Continental facies shale anisotropic fracture parameter prediction method, device, equipment and medium

Abstract

The invention discloses a continental facies shale anisotropic fracture parameter prediction method and device, equipment and a medium. The method comprises the following steps: testing mineral components, ultrasonic velocity and physical properties of a dry shale sample to obtain the mineral components of the sample, velocity parameters under different confining pressures and porosity; a Voigt-Russ-Hill average method is adopted, and the elastic modulus of a rock matrix is calculated; internal pores of the shale are divided into hard pores and soft pores, and the equivalent elastic modulus of a rock medium is obtained; establishing a relationship among fracture parameters by taking a medium containing hard pores as a background; and carrying out intersection analysis based on the fracture parameters and the anisotropic parameters of the shale, and calculating unknown fracture parameters. According to the method, the distribution characteristics of the micro-pores in the rock are obtained, the relation between the distribution characteristics of the micro-pores and the anisotropy is analyzed, and important theoretical basis and data support are provided for seismic anisotropy exploration, quantitative interpretation and resource evaluation of continental facies shale.

Description

Technical Field

[0001] The present invention relates to the field of shale petrophysics, and more specifically, to a method, apparatus, device and medium for predicting anisotropic fracture parameters of continental shale. Background Art

[0002] Continental shale formations exhibit strong heterogeneity and anisotropy. Scholars at home and abroad have carried out extensive research on rock anisotropy. The complex mineral components and microscopic pore space structures usually exhibit VTI anisotropy. Different from conventional oil and gas reservoirs, shale oil and gas reservoirs have strong anisotropy in their elastic properties due to the oriented arrangement of internal clay, organic matter, and microfractures (the inherent anisotropy of shale), which is also a significant feature of their seismic response and acoustic logging response. Seismic anisotropy plays an important role in the exploration of unconventional oil and gas reservoirs. Systematic petrophysical experiments and theoretical model research can provide important theoretical basis and new method support for it.

[0003] Regarding how to accurately analyze the microscopic structure parameters, which are one of the influencing factors of shale anisotropy, it is currently not lacking. Experimental measurement methods are difficult to accurately obtain the microscopic structure parameters of rocks. Some scholars, based on Zimmerman's method, use Mori-Tanaka theory to obtain microscopic pore parameters from the velocities of dry rocks (hereinafter referred to as the D-Z model), and further use Gassmann's equation to predict the variation relationship between the P-wave and S-wave velocities and pressure of rocks saturated with fluids. In order to obtain the microscopic influencing factors of shale anisotropy, it is necessary to be able to accurately predict the microscopic structure parameters.

[0004] There is currently a need to develop a method for predicting anisotropic fracture parameters of continental shale.

[0005] The information disclosed in the background art section of the present invention is only intended to deepen the understanding of the general background art of the present invention, and should not be regarded as an admission or any form of implication that this information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0006] The present invention proposes a method, apparatus, device and medium for predicting anisotropic fracture parameters of continental shale, which can analyze the relationship between the microscopic pore distribution characteristics and anisotropy by obtaining the microscopic pore distribution characteristics inside the rock, and provide an important theoretical basis and data support for seismic anisotropy exploration, quantitative interpretation and resource evaluation of continental shale.

[0007] In a first aspect, an embodiment of the present disclosure provides a method for predicting anisotropic fracture parameters of continental shale, including:

[0008] Carry out mineral composition, ultrasonic velocity, and physical property tests on dry shale samples to obtain the mineral composition, velocity parameters, and porosity of the samples under different confining pressures;

[0009] Use the Voigt-Reuss-Hill averaging method to calculate the elastic modulus of the rock matrix;

[0010] Divide the internal pores of shale into hard pores and soft pores to obtain the equivalent elastic modulus of the rock medium;

[0011] Taking the medium containing hard pores as the background, establish the relationship between fracture parameters;

[0012] Based on the intersection analysis of the fracture parameters and shale anisotropy parameters, calculate the unknown fracture parameters.

[0013] As a specific implementation manner of the embodiment of the present disclosure, the elastic modulus of the rock matrix is:

[0014]

[0015] where i represents the i-th medium of the mineral phase or pore space, f i represents the volume content of the i-th medium, M i represents the elastic modulus of the i-th medium, M H is the elastic modulus of the rock matrix.

