Computational method and system for dispersion and attenuation of longitudinal waves in partially saturated porous fractured media

Abstract

The present disclosure provides a method and system for calculating the dispersion and attenuation of longitudinal waves in a partially saturated porous fracture medium, comprising: acquiring pore structure parameters in a sample image; constructing a partially saturated porous fracture medium according to the pore structure parameters; constructing a dissipation equation, a potential energy equation and a kinetic energy equation of the partially saturated porous fracture medium according to the partially saturated porous fracture medium and component parameters; constructing a group of wave propagation dynamic equations of the partially saturated porous fracture medium according to the dissipation equation, the potential energy equation and the kinetic energy equation; and calculating the dispersion and attenuation of longitudinal waves according to the group of wave propagation dynamic equations.

Description

Technical Field

[0001] The present disclosure relates to the technical field of seismic rock physics, and in particular to a method and system for calculating longitudinal wave dispersion and attenuation in a partially saturated porous fracture medium. Background Art

[0002] Deepwater deep reservoirs have experienced complex geological processes, resulting in significant multi-scale characteristics of their pore structure and fluid distribution. This multi-scale nature is reflected at the micro, meso and seismic scales, and factors such as pore type, fracture, and fluid distribution at each scale have different degrees of influence on the response of P-waves. At the microscale, different types of pores in the reservoir (such as intergranular pores, dissolution pores, microcracks, and intercrystalline pores of clay minerals) have significant differences in their responses to P-waves. The existence and distribution of these pores will change the physical parameters of the rock, such as density and elastic modulus, thereby affecting the propagation speed and attenuation characteristics of P-waves. At the mesoscale, factors such as fractures, clay fillings, and fluid patches become the main factors controlling the wave response characteristics. The presence of fractures will lead to the scattering and diffraction of P-waves, while clay fillings and fluid patches will affect the elastic and inelastic properties of rocks, further affecting the propagation characteristics of P-waves. At the seismic scale, the fractures, bedding planes, and fluid distribution characteristics of the reservoir have an important influence on the propagation and reflection of seismic waves. These factors can cause velocity dispersion and attenuation of seismic waves, making seismic interpretation more complicated.

[0003] In order to predict the properties of underground medium reservoirs, laboratory measurement data, well logging curves or rock physics models are usually used to establish quantitative relationships between rock elastic parameters and seismic attributes. However, conventional ultrasonic experimental observations alone cannot verify the applicability of rock physics models in the low-frequency band, because there are significant differences in the propagation characteristics of seismic waves in the low-frequency band and ultrasonic waves in the high-frequency band.

[0004] Therefore, a key challenge is how to establish the connection between multi-scale rock physical characteristics, which requires studying the effects of heterogeneity on the elastic and inelastic properties of rocks at different spatial scales and frequencies. Summary of the invention

[0005] The present disclosure provides a method and system for calculating the dispersion and attenuation of longitudinal waves in a partially saturated porous fracture medium, so as to at least solve the above technical problems existing in the prior art.

[0006] According to a first aspect of the present disclosure, a method for calculating longitudinal wave dispersion and attenuation in a partially saturated porous fracture medium is provided, the method comprising:

[0007] Obtaining pore structure parameters in sample images;

[0008] According to the pore structure parameters, construct a partially saturated pore fracture medium;

[0009] According to the partially saturated porous fractured medium and component parameters, a dissipation equation, a potential energy equation and a kinetic energy equation of the partially saturated porous fractured medium are constructed;

[0010] According to the dissipation equation, potential energy equation and kinetic energy equation, a group of wave propagation dynamic equations of the partially saturated porous fracture medium is constructed;

[0011] The longitudinal wave dispersion and attenuation are calculated based on the wave propagation dynamics equations.

[0012] In one possible implementation manner, the step of obtaining pore structure parameters in the sample image includes:

[0013] Acquiring a pore structure in the sample image;

[0014] The pore structure is analyzed by using an image segmentation method to obtain pore distribution characteristics and a probability density distribution histogram;

[0015] According to the pore distribution characteristics, the probability density distribution histogram is fitted using a distribution function to obtain pore structure parameters.

[0016] In one embodiment, constructing a partially saturated porous fractured medium includes:

[0017] The preset pore fracture medium model includes the following components: a main skeleton, a first fluid, a second fluid, an embedded body containing fractures, and fluid patches; the main skeleton is partially saturated with the first fluid and the second fluid; the embedded body is saturated with the first fluid;

[0018] The radius parameters characterizing the cracks and fluid patches in the pore structure parameters are discretized into a plurality of components of different sizes, and the cracks and fluid patches of each group are sequentially added into the main skeleton in the order of the radius parameters from large to small;

[0019] Whenever the porosity of the main skeleton meets the preset conditions, the preset pore fracture medium model is used as a partially saturated pore fracture medium.

[0020] In one embodiment, the dissipation equation of the partially saturated porous fracture medium is established, including:

[0021] The dissipation equation is established according to the component parameters of the partially saturated porous fracture medium, the Biot dissipation parameters of the fluid in the main skeleton and the embedded body, the waveguide flow dissipation parameters of the first fluid at the interface between the main skeleton and the embedded body, and the waveguide flow dissipation parameters of the first fluid and the second fluid at the interface between the main skeleton.

