CN110133718B - Attenuation anisotropic fluid elastic impedance inversion method - Google Patents
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Abstract
The invention discloses an attenuation anisotropy fluid elastic impedance inversion method, which comprises the following steps: the method comprises the following steps: acquiring a linear sliding HTI model considering the intrinsic attenuation and fracture induced attenuation of background rocks; step two: establishing a relation equation between the dry elastic modulus and the saturated fluid elastic modulus of the fractured rock; step three: obtaining a real part of complex stiffness of the saturated fluid medium containing the pores and cracks by using the formulas in the first step and the second step; step four: acquiring a PP wave reflection coefficient equation of the dynamic equivalent HTI attenuation medium; step five: acquiring a longitudinal wave reflection coefficient equation; step six: obtaining an azimuth attenuation elastic impedance equation according to the longitudinal wave reflection coefficient equation in the step five; step seven: and inverting the fracture weakness parameter and the fracture induced attenuation parameter by the attenuation elastic impedance difference values in different directions. The inversion method realizes the pre-stack seismic inversion of the background fluid parameters, the fracture characteristic parameters and the attenuation parameters of the fractured reservoir.
Description
Technical Field
The invention relates to the technical field of geophysical exploration of oil and gas resources, in particular to an attenuation anisotropic fluid elastic impedance inversion method.
Background
With the increasing demand for oil and gas in the global scope, the oil and gas exploration direction of geophysicists is gradually changed from the conventional oil and gas reservoir to some special oil and gas reservoirs, wherein the exploration and development of the fractured oil and gas reservoir become the focus of the oil and gas exploration research. Due to the comprehensive influence of factors such as formation pressure and the like, most fractures in the actual formation are high-angle or nearly vertical fractures, and when the fractures develop to a certain scale, transverse wave splitting, azimuth velocity anisotropy characteristics and the like can occur in the propagation of seismic waves in a fractured reservoir and the seismic response of the seismic waves. A single set of vertical cracks developing in the dominant horizontal direction in a homogeneous isotropic background medium can be considered a long wavelength equivalent HTI medium. Therefore, the seismic data are used for describing the seismic response characteristics of the underground medium fractures, and the method has important guiding significance and practical value for exploration and development of fractured reservoirs.
The seismic waves have strong velocity dispersion and attenuation when propagating in an actual fractured reservoir, and the elastic response of the seismic waves has frequency dependence. Previous studies have either only considered intrinsic attenuation of the background medium or only considered the effects of matrix porosity and fluid flow effects; the method establishes an anisotropic fluid elastic impedance inversion method by simultaneously considering the influences of the matrix pore and fluid flow effect, the background intrinsic attenuation and the fracture induced attenuation on the anisotropic pore elasticity approximation theory.
Disclosure of Invention
The present invention is directed to overcoming the above-mentioned deficiencies of the prior art and providing a method for inverting the elastic impedance of a damped anisotropic fluid.
In order to achieve the purpose, the invention adopts the following technical scheme: a method of inverting the elastic impedance of a damped anisotropic fluid, comprising the steps of:
the method comprises the following steps: acquiring a linear sliding HTI model considering the intrinsic attenuation and fracture induced attenuation of background rocks;
step two: establishing a relation equation between the dry elastic modulus and the saturated fluid elastic modulus of the fractured rock;
step three: obtaining a real part of complex stiffness of the saturated fluid medium containing the pores and cracks by using the formulas in the first step and the second step;
step four: acquiring a PP wave reflection coefficient equation of the dynamic equivalent HTI attenuation medium;
step five: acquiring a longitudinal wave reflection coefficient equation;
step six: obtaining an azimuth attenuation elastic impedance equation according to the longitudinal wave reflection coefficient equation in the step five;
step seven: and inverting the fracture weakness parameter and the fracture induced attenuation parameter by the attenuation elastic impedance difference values in different directions.
