Anisotropic rock physical modeling method

Abstract

The invention provides an anisotropic rock physical modeling method, which belongs to the technical field of rock physical modeling in oil exploration, and comprises the following steps: preprocessing logging information; using logging information to interpret attributes of a target interval; establishing a matrix model; calculating an included angle between the trend of the crack and the maximum principal stress direction by applying imaging logging information; the method comprises the following steps: establishing an anisotropic influence factor model by applying dipole sound wave data and evaluating influence conditions of different included angles on shear wave velocity; establishing a dry rock model; establishing a pore fluid model; on the basis of the dry rock model and the elastic model of the pore fluid, an anisotropic saturated rock model is established. According to the method, the anisotropic saturated rock model is corrected by introducing the influence factors, the influence of the difference between the stress directions of different layers of different well points and the fracture occurrence on the shear wave speed is eliminated, and the distribution rule of the elastic parameters of the reservoir under the formation anisotropy can be truly reflected.

Description

Technical Field

[0001] The invention belongs to the field of rock physics modeling in petroleum exploration, and in particular relates to an anisotropic rock physics modeling method. Background Art

[0002] Shear wave prediction is a necessary parameter for reservoir inversion and rock mechanics analysis. Conventional fractured rock physics modeling mainly includes the Hudson model and the linear sliding theory model. However, the model generally requires that the fracture density should not be greater than 0.1, or that the fractures need to be spaced apart from each other, which makes it less applicable to areas with developed network fractures.

[0003] In the strong stress area, cracks are developed, and the anisotropy of the formation is not only affected by the occurrence of cracks, but also by the direction of the principal stress. The shear wave velocity is a polarized wave, which is sensitive to the occurrence of cracks and strong stress. The occurrence of cracks and the direction of stress have a great influence on the shear wave velocity, which leads to the disordered and distorted distribution of elastic parameters when the longitudinal and shear wave velocity ratios measured by dipole acoustic wave data are used to analyze the lithology and physical properties of the reservoir. It is very different from the distribution of elastic parameters of conventional reservoirs and cannot be effectively used in subsequent inversion work.

[0004] In some mountainous areas, anticline fractures are well developed. When the P-wave and S-wave velocity ratios measured by dipole acoustic wave data are used to analyze the lithology and physical properties of the reservoir, the elastic parameter distribution law is disordered and distorted, which is inconsistent with the actual elastic parameter distribution law and is significantly different from that of the real elastic parameter distribution law, and cannot be effectively used in subsequent inversion work.

[0005] From the perspective of the fractures picked up by imaging logging (FMI), the anticline has a multi-stage fracture system, including fractures in the stress state of reverse fault and strike-slip fault. The fracture occurrence (inclination and strike) at different well points varies greatly, and there are also certain differences in the stress direction. Combined with the propagation mode of shear waves as polarized waves, it is analyzed that the fracture occurrence and stress direction are the main reasons for the disorder of elastic parameters.

[0006] Chinese invention patent CN111273341A discloses a rock physics modeling method for fractured reservoirs based on the spatial distribution of fractures, and proposes a modeling method for the influence of different fracture densities and different fracture spatial distributions on elastic wave velocity. Its advantage is that the fracture spatial distribution is taken into account in rock physics modeling as an independent physical parameter other than fracture density. However, this fracture geological model cannot specifically solve the problem that the distribution law of the elastic parameters of the target layer measured in the strong stress area is quite different from the actual distribution law of the elastic parameters. Summary of the invention

[0007] In view of the problems existing in the above-mentioned prior art, the present invention provides an anisotropic rock physics modeling method. The technical problem to be solved by the present invention is to eliminate the influence of the differences in stress directions and fracture occurrences in different layers at different well points on the shear wave velocity, truly reflect the distribution law of reservoir elastic parameters under formation anisotropy, and provide basic data support for subsequent reservoir inversion, rock brittleness evaluation, etc.

