Petrophysical modeling method for rock structure and fluid distribution dual heterogeneity

Abstract

This invention relates to a rock physics modeling method for dual heterogeneity of rock structure and fluid distribution. On one hand, the rock skeleton is equivalent to two parts: a highly consolidated background phase and a poorly consolidated heterogeneous phase, thus characterizing the heterogeneity of the rock structure. On the other hand, the fluid is assumed to be partially saturated within the rock skeleton, thus describing the heterogeneity of the fluid distribution. The equivalent elastic modulus of the two different fluid-saturated phases is calculated using a dual-porosity model, and these are used as input moduli in a porphyritic saturation model, thereby establishing a dual heterogeneity model. This model directly and effectively characterizes the combined effect of dual heterogeneity and the resulting dispersion response of elastic parameters. Theoretical model calculations are performed to analyze the influence of the two heterogeneities on the dispersion characteristics of elastic parameters. Furthermore, the dual heterogeneity model is calibrated using laboratory measurements from rock core samples, determining the parameters within the model. This model can more accurately interpret the laboratory measurement results.

Description

Technical Field

[0001] This invention belongs to the field of rock physics technology, specifically relating to a rock physics modeling method for the dual heterogeneity of rock structure and fluid distribution. Background Technology

[0002] Existing theoretical studies indicate that the elastic properties of rocks are frequency-dependent. The dispersion response of elastic properties within the seismic frequency band is crucial for reservoir fluid identification, and its physical mechanism is typically explained as wave-induced fluid flow caused by mesoscopic heterogeneity. This mesoscopic heterogeneity includes the heterogeneity of rock structure and fluid distribution. Currently, modeling is generally based on classical rock physics models that consider both heterogeneities separately, or on wave theory-based models that simultaneously consider both heterogeneities. Ba et al. simulated the influence of rock structure and fluid distribution on seismic wave propagation characteristics based on wave theory and calibrated the model using experimental data, verifying the importance of considering dual heterogeneity in seismic wave dispersion mechanism research. However, both wave theory-based modeling methods and the characterization of mesoscopic heterogeneity parameters are quite complex.

[0003] Therefore, it is necessary to establish a rock physics model that can directly and effectively describe the comprehensive effects of mesoscopic heterogeneity. This model can accurately simulate the dispersion response of elastic parameters within the seismic band caused by the dual heterogeneity of rock structure and fluid distribution, so as to more comprehensively and reasonably explain the rock physics mechanism of mesoscopic-scale dispersion. Summary of the Invention

[0004] The purpose of this invention is to provide a rock physics modeling method for the dual heterogeneity of rock structure and fluid distribution, so as to solve the problem of accurately characterizing the combined influence of the dual heterogeneity of rock structure and fluid distribution on the dispersion response of elastic parameters within the seismic band in a direct and effective manner.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A rock physics modeling method for rock structures and fluid distribution exhibiting dual heterogeneity includes the following steps:

[0007] A. Based on the mineral composition of the rock, calculate the bulk modulus, shear modulus, and density of the solid matrix of the rock using the Hashin-Shtrikman limit theory.

[0008] B. The porous rock skeleton is equivalent to two parts: a background phase with a high degree of consolidation and a heterogeneous phase with a low degree of consolidation. This is used to characterize the heterogeneity of the rock structure. The volume fraction, porosity, permeability and consolidation parameters of the two phases of the rock skeleton are determined according to the rock properties.

[0009] C. Based on the elastic modulus of the solid matrix calculated in step A, and the porosity and consolidation parameters of the two phases of the rock skeleton given in step B, calculate the bulk modulus and shear modulus of the two phases of the rock skeleton respectively based on the effective medium theory.

[0010] D. Assume that the fluid is partially saturated in the rock skeleton to describe the heterogeneity of the fluid distribution. Give the bulk modulus, shear modulus, density and viscosity coefficient of the two fluids respectively.