[0016] As a specific implementation manner of the embodiment of the present disclosure, the equivalent elastic modulus of the rock medium is:

[0017]

[0018]

[0019] where K stiff and G stiff are the equivalent bulk modulus and shear modulus of the rock containing only hard pores respectively, K 0 and G 0 are the bulk modulus and shear modulus of the rock particles respectively, φ stiff is the porosity of hard pores in the rock, P and Q are the shape factors of hard pores, which are related to the aspect ratio α of the ellipsoidal pores and the Poisson's ratio ν of the rock particles, ν = (3K 0 - 2G 0 ) / (6K 0 + 2G 0 ), g is only related to the aspect ratio α of hard pores,

[0020] As a specific implementation manner of the embodiments of the present disclosure, taking a medium containing hard pores as the background, establishing the relationships between fracture parameters includes:

[0021] Taking a medium containing hard pores as the background, establishing a relational expression between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock:

[0022] Inverting the aspect ratio of hard pores based on the P-wave and S-wave velocities, obtaining the cumulative fracture density under each pressure, and further obtaining a fitting relational expression between the fracture density and the pressure;

[0023] Dividing the pressure interval equally, establishing a fitting relationship between the fracture aspect ratio and the pressure, and obtaining the fracture aspect ratio corresponding to the pressure;

[0024] Calculating the distribution characteristics of the fracture porosity varying with the fracture density according to the relational expression of the fracture porosity;

[0025] Wherein, the fracture parameters include fracture porosity and fracture density.

[0026] As a specific implementation manner of the embodiments of the present disclosure, the relational expression between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock is:

[0027]

[0028]

[0029] Wherein, K eff , G eff are respectively the equivalent bulk modulus and shear modulus of the rock, ν stiff =(3K stiff -G stiff ) / (6K stiff +2G stiff ) is the Poisson's ratio of the rock containing only hard pores, and Γ is the cumulative fracture density.

[0030] As a specific implementation manner of the embodiments of the present disclosure, the fitting relationship is:

[0031]

[0032] Wherein, is the equivalent Young's modulus under high effective pressure.

[0033] As a specific implementation manner of the embodiments of the present disclosure, the relational expression of the fracture porosity is:

[0034]

[0035] In a second aspect, the embodiments of the present disclosure further provide a device for predicting anisotropic fracture parameters of continental shale, including:

[0036] A testing module that conducts mineral composition, ultrasonic velocity, and physical property tests on dry shale samples to obtain the mineral composition, velocity parameters, and porosity of the samples under different confining pressures;

[0037] A calculation module that calculates the elastic modulus of the rock matrix using the Voigt-Reuss-Hill averaging method;

[0038] A classification module that classifies the internal pores of shale into hard pores and soft pores to obtain the equivalent elastic modulus of the rock medium;

[0039] A modeling module that establishes the relationship between fracture parameters with the medium containing hard pores as the background;

[0040] An intersection module that conducts intersection analysis based on the fracture parameters and shale anisotropy parameters to calculate unknown fracture parameters.

[0041] As a specific implementation manner of the embodiment of the present disclosure, the elastic modulus of the rock matrix is:

[0042]

[0043] where i represents the i-th medium of the mineral phase or pore space, f i represents the volume content of the i-th medium, M i represents the elastic modulus of the i-th medium, M H is the elastic modulus of the rock matrix.

[0044] As a specific implementation manner of the embodiment of the present disclosure, the equivalent elastic modulus of the rock medium is:

[0045]

[0046]

[0047] where K stiff and G stiff are respectively the equivalent bulk modulus and shear modulus of the rock containing only hard pores, K 0 and G 0 are respectively the bulk modulus and shear modulus of the rock particles, φ stiff is the porosity of the hard pores in the rock, P and Q are the shape factors of the hard pores, related to the aspect ratio α of the ellipsoidal pores and the Poisson's ratio ν of the rock particles, ν = (3K 0 - 2G 0 ) / (6K 0 + 2G 0 ), g is only related to the aspect ratio α of the hard pores,

[0048] As a specific implementation manner of the embodiments of the present disclosure, taking a medium containing hard pores as the background, establishing the relationship between fracture parameters includes:

[0049] Taking a medium containing hard pores as the background, establishing the relationship between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock:

[0050] Inverting the aspect ratio of hard pores according to the P-wave and S-wave velocities, obtaining the cumulative fracture density under each pressure, and further obtaining the fitting relationship between the fracture density and the pressure;

[0051] Dividing the pressure interval equally, establishing the fitting relationship between the aspect ratio of fractures and the pressure, and obtaining the aspect ratio of fractures corresponding to the pressure;

[0052] According to the relationship formula of fracture porosity, calculating the distribution characteristics of fracture porosity varying with fracture density;

[0053] Wherein, the fracture parameters include fracture porosity and fracture density.