Preferably, in the first step, the isotropic background modulus parameter and the fracture parameter in the linear sliding HTI model are both expressed in a complex form, and the formula is as follows:
in the formula (1), the first and second groups, andrespectively representing complex longitudinal wave modulus, first and second Lame constants of isotropically attenuating background rock, and
andrepresenting complex normal and tangential fracture attenuation parameters that induce longitudinal and transverse wave attenuation with fractures along the axis of symmetryAndis simply expressed as
Model parameters in complex form under the assumption of isotropic viscoelastic background rockAndcan be expressed as
In the formula (3), the first and second groups,andrespectively representing the inverse quality factors of the longitudinal wave and the transverse wave of the background;
and (3) simultaneously substituting the notations (2) and (3) into the formula (1) to obtain a linear sliding HTI model considering the intrinsic attenuation and the fracture-induced attenuation of the background rock.
Preferably, in the second step, the equation of the relationship between the dry elastic modulus and the saturated fluid elastic modulus of the fractured rock is as follows:
in the formula (4), the first and second groups,is a complex representation of the effective rigidity elastic matrix of the saturated fluid fractured rock,the method is characterized in that the method is a complex representation of an effective rigidity elastic matrix of the dry fractured rock;is a complex characterized anisotropy-like Biot coefficient, which can be expressed as
Wherein, KgRepresenting the effective bulk modulus of the constituent rock solids;is a complex representation of the anisotropic Gassmann pore space modulus, which can be expressed as
In the formula (I), the compound is shown in the specification,is a complex characterized anisotropic dry rock-like bulk modulus; phi represents porosity; kappafRepresenting the pore fluid effective bulk modulus.
Preferably, in the third step, the method for obtaining the real part of the complex stiffness of the pore-containing crack medium of the saturated fluid comprises the following steps:
wherein, the real part of the complex-characterized weak anisotropic stiffness matrix of the dry fracture rock can be expressed as
andrespectively representing comprehensive attenuation factors of the product of background intrinsic longitudinal wave attenuation and transverse wave attenuation and fracture-induced longitudinal wave attenuation;
substituting the formulas (5), (6) and (7) into the formula (4), and obtaining an approximate expression of the real part of the complex stiffness of the saturated fluid medium containing the pore gaps, which is characterized by the modulus of the background dry rock, the flexibility of the dry gaps, the modulus of the fluid, the intrinsic longitudinal and transverse wave attenuation of the background and the induced longitudinal wave attenuation of the gaps, in the seismic frequency range on the basis of the weak anisotropy approximation and the weak intrinsic attenuation approximation of the background
β0=1-Kdry/Kgis the Biot coefficient;
Kdryrepresenting the bulk modulus of the dry rock.
Preferably, in the fourth step, the method for obtaining the PP wave reflection coefficient equation is as follows:
based on scattering theory, the longitudinal wave reflection coefficient of HTI media can be expressed as:
where θ represents the angle of incidence, ρ represents the density term of the homogeneous isotropic background medium,parameter, ξ, representing the disturbance stiffness of saturated rockmnRelated to slowness vectors and polarization vectors;
therefore, by combining the equations (8) and (9), the equation of the reflection coefficient of the PP wave of the dynamic equivalent HTI attenuation medium can be derived, and the expression is
in the formula (10), the first and second groups,representing the azimuth angle, delta representing the difference of each property of the two layers of media, and f is fluid/pore and is a fluid factor; the fracture weakness parameter can be estimated according to logging data and a rock physical model;
preferably, in the fifth step, according to the relationship between the longitudinal wave reflection coefficient of the horizontal interface and the elastic impedance of the azimuthal anisotropy, the longitudinal wave reflection coefficient equation can be expressed as:
in the formula (11), the reaction mixture,represents the azimuthal attenuation elastic resistance, and Δ EI (θ, Φ) represents the difference between the elastic resistances of the previous and next layers.