[0008] In order to solve the above technical problems, the present invention provides an anisotropic rock physics modeling method, comprising the following steps:

[0009] Step S1: Obtain the attributes of the target layer segment;

[0010] Step S2: using the properties of the target layer to establish a matrix model;

[0011] Step S3: using imaging logging data, calculating the angle between the crack strike and the maximum principal stress direction;

[0012] Step S4: using dipole acoustic wave data, by evaluating the influence of different angles on shear wave velocity, an anisotropic influence factor model is established;

[0013] Step S5: using the matrix model and the anisotropic influencing factor model to establish a dry rock model;

[0014] Step S6: establishing an elastic model of pore fluid;

[0015] Step S7: Based on the dry rock model and the elastic model of the pore fluid, an anisotropic saturated rock model is established.

[0016] Furthermore, the step S1 includes the following steps:

[0017] Step H1: pre-processing the logging data;

[0018] Step H2: Use logging data to interpret the properties of the target layer.

[0019] Furthermore, in the step H1, the preprocessing includes well curve environment correction and well curve standardization.

[0020] Furthermore, in step H2, the properties of the target layer segment include mud content, porosity, saturation and fracture density.

[0021] Furthermore, in step S2, the Wyllie time-averaged equation is applied to establish the rock matrix elastic modulus and matrix density as follows:

[0022]

[0023]

[0024]

[0025] Among them, Vp ma is the longitudinal wave velocity of rock foundation, Vs ma is the rock matrix shear wave velocity, φ is the porosity, V clay is the clay content, Vp quartz is the quartz longitudinal wave velocity, Vs quartz is the quartz shear wave velocity, Vp clay is the clay longitudinal wave velocity, Vs clay is the clay shear wave velocity, ρ ma is the matrix density, ρ quartz is the density of quartz, ρ clay is the density of clay.

[0026] Furthermore, in step S3, imaging logging data is used to identify induced fractures and structural fractures respectively, the maximum principal stress direction is determined by the induced fractures, the distribution of the inclination angle and strike of the structural fractures is statistically analyzed, and a relationship diagram between the inclination angle and the longitudinal wave and the shear wave is prepared to calculate the angle between the strike of the fracture and the maximum principal stress direction.

[0027] Furthermore, in step S4, the influence factor of crack density on the angle is established by using dipole acoustic wave data. By evaluating the influence of different angles on the shear wave velocity, the threshold Q of the angle is analyzed and obtained. The calculation formula of the anisotropic influence factor model is as follows:

[0028]

[0029]

[0030] Δ=Δ2-Δ1

[0031] Among them, Δ1 is the change of shear wave velocity with crack density when the angle is less than Q, Δ2 is the change of shear wave velocity with crack density when the angle is greater than Q; Δ is the difference in the influence of the shear wave velocity when the angle is greater than Q and when the angle is less than Q; FDI is the crack density; α is the influence factor of crack density on the angle when the angle is less than Q, and β is the influence factor of crack density on the angle when the angle is greater than Q.

[0032] Furthermore, the influence factor of the crack density on the angle is obtained by fitting the shear wave velocity and crack density of the dipole acoustic wave data.

[0033] Furthermore, in step S5, the matrix model and the anisotropic influencing factor model are used to establish the elastic modulus of dry rock under the constraints of the maximum principal stress direction and the crack orientation.

[0034] Furthermore, using the Kustor-Toksoz formula, the elastic modulus of dry rock is calculated as:

[0035]

[0036]

[0037] in,

[0038]

[0039] μ ma =ρ ma (Vs ma +Δ) 2

[0040] Where K dry is the bulk modulus of dry rock, μ dry is the shear modulus of dry rock, K ma is the bulk modulus of rock matrix after stress and fracture constraints, μ ma is the shear modulus of the rock matrix after stress and fracture constraint, A is the pore flatness of sandstone, and B is the pore flatness of mudstone.

[0041] Furthermore, in step S6, an elastic model of pore fluid under different temperature and pressure environments is established.