[0011] E. Using the elastic properties of the solid matrix obtained in step A, the properties of the two phases of the rock skeleton obtained in steps B and C, and the properties of the two-phase fluid given in step D, calculate the equivalent elastic modulus of the two different fluid saturated phases based on the dual-pore model.

[0012] F. Calculate the harmonic mean of the rock skeleton properties of the background phase and heterogeneous phase obtained in step B to obtain the properties of the composite phase;

[0013] G. The elastic properties of the solid matrix obtained in step A, the properties of the two-phase fluid given in step D, and the properties of the composite phase calculated in step F are used as inputs to the two-phase fluid and skeleton parameters in the porphyritic saturation model. The equivalent elastic moduli of the two different fluid saturated phases calculated in step E are used as input moduli in the porphyritic saturation model, thereby establishing a rock physics model that considers the dual heterogeneity of rock structure and fluid distribution.

[0014] H. Use the dual heterogeneity model established in step G to carry out theoretical model calculations and analyze the influence of the degree of heterogeneity of rock structure and fluid distribution on the dispersion characteristics of elastic parameters.

[0015] I. The dual heterogeneity model was calibrated using laboratory measurement results from core samples to verify the advantages and applicability of the model established in this invention.

[0016] Furthermore, in step E, the equivalent elastic modulus of the two different fluid saturated phases is calculated based on the dual-pore model:

[0017]

[0018]

[0019]

[0020] Where, constant a ij (i, j = 1, 2) are constants, K d * It is the effective drainage bulk modulus of a dual-porosity medium, B * It is the effective Skempton coefficient, K u *It is the effective undrained bulk modulus.

[0021] Furthermore, the equivalent elastic modulus of the two different fluid saturated phases calculated by the dual-pore model includes the dispersion response associated with the non-uniform rock structure.

[0022] Furthermore, in step G, the equivalent elastic modulus containing two different fluid saturated phases, calculated using the dual-pore model, is used as the input modulus of the porphyritic saturation model, thus realizing the consideration of the influence of non-uniform fluid distribution in the context of non-uniform rock structure.

[0023] Furthermore, by integrating the dual-pore model describing the heterogeneity of rock structure and the porphyritic saturation model describing the heterogeneity of fluid distribution, a dual heterogeneity model is established. This model directly and accurately characterizes the combined effect of dual heterogeneity and the resulting dispersion response of elastic parameters, providing a more comprehensive and reasonable explanation for the mesoscale dispersion mechanism of rock physics.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention provides a rock physics modeling method for the dual heterogeneity of rock structure and fluid distribution. Based on the dual-porosity model describing the heterogeneity of rock structure and the porphyritic saturation model describing the heterogeneity of fluid distribution, a dual heterogeneous rock physics modeling method is proposed. This method can accurately characterize the combined effect of the dual heterogeneity of rock structure and fluid distribution and the resulting dispersion response of elastic parameters in a direct and effective manner, providing a more comprehensive and reasonable explanation for the mesoscale dispersion rock physics mechanism. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 It is a flowchart for rock physics modeling that addresses the dual heterogeneity of rock structure and fluid distribution.

[0028] Figure 2 This is a schematic diagram of the frequency-varying longitudinal wave velocity calculated by the dual heterogeneity model and the patchy saturation model for different heterogeneous phase ratios.

[0029] Figure 3 This is a schematic diagram of the frequency-varying longitudinal wave velocity calculated by the dual heterogeneity model and the patchy saturation model at different gas saturation levels.

[0030] Figure 4 This is a schematic diagram of the frequency-varying longitudinal wave velocity calculated by the dual heterogeneity model, porphyritic saturation model, and dual-porosity model under specific conditions where the rock skeleton is saturated with only one type of fluid or where there is no heterogeneous phase.

[0031] Figure 5 This is a schematic diagram comparing the bulk modulus dispersion simulated by the dual heterogeneity model, the patchy saturation model, and the dual-porosity model with laboratory measurement results.