Preferably, in the sixth step, the method for obtaining the azimuth attenuation elastic impedance equation from the longitudinal wave reflection coefficient equation of the fifth step is as follows:
in the weak elastic parameter difference (| delta f/f | < 1, | delta mu/mub1 and [ Delta ] rho/rhob< 1), small crack weakness (And isT< 1) and weak attenuation (And is) Under the assumption of the conditions that,
the relative difference in background elastic modulus in equation (11) can be approximately replaced by:
Δf/f≈Δ(lnf),
Δμ/μb≈Δ(lnμb),
under the assumption of continuous change of elastic parameters, crack parameters, attenuation parameters and elastic impedance parameters, delta (ln f) is approximately equal to d (ln f), and delta (ln mu)b)≈d(lnμb),Δ(lnρb)≈d(lnρb),ΔT≈dT,And is
Substituting the above approximate substitution into equation (11) yields the following equation:
the integral of the formula (12) is calculated, and the logarithmic domain azimuth attenuation elastic impedance equation is obtained through corresponding operation, and is expressed as
Taking the logarithm of equation (13), the final azimuthal attenuation elastic impedance equation can be expressed as
Preferably, in the seventh step, the inversion of the fracture weakness parameter and the fracture-induced attenuation parameter according to the attenuation elastic impedance difference values in different directions includes the following steps:
step 7-1: carrying out difference linearization processing on the attenuation elastic impedance in different directions of the logarithmic domain to obtain a difference linearization expression as shown in the following formula;
in formula (15), M is the number of incident angles, N is the number of azimuthal angle differences, and L is the number of reflective interfaces;is the difference in elastic impedance, m, in different directions in the logarithmic domaincQIs the fracture weakness and fracture induced attenuation parameters to be inverted, and Δ X is a positive operator matrix associated with the different azimuth reflection coefficient weight difference operator matrix Δ A, which can be expressed as
Step 7-2: performing decorrelation and normalization processing on the difference value linearization expression to obtain a positive problem after decorrelation;
decorrelation and normalization processing among model parameters are considered in inversion of logarithm domain azimuth elastic impedance difference, and a kernel matrix delta X after the decorrelation becomesDynamic domain model parameter vector mcQBecome intoThe decorrelated positive problem can be expressed as
And 7-3: converting the decorrelated positive problem into a target function;
using the Cauchy probability distribution as the prior probability density function and the Gaussian distribution as the likelihood function, the posterior probability density function is solved using a joint probability density function of the prior probability density function and the likelihood function, i.e.
In the formula (17), the reaction is carried out,is the variance of the noise, and is,is the variance of the quasi-static domain model parameter vector. Taking a maximum posterior probability density function of the formula (17), combining with the low-frequency information regularization constraint term of the initial model, and finally representing the target function as
In the formula (18), the first and second groups,is a regularization coefficient of the quasi-static domain model parameters;
And 7-4: solving an objective function;
the objective function equation (18) is solved to obtain
QCauchyrepresents the Cauchy sparse matrix and the matrix,
and 7-5: and (3) carrying out iterative solution on the formula (19) by adopting an iterative reweighted least square optimization algorithm to obtain a dynamic domain model parameter vector, wherein the formula is as follows:
the invention has the following beneficial effects:
according to the method, the intrinsic attenuation and the induced attenuation of the fracture rock background are comprehensively considered, a relational equation between the dry elastic modulus and the saturated fluid elastic modulus of the fracture rock represented by a plurality of factors is combined, and an approximate expression of the complex stiffness real part of the saturated fluid medium containing the pores and characterized by the background dry rock modulus, the dry fracture flexibility, the fluid modulus, the background intrinsic longitudinal and transverse wave attenuation and the fracture induced longitudinal wave attenuation is obtained in the seismic frequency range on the basis of the weak anisotropy approximation and the weak background intrinsic attenuation approximation; based on a scattering theory, a PP wave reflection coefficient equation of a dynamic equivalent HTI attenuation medium is deduced, and an azimuth attenuation elastic impedance equation is deduced according to a longitudinal wave reflection coefficient equation under the assumption conditions of weak elastic parameter difference, small crack weakness and weak attenuation and under the assumption conditions of continuous change of elastic parameters, crack parameters, attenuation parameters and elastic impedance parameters; a sparse constraint regularization and low-frequency information constraint regularization azimuth attenuation elastic impedance iterative inversion method is provided, and prestack seismic inversion of background fluid parameters, fracture characteristic parameters and attenuation parameters of a fractured reservoir is realized.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a flow chart of a method for inverting the elastic impedance of a damped anisotropic fluid according to the present invention;
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The invention is further illustrated with reference to the following figures and examples.