[0022] In one embodiment, the potential energy equation of the partially saturated porous fracture medium is established, including:

[0023] According to the displacement divergence field of the fluid in the main skeleton and the embedded body, the strain energy generated at the interface between the solid, liquid and immiscible fluid in the partially saturated porous fracture medium is calculated to obtain a first potential energy equation;

[0024] The first potential energy equation is coupled with the second potential energy equation to obtain the potential energy equation; the second potential energy equation characterizes the elastic strain energy in the partially saturated porous fracture medium.

[0025] In one embodiment, the kinetic energy equation of the partially saturated porous fracture medium is established, including:

[0026] The kinetic energy equation of the partially saturated porous fractured medium is established based on the kinetic energy caused by the global flow in the partially saturated porous fractured medium, the kinetic energy caused by the local flow at the interface between the main skeleton saturated with the first fluid and the embedded body, and the kinetic energy caused by the local flow at the interface between the first fluid and the second fluid at the main skeleton.

[0027] In one embodiment, according to the dissipation equation, the potential energy equation and the kinetic energy equation, a group of wave propagation dynamic equations of the partially saturated porous fracture medium is constructed, including:

[0028] After each set of component fractures and fluid patches is added to the main skeleton, a dissipation equation, a potential energy equation and a kinetic energy equation of the current partially saturated porous fracture medium are obtained;

[0029] Substituting the dissipation equation, potential energy equation and kinetic energy equation into the Lagrangian formula to obtain the wave propagation dynamics equation group of the current round, and obtaining the elastic modulus of the main skeleton in the next adding operation;

[0030] The above operation is repeated until all the cracks and fluid patches are added into the main skeleton, and the wave propagation dynamic equations of the partially saturated porous fracture medium are obtained.

[0031] In one embodiment, the step of obtaining the elastic modulus of the main skeleton in the next adding operation includes:

[0032] Based on the plane wave analysis method, the bulk modulus and shear modulus of the saturated immiscible fluid composite medium in the partially saturated porous fracture medium are determined using the wave propagation dynamics equations of the current round;

[0033] Based on Gassmann theory, the elastic modulus of dry rock of the composite medium in the partially saturated porous fracture medium is determined, and the elastic modulus of dry rock of the composite medium is used as the elastic modulus of the main skeleton in the next adding operation.

[0034] In one embodiment, the longitudinal wave dispersion and attenuation are calculated according to the wave propagation dynamics equations, including:

[0035] Obtaining the wave number of the longitudinal wave according to the wave propagation dynamics equation group;

[0036] The longitudinal wave dispersion and attenuation are calculated based on the wave number of the longitudinal wave.

[0037] According to a second aspect of the present disclosure, a system for calculating longitudinal wave dispersion and attenuation in a partially saturated porous fracture medium is provided, the system comprising:

[0038] An acquisition module, used for acquiring pore structure parameters in a sample image;

[0039] A construction module, used for constructing a partially saturated pore fracture medium according to the pore structure parameters;

[0040] The construction module is further used to construct a dissipation equation, a potential energy equation and a kinetic energy equation of the partially saturated porous fracture medium according to the partially saturated porous fracture medium and component parameters;

[0041] The construction module is also used to construct the wave propagation dynamics equation group of the partially saturated porous fracture medium according to the dissipation equation, the potential energy equation and the kinetic energy equation;

[0042] A calculation module is used to calculate the longitudinal wave dispersion and attenuation according to the wave propagation dynamics equations.

[0043] According to a third aspect of the present disclosure, there is provided an electronic device, including:

[0044] at least one processor; and

[0045] a memory communicatively connected to the at least one processor; wherein,

[0046] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method described in the present disclosure.

[0047] According to a fourth aspect of the present disclosure, a non-transitory computer-readable storage medium storing computer instructions is provided, wherein the computer instructions are used to cause the computer to execute the method described in the present disclosure.

[0048] The present invention discloses a method and system for calculating the dispersion and attenuation of longitudinal waves in partially saturated porous fractured media. By analyzing the reservoir rock sample image, multi-scale pore structure parameters are obtained, and a rock physics model capable of describing the partially saturated porous media is constructed. A dissipation equation, a potential energy equation, and a kinetic energy equation are established to describe the wave propagation characteristics in the partially saturated porous fractured media, and a group of wave propagation dynamic equations are established based on the above equations. The velocity dispersion and attenuation characteristics of the longitudinal waves in the reservoir are calculated by using the constructed group of wave propagation dynamic equations in combination with specific pore structure parameters and fluid distribution characteristics. By constructing a multi-scale rock physics model, the method realizes the association between the pore structure and fluid distribution characteristics from the microscopic to the seismic scale and the longitudinal wave response, which helps to more comprehensively understand the propagation characteristics of waves in complex reservoirs. Moreover, compared with traditional ultrasonic experimental observations, this method can predict the propagation characteristics of low-frequency seismic waves, make up for the shortcomings of high-frequency ultrasonic experiments in the verification of applicability in the low-frequency band, and improve the accuracy of seismic interpretation.