[0054] As a specific implementation manner of the embodiments of the present disclosure, the relationship between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock is:

[0055]

[0056]

[0057] Wherein, K eff , G eff are respectively the equivalent volume and shear modulus of the rock, ν stiff =(3K stiff -G stiff ) / (6K stiff +2G stiff ) is the Poisson's ratio of the rock containing only hard pores, and Γ is the cumulative fracture density.

[0058] As a specific implementation manner of the embodiments of the present disclosure, the fitting relationship is:

[0059]

[0060] Wherein, is the equivalent Young's modulus under high effective pressure.

[0061] As a specific implementation manner of the embodiments of the present disclosure, the relationship formula of fracture porosity is:

[0062]

[0063] In a third aspect, the embodiments of the present disclosure further provide an electronic device, and the electronic device includes:

[0064] A memory storing executable instructions;

[0065] A processor that runs the executable instructions in the memory to implement the method for predicting anisotropic fracture parameters of continental shale.

[0066] In a fourth aspect, an embodiment of the present disclosure further provides a computer-readable storage medium storing a computer program, which when executed by a processor implements the method for predicting anisotropic fracture parameters of continental shale.

[0067] Its beneficial effects are as follows:

[0068] The method of the present invention aims at the method for predicting the microscopic structure parameters of continental shale reservoirs, obtains the distribution characteristics of microscopic pores inside the rock, has strong practicability, can truly reflect the distribution of reservoir microscopic structure characteristics, can more accurately predict the microscopic structure inside the rock, and the predicted microscopic structure parameters have a good positive correlation with the anisotropic characteristics of shale, clarifying that shale microfractures are one of the factors affecting the anisotropic characteristics of continental shale.

[0069] The method and device of the present invention have other characteristics and advantages, which will be obvious from the accompanying drawings incorporated herein and the subsequent specific embodiments, or will be described in detail in the accompanying drawings incorporated herein and the subsequent specific embodiments, and these drawings and specific embodiments are jointly used to explain the specific principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] By describing the exemplary embodiments of the present invention in more detail in conjunction with the accompanying drawings, the above and other objects, features, and advantages of the present invention will become more obvious. Among them, in the exemplary embodiments of the present invention, the same reference numerals generally represent the same components.

[0071] Figure 1 A flowchart showing the steps of a method for predicting anisotropic fracture parameters of continental shale according to an embodiment of the present invention.

[0072] Figure 2a and Figure 2b Respectively show schematic diagrams of the comparison results of experimental test speed data and model prediction according to an embodiment of the present invention.

[0073] Figure 3a and Figure 3b Respectively show schematic diagrams of the variation relationships between fracture density and fracture content predicted based on the M-T model and the D-Z model and effective pressure according to an embodiment of the present invention.

[0074] Figure 4A schematic diagram showing the variation relationship between the fracture content and the anisotropy parameter according to an embodiment of the present invention.

[0075] Figure 5 A schematic diagram showing the variation relationship between the fracture density and the anisotropy parameter according to an embodiment of the present invention.

[0076] Figure 6 A block diagram showing a prediction device for anisotropic fracture parameters of continental shale according to an embodiment of the present invention.

[0077] Explanation of reference numerals:

[0078] 201, test module; 202, calculation module; 203, classification module; 204, modeling module; 205, intersection module. Detailed implementation manners

[0079] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0080] To facilitate understanding of the solutions and effects of the embodiments of the present invention, six specific application examples are given below. Those skilled in the art should understand that this example is only for facilitating the understanding of the present invention, and any specific details are not intended to limit the present invention in any way.

[0081] Example 1

[0082] Figure 1 A flowchart showing the steps of a method for predicting anisotropic fracture parameters of continental shale according to an embodiment of the present invention.

[0083] As Figure 1 shown, the method for predicting anisotropic fracture parameters of continental shale includes: Step 101, performing mineral composition, ultrasonic velocity, and physical property tests on a dry shale sample to obtain the mineral composition, velocity parameters under different confining pressures, and porosity of the sample; Step 102, calculating the elastic modulus of the rock matrix using the Voigt-Reuss-Hill averaging method; Step 103, dividing the pores inside the shale into hard pores and soft pores to obtain the equivalent elastic modulus of the rock medium; Step 104, establishing the relationship between fracture parameters with the medium containing hard pores as the background; Step 105, performing intersection analysis based on the fracture parameters and the anisotropy parameters of the shale to calculate the unknown fracture parameters.

[0084] In one example, the elastic modulus of the rock matrix is:

[0085]

[0086] where \(i\) represents the \(i\)-th medium of the mineral phase or pore space, and \(f\) i represents the volume content of the \(i\)-th medium, and \(M\) i represents the elastic modulus of the \(i\)-th medium, and \(M\) H is the elastic modulus of the rock matrix.