A method of inverting the elastic impedance of a damped anisotropic fluid, as shown in fig. 1, comprising the steps of:
the method comprises the following steps: acquiring a linear sliding HTI model considering the intrinsic attenuation and fracture induced attenuation of background rocks;
preferably, in the first step, the isotropic background modulus parameter and the fracture parameter in the linear sliding HTI model are both expressed in a complex form, and the formula is as follows:
in the formula (1), the first and second groups, andrespectively representing complex longitudinal wave modulus, first and second Lame constants of isotropically attenuating background rock, and
andrepresenting complex normal and tangential fracture attenuation parameters that induce longitudinal and transverse wave attenuation with fractures along the axis of symmetryAndis simply expressed as
Bringing the expression (2) into the formula (1) to obtain a linear sliding HTI model considering fracture-induced fracture induced attenuation;
model parameters in complex form under the assumption of isotropic viscoelastic background rockAndcan be expressed as
In the formula (3), the first and second groups,andrespectively representing the inverse quality factors of the longitudinal wave and the transverse wave of the background;
substituting the public representation (3) into the formula (1) to obtain a linear sliding HTI model considering the intrinsic attenuation of the background rock;
and (3) simultaneously substituting the notations (2) and (3) into the formula (1) to obtain a linear sliding HTI model considering the intrinsic attenuation and the fracture-induced attenuation of the background rock.
Step two: establishing a relation equation between the dry elastic modulus and the saturated fluid elastic modulus of the fractured rock;
preferably, in the second step, the equation of the relationship between the dry elastic modulus and the saturated fluid elastic modulus of the fractured rock is as follows:
in the formula (4), the first and second groups,is a complex representation of the effective rigidity elastic matrix of the saturated fluid fractured rock,the method is characterized in that the method is a complex representation of an effective rigidity elastic matrix of the dry fractured rock;is a complex characterized anisotropy-like Biot coefficient, which can be expressed as
Wherein, KgRepresenting the effective bulk modulus of the constituent rock solids;is a complex representation of the anisotropic Gassmann pore space modulus, which can be expressed as
In the formula (I), the compound is shown in the specification,is a complex characterized anisotropic dry rock-like bulk modulus; phi represents porosity; kappafRepresenting the pore fluid effective bulk modulus.
Step three: obtaining a real part of complex stiffness of the saturated fluid medium containing the pores and cracks by using the formulas in the first step and the second step;
preferably, in the third step, the method for obtaining the real part of the complex stiffness of the pore-containing crack medium of the saturated fluid comprises the following steps:
the prior research shows that the imaginary part of the reflection coefficient represented by a complex number is far smaller than the real part, so that only the derivation of the real part of the reflection coefficient is focused on in the invention, and the imaginary part of the reflection coefficient is ignored;
wherein, the real part of the complex-characterized weak anisotropic stiffness matrix of the dry fracture rock can be expressed as
andrespectively representing comprehensive attenuation factors of the product of background intrinsic longitudinal wave attenuation and transverse wave attenuation and fracture-induced longitudinal wave attenuation;
where the parameters in the formula of the invention with superscript dry all represent parameters in the case of dry rock (no fluid in the pores), for example:complex longitudinal wave modulus of isotropically damped background rock is shown, thenThen the complex longitudinal wave modulus of the isotropically attenuated dry background rock is represented;
substituting the formulas (5), (6) and (7) into the formula (4), and obtaining an approximate expression of the real part of the complex stiffness of the saturated fluid medium containing the pore gaps, which is characterized by the modulus of the background dry rock, the flexibility of the dry gaps, the modulus of the fluid, the intrinsic longitudinal and transverse wave attenuation of the background and the induced longitudinal wave attenuation of the gaps, in the seismic frequency range on the basis of the weak anisotropy approximation and the weak intrinsic attenuation approximation of the background
β0=1-Kdry/Kgis the Biot coefficient;
Kdryrepresenting the bulk modulus of the dry rock.