[0049] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, in which:

[0051] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0052] Figure 1 A schematic diagram of the implementation process of the method for calculating the dispersion and attenuation of longitudinal waves in a partially saturated porous fracture medium according to an embodiment of the present disclosure is shown;

[0053] Figure 2 A schematic diagram of the implementation process of obtaining pore structure parameters in a sample image according to an embodiment of the present disclosure is shown;

[0054] Figure 3 A schematic diagram of the implementation process of constructing a partially saturated porous fracture medium according to an embodiment of the present disclosure is shown;

[0055] Figure 4 A schematic diagram of the implementation process of establishing a potential energy equation for a partially saturated porous fracture medium according to an embodiment of the present disclosure is shown;

[0056] Figure 5 A schematic diagram of the implementation process of constructing a group of wave propagation dynamic equations for a partially saturated porous fracture medium according to an embodiment of the present disclosure is shown;

[0057] Figure 6 A schematic diagram of the implementation process of obtaining the elastic modulus of the main skeleton in the next adding operation according to an embodiment of the present disclosure is shown;

[0058] Figure 7 A schematic diagram of the implementation process of calculating longitudinal wave dispersion and attenuation in an embodiment of the present disclosure is shown;

[0059] FIG8 is a schematic diagram showing the variation of longitudinal wave velocity and attenuation with frequency under different conditions of an embodiment of the present disclosure;

[0060] in, Figure 8a A schematic diagram showing the variation of the longitudinal wave velocity and attenuation with frequency in different radius ranges at 90% water saturation in the embodiment of the present disclosure;

[0061] Figure 8b A schematic diagram showing the change of rock longitudinal wave velocity and attenuation with frequency at different saturations in an embodiment of the present disclosure is shown;

[0062] Figure 8c A schematic diagram showing the variation of the P-wave velocity and attenuation with water saturation in a rock partially saturated with gas and water at different frequencies according to an embodiment of the present disclosure;

[0063] Fig. 9 A schematic diagram of the structure of a calculation system for longitudinal wave dispersion and attenuation in a partially saturated porous fracture medium according to an embodiment of the present disclosure is shown;

[0064] Fig.10 A schematic diagram of the structure of an electronic device according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0065] In order to make the purpose, features, and advantages of the present disclosure more obvious and easy to understand, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0066] The present disclosure provides a method for calculating the dispersion and attenuation of longitudinal waves in a partially saturated porous fracture medium. Figure 1 As shown, the method includes:

[0067] Step 101: Acquire pore structure parameters in a sample image.

[0068] In natural porous media or deep-water reservoirs, pore structures of various scales (such as cracks, fluid patches, etc.) are usually observed, and these pore structures are usually heterogeneous. A large number of studies have shown that the pore structure of reservoir rocks has significant multi-scale distribution characteristics. Therefore, by obtaining sample images of reservoir rocks and analyzing the pore structures in the sample images, the pore structure parameters can be obtained.

[0069] Step 102: construct a partially saturated pore fracture medium according to the pore structure parameters.

[0070] In this example, based on the pore structure parameters obtained in the previous step, a rock physics model is constructed to characterize partially saturated porous fractured media. The model of partially saturated porous fractured media can reflect complex partially saturated porous media, establish the relationship between fracture properties, fluid saturation, fractal dimension, etc. and P-wave velocity dispersion and attenuation, and analyze the broadband P-wave response characteristics of reservoir rocks by combining pore structure feature analysis and multi-scale observation data.

[0071] Step 103: constructing a dissipation equation, a potential energy equation and a kinetic energy equation of the partially saturated porous fractured medium according to the partially saturated porous fractured medium and component parameters.

[0072] This paper establishes the connection between multi-scale rock physical characteristics from the following three perspectives and studies the impact of heterogeneity on the elastic and inelastic properties of rocks at different spatial scales and frequencies:

[0073] In this example, when the wave propagates in the medium, a relative displacement occurs between the fluid and the solid skeleton, which causes energy dissipation. Therefore, the dissipation equation for partially saturated porous fracture media is established by considering the Biot dissipation and waveguide dissipation mechanisms.

[0074] The relaxation effect mainly refers to the energy dissipation and velocity dispersion phenomenon generated in the process of wave propagation in porous media due to the interaction between different phases (such as solid skeleton, pore fluid, etc.). Therefore, based on the Biot theory, the relaxation effect caused by waveguide flow at the interface of different phases is coupled to the potential energy equation, and the potential energy equation of partially saturated porous fracture media is established.

[0075] In addition, the analytical relationship between the radius of the spherical embedded body and the fluid increment in the waveguide flow process must be considered. Therefore, the kinetic energy equation of partially saturated porous fracture media is established.

[0076] Step 104: construct a group of wave propagation dynamic equations of the partially saturated porous fracture medium according to the dissipation equation, the potential energy equation and the kinetic energy equation.

[0077] In this example, the dissipation equation, potential energy equation and kinetic energy equation obtained in the above steps are used to derive the wave propagation dynamics equations of partially saturated porous fracture media based on Hamiltonian principle and differential equivalent medium theory. The specific derivation process will be described in detail in the subsequent embodiments.

[0078] Step 105: Calculate the longitudinal wave dispersion and attenuation according to the wave propagation dynamics equations.

[0079] In this example, the P-wave velocity dispersion and attenuation in the reservoir rock are calculated based on the derived set of dynamic equations for wave propagation, specific values ​​of pore structure parameters in a partially saturated porous fractured medium, and fluid distribution characteristics.

[0080] The present disclosure proposes a method for calculating the dispersion and attenuation of longitudinal waves in partially saturated porous fracture media. By analyzing the reservoir rock sample image, multi-scale pore structure parameters are obtained, and a rock physics model capable of describing partially saturated porous media is constructed. A dissipation equation, a potential energy equation, and a kinetic energy equation describing the wave propagation characteristics in partially saturated porous fracture media are established, and a group of wave propagation dynamic equations are established based on the above equations. The velocity dispersion and attenuation characteristics of longitudinal waves in the reservoir are calculated by using the constructed group of wave propagation dynamic equations, combined with specific pore structure parameters and fluid distribution characteristics. By constructing a multi-scale rock physics model, this method realizes the association between the pore structure and fluid distribution characteristics from the microscopic to the seismic scale and the longitudinal wave response, which helps to more comprehensively understand the propagation characteristics of waves in complex reservoirs. Moreover, compared with traditional ultrasonic experimental observations, this method can predict the propagation characteristics of low-frequency seismic waves, making up for the shortcomings of high-frequency ultrasonic experiments in verifying the applicability of low-frequency bands, and improving the accuracy of seismic interpretation.