[0032] Figure 6 This is a schematic diagram comparing the Young's modulus dispersion simulated by the dual heterogeneity model, the patchy saturation model, and the dual-porosity model with the laboratory measurement results. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments:

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0035] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] This invention addresses a rock physics modeling method for the dual heterogeneity of rock structure and fluid distribution. Based on conventional dual-porosity and porphyritic saturation models, it comprehensively considers the heterogeneity of both rock structure and fluid distribution to establish a dual-heterogeneity rock physics model. This model can directly and effectively characterize the combined effects of dual heterogeneity and the resulting elastic parameter dispersion response, providing a more comprehensive and reasonable explanation for studying the rock physics mechanism of mesoscale elastic parameter dispersion. The specific implementation scheme of this invention to achieve the above objectives is as follows:

[0037] Step 1: Based on the mineral composition of the rock, calculate the bulk modulus, shear modulus, and density of the solid matrix of the rock using the Hashin-Shtrikman limit theory.

[0038] Step 2: The porous rock skeleton is equivalent to two parts: a background phase with a high degree of consolidation and a heterogeneous phase with a low degree of consolidation. This is used to characterize the heterogeneity of the rock structure, and the volume fraction, porosity, permeability, consolidation parameters, etc. of each phase are determined according to the rock properties.

[0039] Step 3: Based on the elastic modulus of the solid matrix calculated in Step 1, and the porosity and consolidation parameters of the two phases given in Step 2, calculate the bulk modulus and shear modulus of the two phases of the rock skeleton respectively based on the effective medium theory.

[0040] Step 4: Assume that the fluid is partially saturated in the rock skeleton to describe the heterogeneity of the fluid distribution. Give the bulk modulus, shear modulus, density and viscosity coefficient of the two fluids respectively.

[0041] Step 5: Using the elastic properties of the solid matrix obtained in Step 1, the properties of the two phases of the rock skeleton obtained in Steps 2 and 3, and the properties of the two-phase fluid given in Step 4, calculate the equivalent elastic modulus of the two different fluid saturated phases based on the dual-pore model.

[0042] Step 6: Calculate the harmonic mean of the rock skeleton properties of the background phase and heterogeneous phase obtained in Step 2 to obtain the properties of the composite phase;

[0043] Step 7: The elastic properties of the solid matrix obtained in Step 1, the properties of the two-phase fluid given in Step 4, and the properties of the composite phase calculated in Step 6 are used as inputs for the two-phase fluid and skeleton parameters in the porphyritic saturation model. The equivalent elastic moduli of the two different fluid saturated phases calculated in Step 5 are used as input moduli in the porphyritic saturation model, thereby establishing a rock physics model that considers the dual heterogeneity of rock structure and fluid distribution.

[0044] Step 8: Use the dual heterogeneity model established in Step 7 to perform theoretical model calculations and analyze the influence of the degree of heterogeneity of rock structure and fluid distribution on the dispersion characteristics of elastic parameters.

[0045] Step 9: Apply laboratory measurement results from core samples to calibrate the dual heterogeneity model and verify the advantages and applicability of the model established in this invention.

[0046] This invention uses the equivalent elastic modulus of two different fluid saturated phases calculated by the dual-pore model as the input modulus of the porphyritic saturation model, and considers the influence of non-uniform fluid distribution in the context of non-uniform rock structure, thereby establishing a dual heterogeneity model to accurately simulate the dispersion response of elastic parameters related to the dual heterogeneity of rock structure and fluid distribution.

[0047] The theoretical calculation results of the established dual heterogeneity model show that the degree of heterogeneity of rock structure and fluid distribution has a significant impact on the dispersion of elastic parameters. Furthermore, under the specific conditions that the rock skeleton is saturated by only one type of fluid or there is no heterogeneous phase, the dispersion of elastic parameters is completely controlled by one type of heterogeneity. In this case, the model can completely degenerate into a conventional dual-porosity model and a porphyritic saturation model, respectively, which theoretically proves the self-consistency of the model established in this invention.