Step four: acquiring a PP wave reflection coefficient equation of the dynamic equivalent HTI attenuation medium;
preferably, in the fourth step, the method for obtaining the PP wave reflection coefficient equation is as follows:
based on scattering theory, the longitudinal wave reflection coefficient of HTI media can be expressed as:
where θ represents the angle of incidence, ρ represents the density term of the homogeneous isotropic background medium,parameter, ξ, representing the disturbance stiffness of saturated rockmnRelated to slowness vectors and polarization vectors;
thus, in combination with equations (8) and (9), a dynamic equivalent HTI attenuation can be derivedEquation of PP wave reflection coefficient of medium, specifically, for equation (9)Is subjected to derivation and then is subjected to ximnThe formula (10) can be obtained by multiplying and neglecting small terms, and the expression is
in the formula (10), the first and second groups,representing the azimuth angle, delta representing the difference of each property of the two layers of media, and f is fluid/pore and is a fluid factor; the fracture weakness parameter can be estimated according to logging data and a rock physical model;
wherein the parameters with superscript sat in the present invention all represent parameters in the case of saturated fluids.
Step five: acquiring a longitudinal wave reflection coefficient equation;
preferably, in the fifth step, according to the relationship between the longitudinal wave reflection coefficient of the horizontal interface and the elastic impedance of the azimuthal anisotropy, the longitudinal wave reflection coefficient equation can be expressed as:
in the formula (11), the reaction mixture,represents the azimuth attenuation elastic impedance, and delta EI (theta, phi) represents the difference between the elastic impedance of the upper layer and the elastic impedance of the lower layer;
where the longitudinal wave is a p-wave and pp means that both incident and reflected are p-waves.
Step six: obtaining an azimuth attenuation elastic impedance equation according to the longitudinal wave reflection coefficient equation in the step five;
preferably, in the sixth step, the method for obtaining the azimuth attenuation elastic impedance equation from the longitudinal wave reflection coefficient equation of the fifth step is as follows:
in the weak elastic parameter difference (| delta f/f | < 1, | delta mu/mub1 and [ Delta ] rho/rhob< 1), small crack weakness (And isT< 1) and weak attenuation (And is) Under the assumption of the conditions that,
the relative difference in background elastic modulus in equation (11) can be approximately replaced by:
Δf/f≈Δ(lnf),
Δμ/μb≈Δ(lnμb),
under the assumption of continuous change of elastic parameters, crack parameters, attenuation parameters and elastic impedance parameters, delta (ln f) is approximately equal to d (ln f), and delta (ln mu)b)≈d(lnμb),Δ(lnρb)≈d(lnρb),ΔT≈dT,And is
Substituting the above approximate substitution into equation (11) yields the following equation:
the integral of the formula (12) is calculated, and the logarithmic domain azimuth attenuation elastic impedance equation is obtained through corresponding operation, and is expressed as
Taking the logarithm of equation (13), the final azimuthal attenuation elastic impedance equation can be expressed as
Step seven: and inverting the fracture weakness parameter and the fracture induced attenuation parameter by the attenuation elastic impedance difference values in different directions.