[0081] In one example, the process of obtaining the pore structure parameters in the sample image is as follows: Figure 2 As shown, including:

[0082] Step 201: Acquire the pore structure in the sample image.

[0083] In this example, sample images of the reservoir are obtained by casting thin sections, scanning electron microscopy and other techniques for subsequent analysis of the pore structure in the sample images, including: embedded bodies containing fractures and fluid patches.

[0084] An embedded body usually refers to a rock or mineral body that is embedded in another rock or matrix of different properties, forming a clear boundary or interface. A fissure-containing embedded body refers to a structural feature in which fissures or cracks exist inside or at the edge of the embedded body. Fluid patches usually refer to the local area of ​​the rock occupied by fluids (such as water, oil, gas, etc.), and the fluid may completely or partially fill the pores or cracks of the rock. The presence of cracks and fluid patches will affect the mechanical properties of the reservoir rock and the fluid migration characteristics, thereby affecting the dispersion and attenuation of the P-wave velocity.

[0085] Step 202: Analyze the pore structure using an image segmentation method to obtain pore distribution characteristics and a probability density distribution histogram.

[0086] In this example, a large number of studies have shown that the pore structure of reservoir rocks has significant multi-scale distribution characteristics, such as fractal distribution, exponential distribution or Gaussian distribution. The image segmentation method is used to analyze the scanned pore structure to obtain the size distribution range and probability density distribution histogram of the pore structure.

[0087] Step 203: According to the pore distribution characteristics, a distribution function is used to fit the probability density distribution histogram to obtain pore structure parameters.

[0088] In this example, when the pore structure radius is exponentially distributed, its volume fraction can be expressed as ,in is a constant, is the pore structure radius. As the radius increases, the volume fraction decreases exponentially. When the pore structure radius is Gaussian distributed, its volume fraction can be expressed as ,in and are the mean and variance of the pore structure radius; when the pore structure radius is fractal distributed, its volume fraction can be expressed as ,in and are the minimum and maximum radii of the pore structure, is the Euclidean dimension, is the fractal dimension.

[0089] After obtaining the size distribution range and probability density distribution histogram of the pore structure, the probability density distribution histogram is fitted using an exponential, Gaussian or fractal function according to the pore distribution characteristics to obtain the pore structure parameters.

[0090] In one example, the process of constructing a partially saturated porous fracture medium according to the pore structure parameters includes:

[0091] The preset pore fracture medium model includes the following components: a main skeleton, a first fluid, a second fluid, an embedded body containing fractures, and fluid patches; the main skeleton is partially saturated with the first fluid and the second fluid; the embedded body is saturated with the first fluid. The radius parameters characterizing the fractures and fluid patches in the pore structure parameters are discretized into a plurality of components of different sizes, and the fractures and fluid patches of each component are sequentially added to the main skeleton in the order of the radius parameters from large to small; whenever the porosity of the main skeleton meets the preset conditions, the preset pore fracture medium model is used as a partially saturated pore fracture medium.

[0092] like Figure 3 As shown in the figure, the partially saturated porous fracture medium is partially saturated with two immiscible fluids, and the matrix containing hard pores is used as the main skeleton, which contains a series of embedded bodies with soft pores (such as microcracks, fractures, etc.) of different sizes. Due to the influence of capillary force and wettability of filling materials, microcracks or particle contacts in rocks are usually saturated first, so the main skeleton can be considered partially saturated, while the embedded bodies are only saturated with one fluid.

[0093] Assume that the total porosity of the partially saturated porous fracture medium is The porosity of the main framework and the embedded body are and According to the scale distribution characteristics and differential equivalent medium theory, the fractures and fluid patches to be added in the partially saturated porous fracture medium are discretized into j components with different radii, that is, the fracture and fluid patch radii are discretized into and , and then each group of cracks and fluid patches are added to the main skeleton in order from large to small radius.

[0094] It should be noted that each time a crack and a fluid patch are added, the radius of the crack and the fluid patch follows the following relationship: and At the mth addition, a set of volume fractions is The cracks are embedded into the main skeleton. At this time, the absolute porosity of the main skeleton partially saturated with the first fluid is , the absolute porosity of the main skeleton partially saturated with the second fluid is ; The absolute porosity of the embedding saturated with the first fluid is .in, and are the saturations of the first and second fluids in the main skeleton, respectively, and .

[0095] When adding a radius of The crack and radius are After the fluid patch, if its increased porosity meets the preset conditions and When , this medium is regarded as a partially saturated porous fracture medium. is the sum of the volume fractions of all cracks with different radii; is the absolute porosity of all the main skeletons saturated with the second fluid sum.

[0096] In addition, the densities of the first fluid and the second fluid are and The viscosities are and , and the bulk moduli are and .