[0048] The dual heterogeneity model was calibrated using laboratory measurements from core samples, and the parameters in the model were determined. The calibration results showed that the model could more accurately interpret the laboratory measurement results compared with the conventional dual-porosity model and the porphyritic saturation model. This demonstrated that the model established in this invention can more comprehensively and reasonably explain the rock physical mechanism of mesoscale elastic parameter dispersion, and verified the advantages and applicability of the model established in this invention.

[0049] The basic principle of the rock physics modeling method for the dual heterogeneity of rock structure and fluid distribution provided by this invention is as follows:

[0050] Knowing the volume fraction and elastic properties of the minerals in a rock, the elastic modulus of the solid matrix can be estimated using the Hashin-Shtrikman limit theory (Hashin and Shtrikman, 1963). For multiple mineral compositions, the formulas for calculating the volume modulus and shear modulus of the solid matrix are (Berryman, 1995):

[0051]

[0052] in,

[0053]

[0054]

[0055]

[0056] Among them, K s and μ s HS+ and HS- represent the bulk modulus and shear modulus of the rock solid matrix, respectively; the superscripts HS+ and HS- represent the upper and lower limits of the elastic modulus, respectively; K and μ represent the bulk modulus and shear modulus of the mineral components, respectively; the subscripts max and min represent the maximum and minimum values ​​of the elastic modulus among the mineral components, respectively; r represents the r-th mineral component; <·> represents the weighted average of the various mineral components in the solid matrix. Finally, the elastic modulus of the rock solid matrix is ​​the average of the upper and lower limits of the elastic modulus in formula (1).

[0057] Pride and Berryman (2003) proposed a dual-porosity model to describe mesoscopic heterogeneity, in which the porous phase consists of a single fluid-saturated background phase and a heterogeneous phase. The governing equations of the dual-porosity model in the frequency domain are:

[0058] ▽·τ D -▽p c =-iω(ρv+ρ f q1+ρf q2), (5)

[0059]

[0060]

[0061] -iωζ int =γ(ω)(p f1 -p f2 (8)

[0062]

[0063] In formula (5), τ D and p c Represent the average values ​​of the deviatoric stress and confining pressure within the average volume of the porous composite material, respectively; v is the average velocity of the solid particles; q1 and q2 are the average velocities of the fluid in the background phase and the heterogeneous phase, respectively; ρ and ρ f These are the densities of the porous composite material and the fluid, respectively. Equation (6) defines the generalized Darcy's law, where p f1 and p f2 These are the two-phase average fluid pressures, η represents the fluid viscosity, and κ represents the average fluid pressure. ij (i, j = 1, 2) represents the permeability coefficient. Formula (7) defines the generalized compressibility law, where ζ int This represents the fluid increment caused by the internal mesoscopic fluid flow. Equation (8) defines the transport law for the internal mesoscopic fluid flow. In Equation (9), the frequency-dependent shear modulus G(ω) is the Hilbert transform of g(ω). Since Pride and Berryman (2003) did not model the frequency dependence of the shear modulus, dispersion related to shear waves is not considered here.

[0064] The constant a in formula (7) ij (i, j = 1, 2) is represented as (Pride et al., 2004):

[0065]

[0066]

[0067] Where v1 and v2 are the volume fractions of the background phase and the heterogeneous phase in the composite material, respectively, and the drainage bulk modulus K of the composite material is... d It is the two-phase drainage bulk modulus K d1 and K d2 The harmonic mean (i.e., 1 / K) d =v1 / K d1 +v2 / K d2), α1 and α2 are the Biot coefficients of the two phases, B1 and B2 are the Skempton coefficients of the two phases, and coefficients R1 and R2 are respectively v2R2=(1-K d1 / K d ) / (1-K d1 / K d2 ).

[0068] The frequency-varying transport coefficient related to mesoscopic fluid flow in formula (8) is defined as follows:

[0069]

[0070] Here, L1 represents the length of the background phase that still retains a fluid pressure gradient in the final stage of equilibrium. V / S describes the volume-to-surface-area ratio. Assuming the heterogeneous phase consists of relatively compliant, coin-shaped inclusions embedded in a relatively rigid background phase, with each inclusion having a radius of a and an aspect ratio of ε, then two geometric parameters L1 can be calculated. 2 =a 2 / 12 and V / S=aε / (2v2).