Preferably, in the seventh step, the inversion of the fracture weakness parameter and the fracture-induced attenuation parameter according to the attenuation elastic impedance difference values in different directions includes the following steps:
step 7-1: carrying out difference linearization processing on the attenuation elastic impedance in different directions of the logarithmic domain to obtain a difference linearization expression as shown in the following formula;
in formula (15), M is the number of incident angles, N is the number of azimuthal angle differences, and L is the number of reflective interfaces;is the difference in elastic impedance, m, in different directions in the logarithmic domaincQIs the fracture weakness and fracture induced attenuation parameters to be inverted, and Δ X is a positive operator matrix associated with the different azimuth reflection coefficient weight difference operator matrix Δ A, which can be expressed as
Step 7-2: performing decorrelation and normalization processing on the difference value linearization expression to obtain a positive problem after decorrelation;
decorrelation and normalization processing among model parameters are considered in inversion of logarithm domain azimuth elastic impedance difference, and a kernel matrix delta X after the decorrelation becomesDynamic domain model parameter vector mcQBecome intoThe decorrelated positive problem can be expressed as
And 7-3: converting the decorrelated positive problem into a target function;
using the Cauchy probability distribution as the prior probability density function and the Gaussian distribution as the likelihood function, the posterior probability density function is solved using a joint probability density function of the prior probability density function and the likelihood function, i.e.
Here the bayesian principle is applied: the posterior distribution is equal to prior probability multiplied by likelihood function, and the positive problem after decorrelation is processed;
in the formula (17), the reaction is carried out,is the variance of the noise, and is,is the variance of the quasi-static domain model parameter vector. The maximum a posteriori probability density function is taken for equation (17),combining with the low-frequency information regularization constraint term of the initial model, and performing logarithm transformation to finally express the objective function as
In the formula (18), the first and second groups,is a regularization coefficient of the quasi-static domain model parameters;
And 7-4: solving an objective function;
the objective function equation (18) is solved to obtain
QCauchyrepresents the Cauchy sparse matrix and the matrix,
and 7-5: and (3) carrying out iterative solution on the formula (19) by adopting an iterative reweighted least square optimization algorithm to obtain a dynamic domain model parameter vector, wherein the formula is as follows:
the reliability of the azimuth attenuation elastic impedance inversion method provided by the invention is verified by using the synthesized azimuth prestack seismic gather: when the synthetic gather does not contain noise or contains proper noise, the inversion result of the model parameters inverted by the inversion method is well matched with actual data. Compared with the original gather, the difference between the azimuth angle gather synthesized by the model parameter inversion result and the original gather is small, and the feasibility of the azimuth attenuation elastic impedance inversion method is further verified.
According to the method, the intrinsic attenuation and the induced attenuation of the fracture rock background are comprehensively considered, a relational equation between the dry elastic modulus and the saturated fluid elastic modulus of the fracture rock represented by a plurality of factors is combined, and an approximate expression of the complex stiffness real part of the saturated fluid medium containing the pores and characterized by the background dry rock modulus, the dry fracture flexibility, the fluid modulus, the background intrinsic longitudinal and transverse wave attenuation and the fracture induced longitudinal wave attenuation is obtained in the seismic frequency range on the basis of the weak anisotropy approximation and the weak background intrinsic attenuation approximation; based on a scattering theory, a PP wave reflection coefficient equation of a dynamic equivalent HTI attenuation medium is deduced, and an azimuth attenuation elastic impedance equation is deduced according to a longitudinal wave reflection coefficient equation under the assumption conditions of weak elastic parameter difference, small crack weakness and weak attenuation and under the assumption conditions of continuous change of elastic parameters, crack parameters, attenuation parameters and elastic impedance parameters; a sparse constraint regularization and low-frequency information constraint regularization azimuth attenuation elastic impedance iterative inversion method is provided, and prestack seismic inversion of background fluid parameters, fracture characteristic parameters and attenuation parameters of a fractured reservoir is realized.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the present invention, and it should be understood by those skilled in the art that various modifications and changes may be made without inventive efforts based on the technical solutions of the present invention.