[0087] In one example, the equivalent elastic modulus of the rock medium is:[[]]

[0088]

[0089]

[0090] where \(K\) stiff and \(G\) stiff are the equivalent bulk and shear moduli of the rock containing only hard pores respectively, and \(K\) 0 and \(G\) 0 are the bulk and shear moduli of the rock grains respectively, \(\varphi\) stiff is the porosity of the hard pores in the rock, and \(P\), \(Q\) are the shape factors of the hard pores, which are related to the aspect ratio \(\alpha\) of the ellipsoidal pores and the Poisson's ratio \(\nu\) of the rock grains. \(\nu=(3K\) 0 - 2G\) 0 ) / (6K\) 0 + 2G\) 0 ) and \(g\) is only related to the aspect ratio \(\alpha\) of the hard pores.

[0091] In one example, taking the medium containing hard pores as the background, establishing the relationships between fracture parameters includes:[[]]

[0092] Taking the medium containing hard pores as the background, establishing the relationship between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock:[[]]

[0093] Inverting the aspect ratio of the hard pores according to the P-wave and S-wave velocities, obtaining the cumulative fracture density at each pressure, and further obtaining the fitting relationship between the fracture density and the pressure;

[0094] Dividing the pressure interval equally, establishing the fitting relationship between the aspect ratio of the fractures and the pressure, and obtaining the aspect ratio of the fractures at the corresponding pressure;

[0095] According to the relationship formula of the fracture porosity, calculating the distribution characteristics of the fracture porosity varying with the fracture density;

[0096] where the fracture parameters include the fracture porosity and the fracture density.

[0097] In one example, the relationship between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock is:[[]]

[0098]

[0099]

[0100] Among them, K eff and G eff are the equivalent volume and shear modulus of the rock respectively, and ν stiff =(3K stiff -G stiff ) / (6K stiff +2G stiff ) is the Poisson's ratio of the rock containing only hard pores, and Γ is the cumulative fracture density.

[0101] In one example, the fitting relationship is:

[0102]

[0103] Among them, is the equivalent Young's modulus under high effective pressure.

[0104] In one example, the relationship formula of the fracture porosity is:

[0105]

[0106] Specifically, first, carry out mineral composition, ultrasonic velocity, and physical property tests on the dry shale sample to obtain the mineral composition, velocity parameters, and porosity of the sample under different confining pressures.

[0107] The Voigt-Reuss-Hill averaging method is used to calculate the elastic modulus of the rock matrix, and the theoretical estimated value can be obtained. The specific formula is as follows:

[0108]

[0109] Among them, i represents the i-th medium of the mineral phase or pore space, and f i represents the volume content of the i-th medium, and M i represents the elastic modulus of the i-th medium.

[0110] The pores inside the shale are divided into hard pores and soft pores. Based on the Mori-Tanaka theory, the relationship between the elastic modulus of the rock and the microscopic pore structure is established. Then, the equivalent elastic modulus of the rock medium is:

[0111]

[0112]

[0113] Among them, K stiff and G stiffare the equivalent volume and shear modulus of the rock containing only hard pores (intergranular pores), respectively, K 0 and G 0 are the volume and shear modulus of the rock particles, respectively, φ stiff is the porosity of the hard pores in the rock, and P and Q are the shape factors of the hard pores, which are related to the aspect ratio α of the ellipsoidal pores and the Poisson's ratio ν of the rock particles, and are respectively defined as:

[0114]

[0115]

[0116] where ν = (3K 0 - 2G 0 ) / (6K 0 + 2G 0 ), and g is only related to the aspect ratio α of the hard pores, and its expression is:

[0117]

[0118] Taking the medium containing hard pores as the background and considering the influence of fractures on the elastic properties, the relationship between the equivalent elastic modulus of the rock and the cumulative fracture density of the rock (abbreviated as the M-T model) is:

[0119]

[0120]

[0121] where K eff , G eff are the equivalent volume and shear modulus of the rock, respectively, ν stiff = (3K stiff - G stiff ) / (6K stiff + 2G stiff ) is the Poisson's ratio of the rock containing only hard pores, and Γ is the cumulative fracture density.

[0122] Since the soft pores (fractures) are approximately completely closed under high effective pressure, only hard pores exist in the rock. Therefore, the aspect ratio of the hard pores in the rock can be inversely calculated by combining the longitudinal and transverse wave velocities of the rock measured in the laboratory under high effective pressure with formula (1).