[0097] In one example, the dissipation equation of the partially saturated porous fracture medium is established, including:

[0098] The dissipation equation is established based on the component parameters of the partially saturated porous fracture medium, the Biot dissipation parameters of the fluid in the main skeleton and the embedded body, the waveguide flow dissipation parameters at the interface between the main skeleton saturated with the first fluid and the embedded body, and the waveguide flow dissipation parameters at the interface between the first fluid and the second fluid in the main skeleton.

[0099] In this example, based on Biot dissipation and two types of waveguide flow dissipation mechanisms, the dissipation equation for partially saturated porous fracture media is established as follows:

[0100] (1)

[0101] in, represents the Biot dissipation coefficient (n=1, 2, 3); is the average particle translation of the main skeleton; is the displacement of the main phase fluid in the main skeleton, is the displacement of the fluid in the embedded body and is the displacement of the fluid within the fluid patch in the main skeleton; is the viscosity of the first fluid, To represent the fluid strain increment of the first fluid at the interface between the main skeleton and the embedded body, The radius of each crack added to the main skeleton; is the main skeleton permeability; The radius of each fluid patch added to the main skeleton; Represents the fluid strain increment at the interface between the first fluid and the second fluid on the main skeleton.

[0102] In one example, the potential energy equation of the partially saturated porous fracture medium is established, such as Figure 4 As shown, including:

[0103] Step 401: Calculate the strain energy generated at the interface between solid, liquid and immiscible fluid in the partially saturated porous fracture medium according to the displacement divergence field of the fluid in the main skeleton and the embedded body to obtain a first potential energy equation; Step 402: Couple the first potential energy equation with the second potential energy equation to obtain the potential energy equation; the second potential energy equation characterizes the elastic strain energy in the partially saturated porous fracture medium.

[0104] Specifically, based on the Biot theory, the relaxation effect caused by the waveguide flow at different phase interfaces is coupled to the potential energy equation, and the strain energy is obtained as follows:

[0105] (2)

[0106] in, , , , , , , and They represent elastic parameters, and and the second strain invariant, respectively, is the displacement divergence field of the main phase fluid in the main skeleton, is the displacement divergence field of the fluid in the embedded body, The displacement divergence field of the fluid in the fluid patch of the main skeleton.

[0107] In one example, the elastic parameter in the above formula (2) is , , , , , , and , can be obtained through the following equation:

[0108] (3)

[0109] in, and are the bulk moduli of the first and second fluids, respectively, is the particle bulk modulus, and are the bulk modulus and shear modulus of the dielectric skeleton, respectively.

[0110] The ratio of the expansion volume of the first fluid in the main skeleton to the expansion volume in the embedded body can be obtained by the following equation:

[0111] (4)

[0112] in, and are the bulk moduli of the main skeleton and embedded body, respectively.

[0113] In one example, the kinetic energy equation of the partially saturated porous fracture medium is established, including:

[0114] The kinetic energy equation of the partially saturated porous fractured medium is established based on the kinetic energy caused by the global flow in the partially saturated porous fractured medium, the kinetic energy caused by the local flow at the interface between the main skeleton saturated with the first fluid and the embedded body, and the kinetic energy caused by the local flow at the interface between the first fluid and the second fluid at the main skeleton.

[0115] (5)

[0116] in, and (i=1, 2 and 3) are the solid and fluid displacement components respectively, is a spatial variable, 1, 2, 3 correspond to the spatial directions x, y, z respectively; , , , , , and The density coefficient of the double-porosity medium is derived based on the density parameter relationship of the single-porosity medium given by Biot (1956).

[0117] Among them, the density coefficient , , , , , and It can be derived by the following formula:

[0118] (6)

[0119] in, is the particle density, and The tortuosity of the pores of the main skeleton and embedded bodies.

[0120] In one example, the wave propagation dynamics equations of the partially saturated porous fracture medium are constructed according to the dissipation equation, the potential energy equation and the kinetic energy equation, such as: Figure 5 As shown, including:

[0121] Step 501: After each set of component fractures and fluid patches is added to the main skeleton, the dissipation equation, potential energy equation and kinetic energy equation of the current partially saturated porous fracture medium are obtained.

[0122] In this example, each time a set of component fractures and fluid patches is added to the main skeleton, the dissipation equation, potential energy equation and kinetic energy equation of the current partially saturated porous fracture medium can be obtained through the above steps if the porosity preset conditions of the main skeleton are met.

[0123] Step 502: Substitute the dissipation equation, potential energy equation and kinetic energy equation into the Lagrangian formula to obtain the wave propagation dynamics equation group of the current round, and obtain the elastic modulus of the main skeleton in the next adding operation.

[0124] Based on Hamilton's principle, the Lagrangian function can be written as Substituting the potential energy equation, kinetic energy equation and dissipation function into the Lagrangian equation, the wave propagation dynamics equations of the current partially saturated porous fracture medium can be expressed as:

[0125] (7a)

[0126] (7b)

[0127] (7c)

[0128] (7d)

[0129] (7e)

[0130] (7f)

[0131] in, , , and are the corresponding four displacement divergence fields. Formulas (7a)-(7d) represent the elastic wave propagation dynamic equations in the solid phase and different fluid phase regions, respectively. Formulas (7e)-(7f) represent two types of local flow dynamics control equations, respectively.

[0132] Furthermore, the elastic modulus of the main skeleton in the next adding operation is obtained based on the above formulas (7a)-(7f), and the specific obtaining process will be described in detail in the subsequent embodiments.

[0133] Step 503: Repeat the above operations until all the fractures and fluid patches are added into the main skeleton, and obtain the wave propagation dynamic equations of the partially saturated pore fracture medium.