[0042] Furthermore, in step S6, the bulk modulus and fluid density of the equivalent pore fluid are calculated using the Wodd equation according to the saturation information:

[0043]

[0044] ρ f =S w ρ w +(1-S w )ρ h

[0045] Where K f is the bulk modulus of the fluid, ρ f is the fluid density, S w is water saturation, K w is the bulk modulus of formation water, K h is the bulk modulus of hydrocarbons, ρ w is the formation water density, ρ h is the density of hydrocarbons.

[0046] Furthermore, in step S7, based on the dry rock model and the elastic model of the pore fluid, the elastic modulus of the anisotropic saturated rock is established:

[0047]

[0048] μ sat =μ dry

[0049] ρ sat =φρ f +(1-φ)ρ ma

[0050] Where K sat is the bulk modulus of saturated rock, μ sa t is the shear modulus of saturated rock, ρ sat is the saturated rock density.

[0051] The present invention provides an anisotropic rock physics modeling method, which introduces an influencing factor to correct the anisotropic saturated rock model, thereby eliminating the influence of the differences in stress directions and fracture occurrences in different layers at different well points on the shear wave velocity. The shear wave velocity is obtained by using the anisotropic saturated rock model, and the distribution law of elastic parameters is obtained by using the shear wave velocity. The distribution law of reservoir elastic parameters under formation anisotropy can be truly reflected, and basic data support can be provided for subsequent reservoir inversion, rock brittleness evaluation, etc.

[0052] The anisotropic rock physics modeling method of the present invention is mainly a fine rock physics modeling technology for the situation where the elastic parameters measured in a strong stress environment and a fractured reservoir are disordered and cannot guide the subsequent reservoir inversion, and can provide a prediction mechanism for the subsequent reservoir inversion.

[0053] The present invention performs dual constraints and corrections on the anisotropy of rocks in terms of the crack orientation and the principal stress direction, and restores the true elastic parameters of the reservoir. In the application process, it is necessary to consider the angle between the crack orientation and the maximum principal stress, combine imaging logging and dipole acoustic wave data, consider the influence of different angles on the shear wave velocity, establish different influencing factors and apply them to the modeling, thereby eliminating the influence of the crack occurrence and stress direction differences on the elastic parameters, and can effectively identify the lithology and fluid of reservoirs with strong stress environments and developed cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a flow chart of an anisotropic rock physics modeling method of the present invention.

[0055] Figure 2 It is a schematic diagram of the induced fracture trend (N-north, E-east, S-south, W-west) of an anisotropic rock physics modeling method of the present invention.

[0056] Figure 3 It is a schematic diagram of structural fracture strike (N-north, E-east, S-south, W-west) of an anisotropic rock physics modeling method of the present invention.

[0057] Figure 4 It is a schematic diagram of structural fracture inclination angle of an anisotropic rock physics modeling method of the present invention.

[0058] Figure 5 It is a schematic diagram of the effect of angle on shear wave velocity in an anisotropic rock physics modeling method of the present invention, and the arrows in the figure represent the fitting trend of the sample points.

[0059] Figure 6 It is a schematic diagram of the effect of angle on shear wave velocity in an anisotropic rock physics modeling method of the present invention, and the arrows in the figure represent the fitting trend of the sample points.

[0060] Figure 7 It is a schematic diagram of elastic parameter distribution obtained by applying dipole acoustic wave data to the existing technical model.