[0071] Pride et al. (2004) simplified the dual-pore theory into an effective single-pore Biot theory for easier solution. They assumed the heterogeneous phase was completely embedded in the background phase, and the fluid was stationary relative to the heterogeneous rock skeleton, i.e., ▽·q² = 0 in equation (7). Therefore, the effective elastic modulus of the effective Biot medium is...

[0072]

[0073]

[0074]

[0075] Among them, K d * It is the effective drainage bulk modulus of a dual-porosity medium, B * It is the effective Skempton coefficient, K u * It is the effective undrained bulk modulus.

[0076] The spotted saturation model proposed by White (1975) describes the dispersion response caused by wave-induced fluid flow due to the heterogeneity of fluid distribution at the mesoscale. The model is represented by a periodic layered medium, in which the medium consists of alternating stacks of unit layers saturated with two different fluids.

[0077] For a longitudinal wave propagating perpendicular to the medium, its complex elastic modulus E is expressed as:

[0078] E=E0b, (14)

[0079] in,

[0080]

[0081] b = [1 + (I1g1 + I2g2)] -1 ] -1 (16)

[0082]

[0083] Where E0 is the real part of the complex elastic modulus, b is the imaginary part of the complex elastic modulus, p is the fluid saturation, and d is the unit layer thickness.

[0084] For simplicity, the subscript i is omitted. In the real part E0, for each unit layer:

[0085]

[0086]

[0087]

[0088] Among them, E G For P-wave modulus; K u K d K s and K f The bulk modulus, μ, represents the bulk modulus of saturated rock, rock skeleton, solid matrix, and fluid, respectively. d Let B be the shear modulus of the rock skeleton, and B be the Skempton coefficient. Porosity.

[0089] In the imaginary part b of formula (16):

[0090]

[0091]

[0092] Where ω is the frequency, s = ηd 2 / κK E η is viscosity, κ is permeability, and K is effective elastic modulus. E =E d M / E G The longitudinal wave modulus E of the rock skeleton d =K d +(4 / 3)μ d ,in The ratio of longitudinal wave fluid stress to total normal stress, r = αM / E G Biot coefficient α = 1 - K d / Ks .

[0093] The longitudinal wave velocity dispersion is calculated using the following formula:

[0094]

[0095] Among them, complex longitudinal wave velocity ρ is the density of the mottled saturated medium.

[0096] This invention is based on a dual-porosity model describing the heterogeneity of rock structure and a porphyritic saturation model describing the heterogeneity of fluid distribution. It establishes a rock physics modeling method that directly and effectively characterizes the combined effect of dual heterogeneity and the resulting dispersion response of elastic parameters. The equivalent elastic modulus containing two different fluid saturated phases, calculated by formulas (11)-(13) in the dual-porosity rock physics model theory, is used as the input modulus of the porphyritic saturation model. The influence of non-uniform fluid distribution is considered in the context of non-uniform rock structure, thereby establishing a dual heterogeneity model rock physics model. This model can accurately simulate the dispersion response of elastic parameters related to the dual heterogeneity of rock structure and fluid distribution, providing a more comprehensive and reasonable explanation for studying the rock physics mechanism of mesoscale elastic parameter dispersion.

[0097] Figure 1 This is a flowchart for rock physics modeling, addressing the dual heterogeneity of rock structure and fluid distribution. It mainly includes the following steps:

[0098] Step 1: Based on the mineral composition of the rock, calculate the bulk modulus, shear modulus, and density of the solid matrix of the rock using the Hashin-Shtrikman limit theory.

[0099] Step 2: The porous rock skeleton is equivalent to two parts: a background phase with a high degree of consolidation and a heterogeneous phase with a low degree of consolidation. This is used to characterize the heterogeneity of the rock structure. The volume fraction, porosity, permeability, consolidation parameters, etc. of each phase are determined according to the rock properties. Combined with the elastic modulus of the solid matrix calculated in Step 1, the bulk modulus and shear modulus of the two phases of the rock skeleton are calculated based on the effective medium theory.

