the target interval beside the well, determining effective frequency bandwidth and dominant frequency, wherein the median frequency of low frequency and dominant frequency of the effective frequency bandwidth is taken as a first scale, the dominant frequency is taken as a second scale, and the median frequency of high frequency and dominant frequency of the effective frequency bandwidth is taken as a third scale;
s132, frequency division processing is carried out on the stacked seismic data of the first to third angles by using a matching pursuit time-frequency decomposition method, and first to third scales of seismic data of the stacked seismic data of the first to third angles are obtained and are respectively first scale first angle seismic data, second scale first angle seismic data, third scale first angle seismic data, first scale second angle seismic data, second scale second angle seismic data, third scale second angle seismic data, first scale third angle seismic data, second scale third angle seismic data and third scale third angle seismic data.
5. The method of claim 1, wherein in step S2, the fluid elastic impedance low frequency models of the first to third angles are established as follows:
s21, calculating the elastic impedance of the fluid in the first to third angles in the step S1 based on the obtained logging data;
s22, under the restraint of a target interval horizon frame, performing interpolation calculation on the fluid elastic impedance parameters calculated in the step S21 by adopting a global Krigin interpolation algorithm to generate fluid elastic impedance model data volumes of first to third angles;
and S23, filtering the obtained fluid elastic impedance model data volumes of the first to third angles to obtain fluid elastic impedance low-frequency models of the first to third angles required by inversion.
6. The method of calculating a Gassmann fluid term according to claim 5 wherein the fluid elastic impedance is calculated in step S21 as follows:
7. the method of claim 1, wherein in step S3, the fluid elastic impedance inversion is performed gradually from a first angle to a third angle in order from the first scale to the third scale, by:
s31, performing fluid elastic impedance inversion of the stacked seismic data of the first to third angles of the first scale
S311, based on the stacked seismic data of the first to third angles of the first scale, focusing a target interval to extract first to third angle wavelets of the first scale;
s312, taking the fluid elastic impedance low-frequency models of the first to third angles calculated in the step S2 as constraints, and performing fluid elastic impedance inversion based on the first to third angle wavelet data of the first scale to obtain fluid elastic impedance data volumes of the first to third angles of the first scale;
s32, performing fluid elastic impedance inversion of the stacked seismic data of the first to third angles of the second scale
S321, based on the first to third angle superposition seismic data of the second scale, focusing a target interval to extract first to third angle wavelets of the second scale;
s322, acquiring the fluid elastic impedance data volumes of the first scale and the third angle in the step S312, and performing low-pass filtering to use the data volumes as low-frequency models required by inversion of the fluid elastic impedance of the first scale and the third angle in the second scale;
s323, taking the low-frequency model in the step S322 as a constraint, and performing fluid elastic impedance inversion based on the wavelet data of the first to third angles of the second scale to obtain a fluid elastic impedance data volume of the first to third angles of the second scale;
s33, performing fluid elastic impedance inversion of the stacked seismic data of the first to third angles of the third scale
S331, based on the first to third angle superposition seismic data of the third scale, focusing a target interval and extracting first to third angle wavelets of the third scale;
s332, acquiring the fluid elastic impedance data volumes of the first angle to the third angle of the second scale in the step 323, and performing low-pass filtering to use the data volumes as low-frequency models required by inversion of the fluid elastic impedance of the first angle to the third angle of the third scale;
s333, taking the low-frequency model in the step S332 as a constraint, and performing fluid elastic impedance inversion based on the wavelet data of the first to third angles in the third scale to obtain fluid elastic impedance data volumes of the first to third angles in the third scale, wherein the fluid elastic impedance data volumes are used as final fluid elastic impedance inversion results of the first to third angles.
8. The method of calculating the Gassmann fluid term according to claim 2, wherein in step S13, the spectral analysis of the target interval at the well side is performed as follows:
i) acquiring the time-depth relation between the post-stack seismic data and the well drilling;
ii) based on the post-stack seismic data, focusing the target interval to extract statistical seismic wavelets and calculating a synthetic seismic record;
iii) carrying out time depth calibration, and defining seismic response characteristics and time range of the target interval;
iv) performing seismic spectrum analysis on the target interval based on the post-stack seismic data.
9. The method of calculating Gassmann fluid terms of claim 5, wherein in step S22, the horizon framework for the interval of interest is established as follows:
I) acquiring the time-depth relation between the post-stack seismic data and the well drilling;
II) focusing the target interval to extract statistical seismic wavelets based on the post-stack seismic data, and calculating a synthetic seismic record;
III) carrying out time-depth calibration, and determining seismic response characteristics and time ranges of the target interval;
IV) focusing the target layer section to start seismic structure interpretation based on the time-depth calibration result of the step III) to obtain a layer position representing the top surface and the bottom surface of the target layer;
v) constructing a horizon frame by utilizing the top surface and the bottom surface of the destination layer explained in the step IV).
10. A system for calculating Gassmann fluid items, comprising:
a data input module configured to acquire first to third angle stack seismic data volumes at first to third scales;
a low-frequency model building module configured to build a fluid elastic impedance low-frequency model of the first to third angles participating in the inversion;
the scale-by-scale inversion module is configured to gradually perform fluid elastic impedance inversion from a first angle to a third angle according to the sequence from the first scale to the third scale, and constrain an optimization process of second scale inversion by taking a first scale inversion result as a prior model, constrain an optimization process of third scale inversion by taking a second scale inversion result as the prior model, and finally obtain fluid elastic impedance inversion results from the first angle to the third angle;
and the data output module is configured to perform logarithmic transformation on the obtained fluid elastic impedance data of the first angle to the third angle, construct a solving equation of the Gassmann fluid item by combining logging statistical information, and obtain final parameters of the Gassmann fluid item.
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