[0123] The pressure dependence of the effective modulus is closely related to the fracture density. When the fracture density is given, the elastic modulus can be used to obtain the cumulative fracture density at each pressure by formulas (4) and (5).

[0124] Using the variation relationship between the fracture density and the effective pressure where Γ i is the initial fracture density when the effective pressure is 0, is a pressure constant of the same order of magnitude as p. Combining the variation relationship of fracture density with pressure, the fitting relationship between fracture density and pressure can be calculated for calculating fracture porosity.

[0125] Divide the pressure range into n equal parts. Using the relationship between fracture aspect ratio and pressure, the corresponding fracture aspect ratio under pressure is obtained, and the relationship between the two is:

[0126]

[0127] where is the equivalent Young's modulus under high effective pressure.

[0128] Then through the relationship formula of fracture porosity Abbreviation: D-Z model, calculate the distribution characteristics of fracture porosity varying with fracture density. Finally, based on the cross-analysis of the obtained fracture parameters and shale anisotropic parameters, calculate the unknown fracture parameters.

[0129] Example 2

[0130] The present invention also provides a device for predicting anisotropic fracture parameters of continental shale, including:

[0131] A testing module conducts mineral composition, ultrasonic velocity, and physical property tests on dry shale samples to obtain the mineral composition, velocity parameters, and porosity of the samples under different confining pressures;

[0132] A calculation module calculates the elastic modulus of the rock matrix using the Voigt-Reuss-Hill averaging method;

[0133] A classification module classifies the internal pores of shale into hard pores and soft pores to obtain the equivalent elastic modulus of the rock medium;

[0134] A modeling module establishes the relationship between fracture parameters with the medium containing hard pores as the background;

[0135] A cross module conducts cross-analysis based on fracture parameters and shale anisotropic parameters to calculate unknown fracture parameters.

[0136] In an example, the elastic modulus of the rock matrix is:

[0137]

[0138] where i represents the i-th medium of the mineral phase or pore space, f i represents the volume content of the i-th medium, M i represents the elastic modulus of the i-th medium, M H is the elastic modulus of the rock matrix.

[0139] In one example, the equivalent elastic modulus of the rock medium is:

[0140]

[0141]

[0142] where K stiff and G stiff are respectively the equivalent bulk modulus and shear modulus of the rock containing only hard pores, K 0 and G 0 are respectively the bulk modulus and shear modulus of the rock particles, φ stiff is the porosity of the hard pores in the rock, P and Q are the shape factors of the hard pores, which are related to the aspect ratio α of the ellipsoidal pores and the Poisson's ratio ν of the rock particles, ν = (3K 0 - 2G 0 ) / (6K 0 + 2G 0 ), and g is only related to the aspect ratio α of the hard pores,

[0143] In one example, taking the medium containing hard pores as the background, establishing the relationships between fracture parameters includes:

[0144] Taking the medium containing hard pores as the background, establishing the relationship between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock:

[0145] Inverting the aspect ratio of the hard pores according to the P-wave and S-wave velocities, obtaining the cumulative fracture density at each pressure, and further obtaining the fitting relationship between the fracture density and the pressure;

[0146] Dividing the pressure interval equally, establishing the fitting relationship between the aspect ratio of the fractures and the pressure, and obtaining the aspect ratio of the fractures at the corresponding pressure;

[0147] According to the relationship formula of the fracture porosity, calculating the distribution characteristics of the fracture porosity varying with the fracture density;

[0148] where the fracture parameters include the fracture porosity and the fracture density.

[0149] In one example, the relationship between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock is:

[0150]

[0151]

[0152] where K eff 、G effare the equivalent volume and shear modulus of the rock, respectively, ν stiff =(3K stiff -G stiff ) / (6K stiff +2G stiff ) is the Poisson's ratio of the rock containing only hard pores, and Γ is the cumulative fracture density.

[0153] In one example, the fitting relationship is:

[0154]

[0155] where is the equivalent Young's modulus under high effective pressure.

[0156] In one example, the relationship formula of fracture porosity is:

[0157]

[0158] Specifically, first, carry out mineral composition, ultrasonic velocity, and physical property tests on the dry shale sample to obtain the mineral composition, velocity parameters, and porosity of the sample under different confining pressures.

[0159] The elastic modulus of the rock matrix is calculated using the Voigt - Reuss - Hill averaging method, and the theoretical estimated value can be obtained. The specific formula is as follows:

[0160]

[0161] where i represents the ith medium of the mineral phase or pore space, f i represents the volume content of the ith medium, and M i represents the elastic modulus of the ith medium.