[0134] In this example, the above steps are repeated until all fractures and fluid patches are added to the main skeleton to obtain the corresponding wave propagation dynamic equations for partially saturated porous fracture media:

[0135] (8a)

[0136] (8b)

[0137] (8c)

[0138] (8d)

[0139] (8e)

[0140] (8f)

[0141] Among them, the elastic coefficient , , , , , , and , density coefficient , , , , , and It can be obtained from the discretization process of the above formulas (1)-(8).

[0142] In one example, obtaining the elastic modulus of the main skeleton in the next adding operation includes:

[0143] Step 601: Based on a plane wave analysis method, the bulk modulus and shear modulus of the saturated immiscible fluid composite medium in the partially saturated porous fracture medium are determined using the wave propagation dynamics equations of the current round.

[0144] In this example, the plane wave analysis method is used to study the propagation characteristics of waves in the medium. The bulk modulus and shear modulus of the saturated immiscible fluid composite medium in the partially saturated porous fracture medium can be solved through the wave propagation dynamics equations that have been constructed in the current round. These two moduli are key parameters that describe the resistance of partially saturated porous fracture media to compression and shear deformation.

[0145] Step 602: Based on Gassmann theory, determine the elastic modulus of dry rock of the composite medium in the partially saturated porous fracture medium, and use the elastic modulus of dry rock of the composite medium as the elastic modulus of the main skeleton in the next adding operation.

[0146] In this example, after obtaining the bulk modulus and shear modulus of the current saturated immiscible fluid composite medium, it is necessary to further determine the elastic modulus of the composite medium in a completely dry (i.e., fluid-free) state, which is usually called the dry rock elastic modulus. Gassmann theory is a theory used to estimate the elastic modulus of porous media (such as rocks) in dry and saturated states.

[0147] Specifically, the elastic modulus of the dry rock of the composite medium is estimated by using the Gassmann theory, combined with the previously calculated bulk modulus and shear modulus. This elastic modulus will be used as the elastic modulus of the main skeleton when the fractures and fluid patches are added next time, because the elastic properties of the main skeleton will change with the addition of new components, thereby updating the partially saturated pore fracture medium model.

[0148] In one example, the calculating the longitudinal wave dispersion and attenuation according to the wave propagation dynamics equations includes:

[0149] Step 701: Obtain the wave number of the longitudinal wave according to the wave propagation dynamics equations.

[0150] In this example, in order to solve the wave propagation dynamics equations to obtain the wave number of the P-wave, a series of physical parameter values ​​for each component in the rock physics model are required. These physical parameter values ​​include but are not limited to:

[0151] Rock particle bulk modulus: estimated by the rock mineral composition obtained by X-ray diffraction analysis, it reflects the resistance of rock particles to compression. Rock skeleton modulus: estimated by measuring the longitudinal and shear wave velocities in the saturated state, it represents the elastic properties of the rock skeleton (i.e., the part that does not contain pore fluid). Permeability: determined by the porosity-permeability relationship obtained by experimental measurement, it describes the difficulty of fluid flow in the pores of the rock. Bulk modulus, density and viscosity of the fluid: these parameters are the physical properties of the fluid under actual reservoir conditions. Fracture porosity: estimated by the velocity obtained by the variable confining pressure test, it represents the volume ratio occupied by fractures in the rock. Bulk modulus and shear modulus of fractures and fluid patches: these parameters are determined based on the empirical results obtained by predecessors, they describe the resistance of fractures and fluid patches to compression and shear. Radius parameters and volume fractions of fractures and fluid patches: the radius parameters are determined based on the pore structure parameters, and the volume fraction is related to the scale range of fractures and fluid patches, which can be set and adjusted manually.

[0152] By substituting the specific values ​​of the above parameters into formulas (8a)-(8f) and substituting them into the plane longitudinal wave analytical solution, the wave number k of the longitudinal wave can be derived using the plane wave analysis method.

[0153] Step 702: Calculate the longitudinal wave dispersion and attenuation according to the wave number of the longitudinal wave.

[0154] In this example, the longitudinal wave number k calculated in step 701 is substituted into the following formula to calculate the longitudinal wave dispersion and attenuation:

[0155] (9)

[0156] (10)

[0157] Wherein, the wave number k is a complex number, Im means taking the imaginary part of the complex number, and RE means taking the real part of the complex number; is the angular frequency.

[0158] Embodiment 1:

[0159] In one embodiment, a method for calculating the dispersion and attenuation of longitudinal waves in the partially saturated porous fractured medium is specifically described.

[0160] Assuming rock porosity , crack volume fraction and density 12%, 3% and 2.65g / cm 3 The average bulk modulus of rock mineral particles is 38 GPa, the bulk modulus of the rock dry skeleton and shear modulus The bulk modulus, porosity and permeability of the main rock skeleton are set to 18 GPa, 10% and 0.01D respectively; the bulk modulus, porosity and permeability of the embedded body are set to 1 GPa, 20% and 0.1D respectively. The bulk modulus, viscosity and density of water and gas contained in the pores are 2.5 and 0.05 GPa, 1 and 0.015 mPa·s, 1.04 and 0.117 g / cm 3 Here, it is assumed that the radius distribution of cracks and fluid patches follows the fractal distribution characteristics, and the fractal dimension of cracks and fluid patches is Set to 2.9, the radius range is 0.01-100mm. Different fractal dimensions will cause different degrees of rock P-wave dispersion. Generally, an increase in fractal dimension will lead to a decrease in P-wave velocity. When analyzing the effects of different fractures and fluid parameters on P-wave velocity and attenuation, other parameters remain unchanged.