[0061] Figure 8 It is a schematic diagram of elastic parameter distribution obtained by using the anisotropic saturated rock model of the present invention. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0065] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0066] In order to better understand the purpose, structure and function of the present invention, an anisotropic rock physics modeling method of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0067] Embodiment 1:

[0068] like Figure 1 As shown, the present invention provides an anisotropic rock physics modeling method, comprising the following steps:

[0069] Step S1: Obtain the attributes of the target layer segment;

[0070] Step S2: using the properties of the target layer to establish a matrix model;

[0071] Step S3: using imaging logging data, calculating the angle between the crack strike and the maximum principal stress direction;

[0072] Step S4: using dipole acoustic wave data, by evaluating the influence of different angles on shear wave velocity, an anisotropic influence factor model is established;

[0073] Step S5: using the matrix model and the anisotropic influencing factor model to establish a dry rock model;

[0074] Step S6: establishing an elastic model of pore fluid;

[0075] Step S7: Based on the dry rock model and the elastic model of the pore fluid, an anisotropic saturated rock model is established.

[0076] Embodiment 2:

[0077] like Figure 1 As shown, the present invention provides an anisotropic rock physics modeling method, comprising the following steps:

[0078] Step S1: Obtain the attributes of the target layer segment;

[0079] Step S2: using the properties of the target layer to establish a matrix model;

[0080] Step S3: using imaging logging data, calculating the angle between the crack strike and the maximum principal stress direction;

[0081] Step S4: using dipole acoustic wave data, by evaluating the influence of different angles on shear wave velocity, an anisotropic influence factor model is established;

[0082] Step S5: using the matrix model and the anisotropic influencing factor model to establish a dry rock model;

[0083] Step S6: establishing an elastic model of pore fluid;

[0084] Step S7: Based on the dry rock model and the elastic model of the pore fluid, an anisotropic saturated rock model is established.

[0085] The difference between this embodiment and the first embodiment is that:

[0086] The step S1 includes the following steps:

[0087] Step H1: pre-processing the logging data;

[0088] Step H2: Use logging data to interpret the properties of the target layer.

[0089] In the step H1, the preprocessing includes well curve environment correction and well curve standardization;

[0090] In step H2, the properties of the target layer include lithology (shale content), physical properties (porosity), saturation and fracture density;

[0091] In step S2, the Wyllie time-averaged equation is applied to establish the rock matrix elastic modulus and matrix density:

[0092]

[0093]

[0094]

[0095] Where Vp ma is the longitudinal wave velocity of rock foundation, Vs ma is the rock matrix shear wave velocity, φ is the porosity, V clay is the clay content, Vp quartz is the quartz longitudinal wave velocity, Vs quartz is the quartz shear wave velocity, Vp clay is the clay longitudinal wave velocity, Vs clay is the clay shear wave velocity, ρ ma is the matrix density, ρ quartz is the density of quartz, ρ clay is the density of clay.

[0096] like Figure 2 , Figure 3 and Figure 4 The well logging imaging data shown in the figure, in the step S3, the imaging well logging data is used to identify the induced fractures and the structural fractures respectively, the maximum principal stress direction is determined by the induced fractures, the inclination angle and the strike distribution of the structural fractures are statistically analyzed, and a relationship diagram between the strike and the longitudinal wave and the shear wave is prepared to realize the calculation of the angle between the strike of the fracture and the maximum principal stress direction;

[0097] In step S4, the influence factor of crack density on the angle is established by using the dipole acoustic wave data. By evaluating the influence of different angles on the shear wave velocity, the threshold value A of the angle is analyzed and obtained. The influence factor is obtained by fitting the shear wave velocity and crack density of the dipole acoustic wave data. The calculation formula of the anisotropic influence factor model is as follows:

[0098]

[0099]

[0100] Δ=Δ2-Δ1

[0101] Among them, Δ1 is the change of shear wave velocity with crack density when the angle is less than Q, Δ2 is the change of shear wave velocity with crack density when the angle is greater than Q; Δ is the difference in the influence of the shear wave velocity when the angle is greater than Q and when the angle is less than Q; FDI is the crack density; α is the influence factor of crack density on the angle when the angle is less than Q, and β is the influence factor of crack density on the angle when the angle is greater than Q.