[0162] The pores inside the shale are divided into hard pores and soft pores. Based on the Mori - Tanaka theory, the relationship between the elastic modulus of the rock and the microscopic pore structure is established. Then, the equivalent elastic modulus of the rock medium is:

[0163]

[0164]

[0165] where K stiff and G stiff are the equivalent volume and shear modulus of the rock containing only hard pores (intergranular pores), respectively. K 0 and G 0 are the volume and shear modulus of the rock particles, respectively, and φ stiffis the porosity of hard pores in the rock, and P and Q are the shape factors of the hard pores, which are related to the aspect ratio α of the ellipsoidal pores and the Poisson's ratio ν of the rock grains, and are respectively defined as:

[0166]

[0167]

[0168] where ν = (3K 0 - 2G 0 ) / (6K 0 + 2G 0 ), and g is only related to the aspect ratio α of the hard pores, and its expression is:

[0169]

[0170] Taking the medium containing hard pores as the background and considering the influence of fractures on the elastic properties, the relationship between the equivalent elastic modulus of the rock and the cumulative fracture density of the rock (abbreviated as the M-T model) is:

[0171]

[0172]

[0173] where K eff , G eff are respectively the equivalent bulk and shear moduli of the rock, ν stiff = (3K stiff - G stiff ) / (6K stiff + 2G stiff ) is the Poisson's ratio of the rock containing only hard pores, and Γ is the cumulative fracture density.

[0174] Since the soft pores (fractures) are approximately completely closed under high effective pressure, only hard pores exist in the rock. Therefore, the aspect ratio of the hard pores in the rock can be inversely calculated by combining the longitudinal and transverse wave velocities of the rock measured in the laboratory under high effective pressure with formula (1).

[0175] The pressure dependence of the effective modulus is closely related to the fracture density. When the fracture density is given, the elastic modulus can be used to obtain the cumulative fracture density at each pressure with formulas (4) and (5).

[0176] Using the variation relationship between the fracture density and the effective pressure where Γ i is the initial fracture density when the effective pressure is 0, is a pressure constant of the same order of magnitude as p. Combining the variation relationship of the fracture density with pressure, the fitting relationship between the fracture density and pressure can be calculated for calculating the fracture porosity.

[0177] Divide the pressure range into n equal parts. Using the relationship between the fracture aspect ratio and pressure, obtain the corresponding fracture aspect ratio under pressure. The relationship between the two is as follows:

[0178]

[0179] Wherein, is the equivalent Young's modulus under high effective pressure.

[0180] Then, through the relationship formula of fracture porosity Abbreviated as the D-Z model, calculate the distribution characteristics of fracture porosity varying with fracture density. Finally, based on the intersection analysis of the fracture parameters and shale anisotropic parameters obtained above, calculate the unknown fracture parameters.

[0181] Example 3

[0182] For the continental shale core data in a certain area, use the D-Z model and M-T model to invert the internal micro-pore structure parameters of the shale, and the prediction results are in good agreement with the measured data.

[0183] Figure 2a and Figure 2b respectively show the schematic diagrams of the comparison results between the experimental test velocity data and the model prediction according to an embodiment of the present invention. It can be concluded that the experimental test velocity results and the prediction results of the M-T model have good consistency.

[0184] Figure 3a and Figure 3b respectively show the schematic diagrams of the variation relationships between the fracture density and fracture content predicted based on the M-T model and D-Z model and the effective pressure according to an embodiment of the present invention. The results show that the fracture density and fracture content decrease with the increase of pressure.

[0185] Figure 4 Shows the schematic diagram of the variation relationship between the fracture content and the anisotropic parameter according to an embodiment of the present invention.

[0186] Figure 5 Shows the schematic diagram of the variation relationship between the fracture density and the anisotropic parameter according to an embodiment of the present invention.

[0187] It can be obtained that with the increase of fracture density / fracture content, the anisotropic parameter shows an increasing trend, indicating that micro-fractures are also one of the factors affecting the anisotropic characteristics of continental shale.

[0188] The present invention combines the M-T model and the D-Z type to obtain the characteristics of the internal microscopic pore distribution of rocks, further analyzes the relationship between the microscopic pore distribution characteristics and anisotropy, and provides an important theoretical basis and data support for seismic anisotropy exploration, quantitative interpretation, and resource evaluation of continental shales.

[0189] Example 4

[0190] Figure 6 The block diagram of a device for predicting anisotropic fracture parameters of continental shale according to an embodiment of the present invention is shown.