[0161] See also Figure 8a, This figure shows the change of P-wave velocity and attenuation with frequency at different radius ranges at 90% water saturation. The fractal dimension and radius range of cracks and fluid patches are consistent. When the fractal dimension remains unchanged, the attenuation peak moves to low frequency as the minimum radius range increases.

[0162] See also Figure 8b , which shows the variation of rock P-wave velocity and attenuation with frequency at different saturations. When the main skeleton is saturated with one fluid, the attenuation is related to the waveguide flow between the hard pores of the main skeleton and the soft pores of the embedded body. When the main skeleton is partially saturated with gas and water, a strong attenuation peak appears at a relatively high frequency due to the waveguide flow at the interface of the immiscible fluids.

[0163] See also Figure 8c , the figure shows the change of P-wave velocity and attenuation with water saturation in partially gas-water saturated rocks at different frequencies. At different frequencies, as the water saturation increases, the P-wave velocity decreases first and then increases rapidly. As the frequency increases, the attenuation peak shifts toward low water saturation.

[0164] The present disclosure also provides a system for calculating the dispersion and attenuation of longitudinal waves in a partially saturated porous fracture medium, such as Fig. 9 As shown, the system comprises:

[0165] An acquisition module 901 is used to acquire pore structure parameters in a sample image;

[0166] A construction module 902 is used to construct a partially saturated pore fracture medium according to the pore structure parameters;

[0167] The construction module 902 is further used to construct a dissipation equation, a potential energy equation and a kinetic energy equation of the partially saturated porous fracture medium according to the partially saturated porous fracture medium and component parameters;

[0168] The construction module 902 is further used to construct a group of wave propagation dynamic equations of the partially saturated porous fracture medium according to the dissipation equation, the potential energy equation and the kinetic energy equation;

[0169] The calculation module 903 is used to calculate the longitudinal wave dispersion and attenuation according to the wave propagation dynamics equations.

[0170] In one example, the acquisition module 901 is specifically configured to:

[0171] Acquiring a pore structure in the sample image;

[0172] The pore structure is analyzed by using an image segmentation method to obtain pore distribution characteristics and a probability density distribution histogram;

[0173] According to the pore distribution characteristics, the probability density distribution histogram is fitted using a distribution function to obtain pore structure parameters.

[0174] In one example, when constructing a partially saturated porous fracture medium according to the pore structure parameters, the construction module 902 is specifically used to:

[0175] The preset pore fracture medium model includes the following components: a main skeleton, a first fluid, a second fluid, an embedded body containing fractures, and fluid patches; the main skeleton is partially saturated with the first fluid and the second fluid; the embedded body is saturated with the first fluid;

[0176] The radius parameters characterizing the cracks and fluid patches in the pore structure parameters are discretized into a plurality of components of different sizes, and the cracks and fluid patches of each group are sequentially added into the main skeleton in the order of the radius parameters from large to small;

[0177] Whenever the porosity of the main skeleton meets the preset conditions, the preset pore fracture medium model is used as a partially saturated pore fracture medium.

[0178] In one example, when establishing the dissipation equation of the partially saturated porous fracture medium, the construction module 902 is specifically used to:

[0179] The dissipation equation is established according to the component parameters of the partially saturated porous fracture medium, the Biot dissipation parameters of the fluid in the main skeleton and the embedded body, the waveguide flow dissipation parameters of the first fluid at the interface between the main skeleton and the embedded body, and the waveguide flow dissipation parameters of the first fluid and the second fluid at the interface between the main skeleton.

[0180] In one example, when establishing the potential energy equation of the partially saturated porous fracture medium, the construction module 902 is specifically used to:

[0181] According to the displacement divergence field of the fluid in the main skeleton and the embedded body, the strain energy generated at the interface between the solid, liquid and immiscible fluid in the partially saturated porous fracture medium is calculated to obtain a first potential energy equation;

[0182] The first potential energy equation is coupled with the second potential energy equation to obtain the potential energy equation; the second potential energy equation characterizes the elastic strain energy in the partially saturated porous fracture medium.

[0183] In one example, when establishing the kinetic energy equation of the partially saturated porous fracture medium, the construction module 902 is specifically used to:

[0184] The kinetic energy equation of the partially saturated porous fractured medium is established based on the kinetic energy caused by the global flow in the partially saturated porous fractured medium, the kinetic energy caused by the local flow at the interface between the main skeleton saturated with the first fluid and the embedded body, and the kinetic energy caused by the local flow at the interface between the first fluid and the second fluid at the main skeleton.

[0185] In one example, when constructing the wave propagation dynamics equations of the partially saturated porous fracture medium according to the dissipation equation, the potential energy equation, and the kinetic energy equation, the construction module 902 is specifically used to:

[0186] After each set of component fractures and fluid patches is added to the main skeleton, a dissipation equation, a potential energy equation and a kinetic energy equation of the current partially saturated porous fracture medium are obtained;

[0187] Substituting the dissipation equation, potential energy equation and kinetic energy equation into the Lagrangian formula to obtain the wave propagation dynamics equation group of the current round, and obtaining the elastic modulus of the main skeleton in the next adding operation;

[0188] The above operation is repeated until all the cracks and fluid patches are added into the main skeleton, and the wave propagation dynamic equations of the partially saturated porous fracture medium are obtained.