[0102] Step S5: Using the Kustor-Toksoz formula, establish the elastic modulus of dry rock under the constraints of the maximum principal stress direction and the crack orientation:

[0103]

[0104]

[0105] in,

[0106]

[0107] μ ma =ρ ma (Vs ma +Δ) 2

[0108] Where K dry is the bulk modulus of dry rock, μ dry is the dry rock shear modulus, K ma is the bulk modulus of rock matrix after stress and fracture constraints, μ ma is the shear modulus of the rock matrix after stress and fracture constraint, A is the pore flatness of sandstone, and B is the pore flatness of mudstone.

[0109] Embodiment 3:

[0110] like Figure 1 As shown, the present invention provides an anisotropic rock physics modeling method, comprising the following steps:

[0111] Step S1: Obtain the attributes of the target layer segment;

[0112] Step S2: using the properties of the target layer to establish a matrix model;

[0113] Step S3: using imaging logging data, calculating the angle between the crack strike and the maximum principal stress direction;

[0114] Step S4: using dipole acoustic wave data, by evaluating the influence of different angles on shear wave velocity, an anisotropic influence factor model is established;

[0115] Step S5: using the matrix model and the anisotropic influencing factor model to establish a dry rock model;

[0116] Step S6: establishing an elastic model of pore fluid;

[0117] Step S7: Based on the dry rock model and the elastic model of the pore fluid, an anisotropic saturated rock model is established.

[0118] The difference between this embodiment and the second embodiment is that:

[0119] In step S6, an elastic model of the pore fluid under different temperature and pressure environments is established, and the bulk modulus and fluid density of the equivalent pore fluid are calculated using the Wodd equation according to the saturation information:

[0120]

[0121] ρ f =S w ρ w +(1-S w )ρ h

[0122] Where K f is the bulk modulus of the fluid, ρ f is the fluid density, S w is water saturation, K w is the bulk modulus of formation water, K h is the bulk modulus of hydrocarbons, ρ w is the formation water density, ρ h is the density of hydrocarbons.

[0123] The step S7 establishes the elastic modulus of anisotropic saturated rock based on the dry rock model and the elastic model of pore fluid:

[0124]

[0125] μ sat =μ dry

[0126] ρ sat =φρ f+(1-φ)ρ ma

[0127] Where K sat is the bulk modulus of saturated rock, μ sat is the shear modulus of saturated rock, ρ sat is the saturated rock density;

[0128] Apply the relationship between elastic modulus and velocity formula to convert elastic modulus to velocity:

[0129]

[0130]

[0131] Where Vp is the rock longitudinal wave velocity, and Vs is the rock shear wave velocity.

[0132] The present invention provides an anisotropic rock physics modeling method, which introduces an influencing factor to correct the anisotropic saturated rock model, thereby eliminating the influence of the differences in stress directions and fracture occurrences in different layers at different well points on the shear wave velocity. The shear wave velocity is obtained by using the anisotropic saturated rock model, and the distribution law of elastic parameters is obtained by using the shear wave velocity. The distribution law of reservoir elastic parameters under formation anisotropy can be truly reflected, and basic data support can be provided for subsequent reservoir inversion, rock brittleness evaluation, etc.

[0133] The present invention takes into account the propagation modes of longitudinal and transverse waves. Longitudinal waves are mainly compression waves, and high and low angle cracks have basically the same effects on longitudinal waves. Transverse waves are polarized waves, and high angle cracks (angle greater than 60 degrees) have a greater impact on transverse waves. It is also necessary to further combine the crack direction to determine the impact of crack density on transverse waves.

[0134] In a strong stress environment, the shear wave velocity is affected not only by the crack direction but also by the maximum stress. When the maximum principal stress direction is basically consistent with the crack direction, the crack has little effect on the shear wave velocity. When the angle between the maximum principal stress direction and the crack direction exceeds the threshold Q, the crack has a great effect on the shear wave velocity. When the angle between the maximum principal stress direction and the crack direction is less than the threshold Q, the crack has a small effect on the shear wave velocity. The threshold Q is determined by making a relationship diagram between the angle and the shear wave velocity.