[0191] As Figure 6 shown, the device for predicting anisotropic fracture parameters of continental shale includes:

[0192] A test module 201 that conducts mineral composition, ultrasonic velocity, and physical property tests on a dry shale sample to obtain the mineral composition, velocity parameters under different confining pressures, and porosity of the sample;

[0193] A calculation module 202 that calculates the elastic modulus of the rock matrix using the Voigt-Reuss-Hill averaging method;

[0194] A classification module 203 that classifies the internal pores of the shale into hard pores and soft pores to obtain the equivalent elastic modulus of the rock medium;

[0195] A modeling module 204 that establishes the relationship between fracture parameters with the medium containing hard pores as the background;

[0196] An intersection module 205 that conducts intersection analysis based on fracture parameters and shale anisotropic parameters to calculate unknown fracture parameters.

[0197] As an optional solution, the elastic modulus of the rock matrix is:

[0198]

[0199] where i represents the i-th medium of the mineral phase or pore space, f i represents the volume content of the i-th medium, M i represents the elastic modulus of the i-th medium, M H is the elastic modulus of the rock matrix.

[0200] As an optional solution, the equivalent elastic modulus of the rock medium is:

[0201]

[0202]

[0203] where K stiff and Gstiff are the equivalent volume and shear modulus of the rock containing only hard pores, respectively, K 0 and G 0 are the volume and shear modulus of the rock particles, respectively, φ stiff is the porosity of the hard pores in the rock, P and Q are the shape factors of the hard pores, which are related to the aspect ratio α of the ellipsoidal pores and the Poisson's ratio ν of the rock particles, ν = (3K 0 - 2G 0 ) / (6K 0 + 2G 0 ), g is only related to the aspect ratio α of the hard pores,

[0204] As an alternative, taking the medium containing hard pores as the background, establishing the relationships between fracture parameters includes:

[0205] Taking the medium containing hard pores as the background, establishing the relationship between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock:

[0206] Inverting the aspect ratio of the hard pores according to the P-wave and S-wave velocities, obtaining the cumulative fracture density at each pressure, and further obtaining the fitting relationship between the fracture density and the pressure;

[0207] Dividing the pressure interval equally, establishing the fitting relationship between the fracture aspect ratio and the pressure, and obtaining the fracture aspect ratio at the corresponding pressure;

[0208] According to the relationship formula of the fracture porosity, calculating the distribution characteristics of the fracture porosity changing with the fracture density;

[0209] Among them, the fracture parameters include the fracture porosity and the fracture density.

[0210] As an alternative, the relationship between the equivalent elastic modulus of the rock medium and the cumulative fracture density of the rock is:

[0211]

[0212]

[0213] Among them, K eff , G eff are the equivalent volume and shear modulus of the rock, respectively, ν stiff = (3K stiff - G stiff ) / (6K stiff + 2G stiff ) is the Poisson's ratio of the rock containing only hard pores, and Γ is the cumulative fracture density.

[0214] As an alternative, the fitting relationship is:

[0215]

[0216] Among them, is the equivalent Young's modulus under high effective pressure.

[0217] As an alternative, the relationship of fracture porosity is:

[0218]

[0219] Example 5

[0220] This embodiment provides an electronic device, which includes: a memory storing executable instructions; a processor that runs the executable instructions in the memory to implement the above-mentioned prediction method for anisotropic fracture parameters of continental shale.

[0221] The electronic device according to an embodiment of the present disclosure includes a memory and a processor.

[0222] This memory is used to store non-temporary computer-readable instructions. Specifically, the memory may include one or more computer program products, and the computer program products may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory, etc. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc.

[0223] The processor may be a central processing unit (CPU) or other forms of processing units with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions. In an embodiment of the present disclosure, the processor is used to run the computer-readable instructions stored in the memory.

[0224] Those skilled in the art should understand that, in order to solve the technical problem of how to obtain good user experience effects, this embodiment may also include well-known structures such as communication buses and interfaces, and these well-known structures should also be included in the protection scope of the present disclosure.

[0225] For the detailed description of this embodiment, reference may be made to the corresponding descriptions in the foregoing embodiments, and details will not be repeated here.

[0226] Example 6

[0227] This embodiment provides a computer-readable storage medium, which stores a computer program, and when the computer program is executed by a processor, the above-mentioned prediction method for anisotropic fracture parameters of continental shale is implemented.

[0228] A computer-readable storage medium according to an embodiment of the present disclosure stores non-transitory computer-readable instructions. When the non-transitory computer-readable instructions are run by a processor, all or part of the steps of the methods of the various embodiments of the present disclosure described above are executed.