Claims (7)
1. An inversion method of damping anisotropic fluid elastic impedance is characterized by comprising the following steps:
the method comprises the following steps: acquiring a linear sliding HTI model considering the intrinsic attenuation and fracture induced attenuation of background rocks;
step two: establishing a relation equation between the dry elastic modulus and the saturated fluid elastic modulus of the fractured rock;
step three: obtaining a real part of complex stiffness of the saturated fluid medium containing the pores and cracks by using the formulas in the first step and the second step;
step four: acquiring a PP wave reflection coefficient equation of the dynamic equivalent HTI attenuation medium;
step five: acquiring a longitudinal wave reflection coefficient equation;
step six: obtaining an azimuth attenuation elastic impedance equation according to the longitudinal wave reflection coefficient equation in the step five;
step seven: inverting the fracture weakness parameter and the fracture induced attenuation parameter by the attenuation elastic impedance difference values in different directions;
in the seventh step, the inversion of the fracture weakness parameter and the fracture induced attenuation parameter is carried out by the attenuation elastic impedance difference values in different directions, and the inversion comprises the following steps:
step 7-1: carrying out difference linearization processing on the attenuation elastic impedance in different directions of the logarithmic domain to obtain a difference linearization expression as shown in the following formula;
in formula (15), M is the number of incident angles, N is the number of azimuthal angle differences, and L is the number of reflective interfaces;is the difference in elastic impedance, m, in different directions in the logarithmic domaincQIs the fracture weakness and fracture induced attenuation parameters to be inverted, and Δ X is a positive operator matrix associated with the different azimuth reflection coefficient weight difference operator matrix Δ A, which can be expressed as
Step 7-2: performing decorrelation and normalization processing on the difference value linearization expression to obtain a positive problem after decorrelation;
decorrelation and normalization processing among model parameters are considered in inversion of logarithm domain azimuth elastic impedance difference, and a kernel matrix delta X after the decorrelation becomesDynamic domain model parameter vector mcQBecome intoThe decorrelated positive problem can be expressed as
And 7-3: converting the decorrelated positive problem into a target function;
using the Cauchy probability distribution as the prior probability density function and the Gaussian distribution as the likelihood function, the posterior probability density function is solved using a joint probability density function of the prior probability density function and the likelihood function, i.e.
In the formula (17), the reaction is carried out,is the variance of the noise, and is,is the variance of the quasi-static domain model parameter vector; taking a maximum posterior probability density function of the formula (17), combining with the low-frequency information regularization constraint term of the initial model, and finally representing the target function as
In the formula (18), the first and second groups,is a regularization coefficient of the quasi-static domain model parameters;
and 7-4: solving an objective function;
the objective function equation (18) is solved to obtain
QCauchyrepresents the Cauchy sparse matrix and the matrix,
and 7-5: and (3) carrying out iterative solution on the formula (19) by adopting an iterative reweighted least square optimization algorithm to obtain a dynamic domain model parameter vector, wherein the formula is as follows:
2. the method of claim 1, wherein in the first step, the isotropic background modulus parameter and the fracture parameter in the linear sliding HTI model are both expressed in complex form, and the formula is as follows:
in the formula (1), the first and second groups, andrespectively representing complex longitudinal wave modulus, first and second Lame constants of isotropically attenuating background rock, and
andrepresenting complex normal and tangential fracture attenuation parameters that induce longitudinal and transverse wave attenuation with fractures along the axis of symmetryAndis simply expressed as
Model parameters in complex form under the assumption of isotropic viscoelastic background rockAndcan be expressed as
In the formula (3), the first and second groups,andrespectively representing the inverse quality factors of the longitudinal wave and the transverse wave of the background;
and (3) simultaneously substituting the notations (2) and (3) into the formula (1) to obtain a linear sliding HTI model considering the intrinsic attenuation and the fracture-induced attenuation of the background rock.