[0135] Combined with imaging logging, the angle between the fracture trend of the target layer and the direction of the maximum principal stress is analyzed. According to the different ranges of the angle, different influencing factors are applied to different fractures to constrain the elastic modulus of dry rock.

[0136] from Figure 5 and Figure 6The analysis shows that when the angle is less than 30 degrees, the crack density has a small effect on the shear wave velocity, and when the angle is greater than 30 degrees, the crack has a large effect on the shear wave velocity. The threshold Q is 30 degrees. Based on this, the influence factors of crack density when the angle is less than 30 degrees and the influence factors of crack density when the angle is greater than 30 degrees are established. The influence factors are obtained by fitting the shear wave velocity and crack density of the dipole acoustic wave data, and then the difference in the influence of crack density on the shear wave velocity at different angle ranges is obtained.

[0137] When applying the Kustor-Toksoz formula to obtain the elastic modulus of dry rock, the difference in the effect of fracture density on shear wave velocity at different angles is introduced to correct the elastic modulus of dry rock in the layer with large-angle fractures. Then, the shear wave velocity of rock is obtained, and elastic parameter plates are made to analyze lithology or fluid.

[0138] Figure 7 This is the cross plot of the P-wave velocity ratio and P-wave impedance calculated from dipole acoustic wave data. Generally, sandstone and mudstone in reservoirs have distinct characteristics, that is, the P-wave velocity ratio of sandstone is low, while that of mudstone is high. However, since the shear wave velocity is affected by the occurrence of fractures and the direction of stress, the measured data show that the P-wave velocity ratio of most sandstones is equivalent to that of mudstone, which is obviously inconsistent with the true distribution law of elastic parameters.

[0139] like Figure 8 As shown in the figure, after the application of this model, the P-wave and S-wave velocity ratios conform to the laws of rock physics, can effectively divide reservoir lithology, and are suitable for subsequent reservoir inversion.

[0140] The anisotropic rock physics modeling method of the present invention is mainly a fine rock physics modeling technology for the case where the elastic parameters measured in a strong stress environment and a fractured reservoir are disordered and cannot guide the subsequent reservoir inversion, and can provide a prediction mechanism for the subsequent reservoir inversion. The present invention considers the restoration of the true elastic parameters of the reservoir when the fractures with high inclination angles (inclination angle greater than 60 degrees) are subject to dual constraints under different fracture directions and principal stress directions. In the application process, it is necessary to consider the angle between the fracture direction and the maximum principal stress, combine imaging logging and dipole acoustic wave data, establish two different influencing factors and apply them to the modeling, thereby eliminating the influence of the fracture occurrence and stress direction differences on the elastic parameters, and can effectively identify the lithology and fluid of the reservoirs with strong stress environments and fracture development.

[0141] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A method for anisotropic rock physics modeling, It is characterized in that The following steps are involved: Step S1: Obtain the attributes of the target layer segment; Step S2: using the properties of the target layer to establish a matrix model; Step S3: using imaging logging data, calculating the angle between the crack strike and the maximum principal stress direction; Step S4: using dipole acoustic wave data, by evaluating the influence of different angles on shear wave velocity, an anisotropic influence factor model is established; Step S5: using the matrix model and the anisotropic influencing factor model to establish a dry rock model; Step S6: establishing an elastic model of pore fluid; Step S7: Based on the dry rock model and the elastic model of the pore fluid, an anisotropic saturated rock model is established.

2. The anisotropic rock physics modeling method according to claim 1, It is characterized in that The step S1 includes the following steps: Step H1: pre-processing the logging data; Step H2: Use logging data to interpret the properties of the target layer.

3. The anisotropic rock physics modeling method according to claim 2, It is characterized in that In the step H1, the preprocessing includes well curve environment correction and well curve standardization.

4. The anisotropic rock physics modeling method according to claim 2, It is characterized in that In step H2, the properties of the target layer segment include shale content, porosity, saturation and fracture density.