[0100] Step 3: Assume that the fluid is partially saturated in the rock skeleton to describe the heterogeneity of the fluid distribution. The bulk modulus, shear modulus, density and viscosity coefficient of the two fluids are given respectively.

[0101] Step 4: Using the elastic properties of the solid matrix obtained in Step 1, the properties of the two phases of the rock skeleton obtained in Steps 2 and 3, and the properties of the two-phase fluid given in Step 4, calculate the equivalent elastic modulus of the two different fluid saturated phases based on the dual-pore model.

[0102] Step 5: The elastic properties of the solid matrix obtained in Step 1, the properties of the two-phase fluid given in Step 4, and the properties of the composite phase calculated in Step 6 are used as inputs to the two-phase fluid and skeleton parameters in the porphyritic saturation model. The equivalent elastic moduli of the two different fluid saturated phases calculated in Step 5 are used as input moduli in the porphyritic saturation model. Thus, a rock physics model considering the dual heterogeneity of rock structure and fluid distribution is established, and the dispersion of the rock's elastic parameters is calculated.

[0103] Figure 2 In the simulation by the dual heterogeneity model, the P-wave velocity exhibits two types of dispersion in two frequency bands. The first dispersion is related to the heterogeneity of fluid distribution, and the second dispersion is related to the heterogeneity of rock structure. When the heterogeneous phase content increases from 0.02 to 0.05, the P-wave velocity decreases, but the frequency band in which the dispersion occurs remains unchanged.

[0104] Figure 3 In the simulation by the dual heterogeneity model, the P-wave velocity exhibits two types of dispersion in two frequency bands. The first dispersion is related to the heterogeneity of fluid distribution, and the second dispersion is related to the heterogeneity of rock structure. As the gas saturation increases from 0.1 to 0.7, the P-wave velocity decreases, and the frequency band of the first dispersion, which is related to the heterogeneity of fluid distribution, gradually shifts towards higher frequencies, gradually coinciding with the second dispersion, and the degree of dispersion decreases.

[0105] Figure 4 In the specific condition where the rock skeleton is completely saturated by only one fluid, the heterogeneity of the rock structure is the main cause of dispersion. In this case, the frequency-varying P-wave velocity calculated by the dual heterogeneity model is the same as the result of the dual-pore model. In the specific condition where there is no heterogeneous phase in the rock skeleton, the dispersion is completely controlled by the fluid heterogeneity. In this case, the frequency-varying P-wave velocity calculated by the dual heterogeneity model is the same as the result of the porphyritic saturation model. The above results prove the self-consistency of the established dual heterogeneity model.

[0106] Figure 5 In this study, the experimental data are the bulk modulus dispersion of partially saturated Berea sandstone measured in the laboratory by Chapman et al. (2021). The corresponding bulk modulus dispersion was calculated based on the properties of the rock using a dual heterogeneity model, a porphyritic saturation model, and a dual-porosity model. The calculation results of the dual heterogeneity model showed better agreement with the experimental data.

[0107] Figure 6In this study, the experimental data are Young's modulus dispersions of partially saturated Berea sandstone measured in the laboratory by Chapman et al. (2016). The corresponding Young's modulus dispersions were calculated based on the properties of the rock using a dual heterogeneity model, a porphyritic saturation model, and a dual-porosity model. The calculation results of the dual heterogeneity model showed better agreement with the experimental data.