3. The method for inverting the elastic impedance of the damping anisotropic fluid according to claim 2, wherein in the second step, the equation of the relationship between the dry elastic modulus and the saturated elastic modulus of the fractured rock is as follows:
in the formula (4), the first and second groups,is a complex representation of the effective rigidity elastic matrix of the saturated fluid fractured rock,the method is characterized in that the method is a complex representation of an effective rigidity elastic matrix of the dry fractured rock;is a complex characterized anisotropy-like Biot coefficient, which can be expressed as
Wherein, KgRepresenting the effective bulk modulus of the constituent rock solids;is a complex representation of the anisotropic Gassmann pore space modulus, which can be expressed as
4. The method for inverting the elastic impedance of the damped anisotropic fluid as set forth in claim 3, wherein in the third step, the method for obtaining the real part of the complex stiffness of the interstitial fracture medium of the saturated fluid comprises the following steps:
wherein, the real part of the complex-characterized weak anisotropic stiffness matrix of the dry fracture rock can be expressed as
andrespectively representing comprehensive attenuation factors of the product of background intrinsic longitudinal wave attenuation and transverse wave attenuation and fracture-induced longitudinal wave attenuation;
substituting the formulas (5), (6) and (7) into the formula (4), and obtaining an approximate expression of the real part of the complex stiffness of the saturated fluid medium containing the pore gaps, which is characterized by the modulus of the background dry rock, the flexibility of the dry gaps, the modulus of the fluid, the intrinsic longitudinal and transverse wave attenuation of the background and the induced longitudinal wave attenuation of the gaps, in the seismic frequency range on the basis of the weak anisotropy approximation and the weak intrinsic attenuation approximation of the background
β0=1-Kdry/Kgis the Biot coefficient;
Kdryrepresenting the bulk modulus of the dry rock.
5. The method for inverting the damped anisotropic fluid elastic impedance as claimed in claim 4, wherein in the fourth step, the method for obtaining the PP wave reflection coefficient equation is as follows:
based on scattering theory, the longitudinal wave reflection coefficient of HTI media can be expressed as:
where θ represents the angle of incidence, ρ represents the density term of the homogeneous isotropic background medium,parameter, ξ, representing the disturbance stiffness of saturated rockmnRelated to slowness vectors and polarization vectors;
therefore, by combining the equations (8) and (9), the equation of the reflection coefficient of the PP wave of the dynamic equivalent HTI attenuation medium can be derived, and the expression is
6. The method of inverting an attenuating anisotropic fluid elastic impedance of claim 5, wherein in step five, based on the relationship between the horizontal interface longitudinal wave reflection coefficient and the azimuthal anisotropic elastic impedance, the longitudinal wave reflection coefficient equation is expressed as:
7. The method for inverting the damped anisotropic fluid elastic impedance as claimed in claim 6, wherein in step six, the method for obtaining the azimuthal damped elastic impedance equation from the longitudinal wave reflection coefficient equation of step five is as follows:
in the weak elastic parameter difference (| delta f/f | < 1, | delta mu/mub1 and [ Delta ] rho/rhobLess than 1) small crack weaknessAnd weak attenuationUnder the assumption of the conditions that,
the relative difference in background elastic modulus in equation (11) can be approximately replaced by:
Δf/f≈Δ(lnf),
Δμ/μb≈Δ(lnμb),
under the assumption of continuous change of elastic parameters, crack parameters, attenuation parameters and elastic impedance parameters, delta (ln f) is approximately equal to d (ln f), and delta (ln mu)b)≈d(lnμb),Δ(lnρb)≈d(lnρb),ΔT≈dT,And is
Substituting the above approximate substitution into equation (11) yields the following equation:
the integral of the formula (12) is calculated, and the logarithmic domain azimuth attenuation elastic impedance equation is obtained through corresponding operation, and is expressed as
Taking the logarithm of equation (13), the final azimuthal attenuation elastic impedance equation can be expressed as
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