5. The anisotropic rock physics modeling method according to claim 1, It is characterized in that In step S2, the Wyllie time-averaged equation is applied to establish the rock matrix elastic modulus and matrix density: Among them, Vp ma is the longitudinal wave velocity of rock foundation, Vs ma is the rock matrix shear wave velocity, φ is the porosity, V clay is the clay content, Vp quartz is the quartz longitudinal wave velocity, Vs quartz is the quartz shear wave velocity, Vp clay is the clay longitudinal wave velocity, Vs clay is the clay shear wave velocity, ρ ma is the matrix density, ρ quartz is the density of quartz, ρ clay is the density of clay.

6. The anisotropic rock physics modeling method according to claim 1, It is characterized in that In step S3, the imaging logging data is used to identify the induced fractures and the structural fractures respectively, the maximum principal stress direction is determined by the induced fractures, the distribution of the inclination angle and the strike of the structural fractures is statistically analyzed, and a relationship diagram between the inclination angle and the longitudinal wave and the shear wave is prepared to calculate the angle between the strike of the fracture and the maximum principal stress direction.

7. The anisotropic rock physics modeling method according to claim 1, It is characterized in that In step S4, the influence factor of crack density on angle is established by using dipole acoustic wave data. By evaluating the influence of different angles on shear wave velocity, the threshold value Q of the angle is analyzed and obtained. The calculation formula of the anisotropic influence factor model is as follows: D=D 2 -D 1 Among them, Δ 1 is the variation of shear wave velocity with crack density when the angle is less than Q, Δ 2 is the change of shear wave velocity with crack density when the angle is greater than Q; Δ is the difference in the influence of the shear wave velocity when the angle is greater than Q and when the angle is less than Q; FDI is the crack density; α is the influence factor of crack density on the angle when the angle is less than Q, and β is the influence factor of crack density on the angle when the angle is greater than Q.

8. The anisotropic rock physics modeling method according to claim 7, It is characterized in that The influence factor of the crack density on the angle is obtained by fitting the shear wave velocity and crack density of the dipole acoustic wave data.

9. The anisotropic rock physics modeling method according to claim 8, It is characterized in that In step S5, the matrix model and the anisotropic influencing factor model are used to establish the elastic modulus of dry rock under the constraints of the maximum principal stress direction and the crack orientation.

10. The anisotropic rock physics modeling method according to claim 9, It is characterized in that Using the Kustor-Toksoz formula, the elastic modulus of dry rock is calculated as: in, μ ma =ρ ma (Vs ma +Δ) 2 Where K dry is the bulk modulus of dry rock, μ dry is the dry rock shear modulus, K ma is the bulk modulus of rock matrix after stress and fracture constraint, μ ma is the shear modulus of the rock matrix after stress and fracture constraint, A is the pore flatness of sandstone, and B is the pore flatness of mudstone.

11. The anisotropic rock physics modeling method according to claim 10, It is characterized in that In step S6, an elastic model of pore fluid under different temperature and pressure environments is established.

12. The anisotropic rock physics modeling method according to claim 11, It is characterized in that In step S6, the bulk modulus and fluid density of the equivalent pore fluid are calculated using the Wodd equation according to the saturation information: r f =S w r w +(1-S w )r h Where K f is the bulk modulus of the fluid, ρ f is the fluid density, S w is water saturation, K w is the bulk modulus of formation water, K h is the bulk modulus of hydrocarbons, ρ w is the formation water density, ρ h is the density of hydrocarbons.

13. The anisotropic rock physics modeling method according to claim 12, It is characterized in that In step S7, the elastic modulus of anisotropic saturated rock is established based on the dry rock model and the elastic model of pore fluid: m sat =μ dry r sat =fr f +(1-φ)ρ ma Where K sat is the bulk modulus of saturated rock, μ sat is the shear modulus of saturated rock, ρ sat is the saturated rock density.

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