[0229] The above computer-readable storage medium includes but is not limited to: optical storage media (e.g., CD-ROMs and DVDs), magneto-optical storage media (e.g., MOs), magnetic storage media (e.g., magnetic tapes or external hard drives), media with built-in rewritable non-volatile memories (e.g., memory cards), and media with built-in ROMs (e.g., ROM cartridges).

[0230] Those skilled in the art should understand that the purpose of the above description of the embodiments of the present invention is only to exemplarily illustrate the beneficial effects of the embodiments of the present invention, and is not intended to limit the embodiments of the present invention to any of the examples given.

[0231] The various embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is also not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for predicting anisotropic fracture parameters of continental shale. It is characterized in that include: The dried shale samples were subjected to mineral composition, ultrasonic velocity, and physical property tests to obtain the mineral composition, velocity parameters under different confining pressures, and porosity of the samples; The elastic modulus of the rock matrix was calculated using the Voigt-Reuss-Hill averaging method; The internal pores of shale are divided into hard pores and soft pores to obtain the equivalent elastic modulus of the rock medium; The relationship between fracture parameters is established in the context of a medium containing hard pores; Based on the intersection analysis of the fracture parameters and shale anisotropy parameters, unknown fracture parameters are calculated.

2. The method for predicting anisotropic fracture parameters of continental shale according to claim 1, in, The elastic modulus of the rock matrix is: Where i represents the mineral phase or the i-th medium in the pore space, and f i represents the volume content of the ith medium, M i represents the elastic modulus of the ith medium, M H is the elastic modulus of the rock matrix.

3. The method for predicting anisotropic fracture parameters of continental shale according to claim 1, in, The equivalent elastic modulus of the rock medium is: Among them, K stiff and G stiff are the equivalent volume and shear moduli of the rock containing only hard pores, K 0 and G 0 are the volume and shear moduli of rock particles, φ stiff is the porosity of hard pores in rocks, P and Q are the shape factors of hard pores, which are related to the aspect ratio α of ellipsoidal pores and the Poisson’s ratio ν of rock particles. ν=(3K 0 -2G 0 ) / (6K 0 +2G 0 ), g is only related to the aspect ratio α of the hard pores, 4. The method for predicting anisotropic fracture parameters of continental shale according to claim 1, in, In the context of a medium containing hard pores, the relationship between fracture parameters is established including: Taking the medium containing hard pores as the background, the relationship between the equivalent elastic modulus of rock medium and the cumulative crack density of rock is established: The hard pore aspect ratio is inverted according to the P- and S-wave velocities to obtain the cumulative fracture density at each pressure, and then the fitting relationship between fracture density and pressure is obtained; Divide the pressure interval into equal parts, establish the fitting relationship between the crack aspect ratio and pressure, and obtain the crack aspect ratio under the corresponding pressure; According to the relationship between fracture porosity, the distribution characteristics of fracture porosity changing with fracture density are calculated; The fracture parameters include fracture porosity and fracture density.

5. The method for predicting anisotropic fracture parameters of continental shale according to claim 4, in, The relationship between the equivalent elastic modulus of rock medium and the cumulative crack density of rock is: Among them, K eff , G eff are the equivalent volume and shear moduli of rock, ν stiff =(3K stiff -G stiff ) / (6K stiff +2G stiff ) is the Poisson's ratio of the rock containing only hard pores, and Γ is the cumulative fracture density.

6. The method for predicting anisotropic fracture parameters of continental shale according to claim 4, in, The fitting relationship is: in, is the equivalent Young's modulus at high effective pressure.

7. The method for predicting anisotropic fracture parameters of continental shale according to claim 4, in, The relationship between fracture porosity and porosity is:

8. A device for predicting anisotropic fracture parameters of continental shale, It is characterized in that include: The test module conducts mineral composition, ultrasonic velocity, and physical property tests on dry shale samples to obtain the mineral composition, velocity parameters under different confining pressures, and porosity of the samples; The calculation module uses the Voigt-Reuss-Hill averaging method to calculate the elastic modulus of the rock matrix; The classification module divides the internal pores of shale into hard pores and soft pores to obtain the equivalent elastic modulus of the rock medium; A modeling module that establishes the relationship between fracture parameters in the context of a medium containing hard pores; The intersection module performs intersection analysis based on the fracture parameters and shale anisotropy parameters to calculate unknown fracture parameters.

9. An electronic device, It is characterized in that The electronic device comprises: A memory storing executable instructions; A processor, wherein the processor runs the executable instructions in the memory to implement the method for predicting anisotropic fracture parameters of continental shale according to any one of claims 1 to 7.

10. A computer-readable storage medium, It is characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for predicting anisotropic fracture parameters of continental shale according to any one of claims 1 to 7 is implemented.

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