[0108] This invention provides a rock physics modeling method for the dual heterogeneity of rock structure and fluid distribution. On one hand, the method equates the porous rock skeleton to two parts: a highly consolidated background phase and a poorly consolidated heterogeneous phase, thus characterizing the heterogeneity of the rock structure. On the other hand, it assumes that the fluid in the rock skeleton is partially saturated, thus describing the heterogeneity of the fluid distribution. Specifically, the equivalent elastic modulus of the two different fluid-saturated phases is calculated using a dual-porosity rock physics model, and these are used as input moduli in the porphyritic saturation model. This establishes a rock physics model considering the dual heterogeneity of rock structure and fluid distribution, directly and effectively characterizing the combined effect of the dual heterogeneity and the resulting dispersion response of elastic parameters. Theoretical model calculations are conducted to analyze the influence of the degree of heterogeneity of rock structure and fluid distribution on the dispersion characteristics of elastic parameters. Furthermore, the dual heterogeneity model is calibrated using laboratory measurements from rock core samples, and the parameters in the model are determined. The calibration results demonstrate that this model can more accurately interpret laboratory measurement results compared to conventional models, verifying the advantages and applicability of the model established in this invention.

[0109] The dual heterogeneity rock physics model proposed in this invention can accurately characterize the combined effect of dual heterogeneity of rock structure and fluid distribution and the resulting elastic parameter dispersion response in a direct and effective manner, providing a more comprehensive and reasonable explanation for studying the rock physics mechanism of elastic parameter dispersion at the mesoscale.

[0110] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A petrophysical modeling method of rock structure and fluid distribution dual heterogeneity, characterized in that, Includes the following steps: A. Based on the mineral composition of the rock, calculate the bulk modulus, shear modulus, and density of the solid matrix of the rock using the Hashin-Shtrikman limit theory. B. The porous rock skeleton is equivalent to two parts: a background phase with a high degree of consolidation and a heterogeneous phase with a low degree of consolidation. This is used to characterize the heterogeneity of the rock structure. The volume fraction, porosity, permeability and consolidation parameters of the two phases of the rock skeleton are determined according to the rock properties. C. Based on the elastic modulus of the solid matrix calculated in step A, and the porosity and consolidation parameters of the two phases of the rock skeleton given in step B, calculate the bulk modulus and shear modulus of the two phases of the rock skeleton respectively based on the effective medium theory. D. Assume that the fluid is partially saturated in the rock skeleton to describe the heterogeneity of the fluid distribution. Give the bulk modulus, shear modulus, density and viscosity coefficient of the two fluids respectively. E. Using the elastic properties of the solid matrix obtained in step A, the properties of the two phases of the rock skeleton obtained in steps B and C, and the properties of the two-phase fluid given in step D, calculate the equivalent elastic modulus of the two different fluid saturated phases based on the dual-pore model. F. Calculate the harmonic mean of the rock skeleton properties of the background phase and heterogeneous phase obtained in step B to obtain the properties of the composite phase; G. The elastic properties of the solid matrix obtained in step A, the properties of the two-phase fluid given in step D, and the properties of the composite phase calculated in step F are used as inputs to the two-phase fluid and skeleton parameters in the porphyritic saturation model. The equivalent elastic moduli of the two different fluid saturated phases calculated in step E are used as input moduli in the porphyritic saturation model, thereby establishing a rock physics model that considers the dual heterogeneity of rock structure and fluid distribution. H. Use the dual heterogeneity model established in step G to carry out theoretical model calculations and analyze the influence of the degree of heterogeneity of rock structure and fluid distribution on the dispersion characteristics of elastic parameters. I. The dual heterogeneity model was calibrated using laboratory measurements from core samples to verify the advantages and applicability of the established model.

2. The petrophysical modeling method of rock structure and fluid distribution dual heterogeneity according to claim 1, characterized in that, In step E, the equivalent elastic modulus of the two different fluid saturated phases is calculated based on the dual-pore model: （11） （12） （13） Where, constant a ij ( i , j =1,2) are constants. K d * It is the effective drainage bulk modulus of a dual-porosity medium. B * It is an effective Skempton coefficient. K u * It is the effective undrained bulk modulus.

3. The petrophysical modeling method of rock structure and fluid distribution dual heterogeneity according to claim 2, characterized in that: The equivalent elastic modulus of the two different fluid saturated phases calculated by the dual-pore model includes the dispersion response associated with the non-uniform rock structure.

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