[0189] In one example, the construction module 902 is also used to obtain the elastic modulus of the main skeleton in the next adding operation, specifically for:

[0190] Based on the plane wave analysis method, the bulk modulus and shear modulus of the saturated immiscible fluid composite medium in the partially saturated porous fracture medium are determined using the wave propagation dynamics equations of the current round;

[0191] Based on Gassmann theory, the elastic modulus of dry rock of the composite medium in the partially saturated porous fracture medium is determined, and the elastic modulus of dry rock of the composite medium is used as the elastic modulus of the main skeleton in the next adding operation.

[0192] In one example, the calculation module 903 is specifically configured to:

[0193] Obtaining the wave number of the longitudinal wave according to the wave propagation dynamics equation group;

[0194] The longitudinal wave dispersion and attenuation are calculated based on the wave number of the longitudinal wave.

[0195] According to an embodiment of the present disclosure, the present disclosure also provides an electronic device and a readable storage medium.

[0196] Fig.10A schematic block diagram of an example electronic device 1000 that can be used to implement an embodiment of the present disclosure is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present disclosure described and / or required herein.

[0197] like Fig.10 As shown, the electronic device 1000 includes a computing unit 1001, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 1002 or a computer program loaded from a storage unit 1008 into a random access memory (RAM) 1003. In the RAM 1003, various programs and data required for the operation of the device 1000 can also be stored. The computing unit 1001, the ROM 1002, and the RAM 1003 are connected to each other via a bus 1004. An input / output (I / O) interface 1005 is also connected to the bus 1004.

[0198] A number of components in the device 1000 are connected to the I / O interface 1005, including: an input unit 1006, such as a keyboard, a mouse, etc.; an output unit 1007, such as various types of displays, speakers, etc.; a storage unit 1008, such as a disk, an optical disk, etc.; and a communication unit 1009, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 1009 allows the device 1000 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.

[0199] The computing unit 1001 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 1001 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The computing unit 1001 performs the various methods and processes described above, such as the calculation method of longitudinal wave dispersion and attenuation in a partially saturated porous fracture medium. For example, in some embodiments, the calculation method of longitudinal wave dispersion and attenuation in a partially saturated porous fracture medium may be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as a storage unit 1008. In some embodiments, part or all of the computer program may be loaded and / or installed on the device 1000 via the ROM 1002 and / or the communication unit 1009. When the computer program is loaded into the RAM 1003 and executed by the computing unit 1001, one or more steps of the method for calculating the dispersion and attenuation of longitudinal waves in a partially saturated porous fracture medium described above may be performed. Alternatively, in other embodiments, the computing unit 1001 may be configured to perform the method for calculating the dispersion and attenuation of longitudinal waves in a partially saturated porous fracture medium in any other appropriate manner (e.g., by means of firmware).

[0200] Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0201] The program code for implementing the method of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that the program code, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The program code may be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0202] In the context of the present disclosure, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or device, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0203] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0204] The systems and techniques described herein may be implemented in a computing system that includes back-end components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes front-end components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such back-end components, middleware components, or front-end components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), and the Internet.

[0205] A computer system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The relationship of client and server is generated by computer programs running on respective computers and having a client-server relationship with each other. The server may be a cloud server, a server of a distributed system, or a server combined with a blockchain.

[0206] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved, and this document does not limit this.

[0207] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0208] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for calculating the dispersion and attenuation of longitudinal waves in partially saturated porous fracture media. It is characterized in that The method comprises: Obtain pore structure parameters in sample images; According to the pore structure parameters, a partially saturated pore fracture medium is constructed; According to the partially saturated porous fractured medium and component parameters, a dissipation equation, a potential energy equation and a kinetic energy equation of the partially saturated porous fractured medium are constructed; According to the dissipation equation, potential energy equation and kinetic energy equation, a group of wave propagation dynamic equations of the partially saturated porous fracture medium is constructed; Calculating the longitudinal wave dispersion and attenuation according to the wave propagation dynamics equations; The step of obtaining the pore structure parameters in the sample image includes: Acquiring a pore structure in the sample image; The pore structure is analyzed by using an image segmentation method to obtain pore distribution characteristics and a probability density distribution histogram; According to the pore distribution characteristics, the probability density distribution histogram is fitted using a distribution function to obtain pore structure parameters; Construct a partially saturated porous fracture medium, including: The preset pore fracture medium model includes the following components: a main skeleton, a first fluid, a second fluid, an embedded body containing fractures, and fluid patches; the main skeleton is partially saturated with the first fluid and the second fluid; the embedded body is saturated with the first fluid; The radius parameters characterizing the cracks and fluid patches in the pore structure parameters are discretized into a plurality of components of different sizes, and the cracks and fluid patches of each group are sequentially added into the main skeleton in the order of the radius parameters from large to small; Whenever the porosity of the main skeleton meets a preset condition, the preset pore fracture medium model is used as a partially saturated pore fracture medium; The dissipation equation of the partially saturated porous fracture medium is established, including: Establishing the dissipation equation according to the component parameters of the partially saturated porous fracture medium, the Biot dissipation parameters of the fluid in the main skeleton and the embedded body, the waveguide flow dissipation parameters of the first fluid at the interface between the main skeleton and the embedded body, and the waveguide flow dissipation parameters of the first fluid and the second fluid at the interface between the main skeleton; The potential energy equation of the partially saturated porous fracture medium is established, including: According to the displacement divergence field of the fluid in the main skeleton and the embedded body, the strain energy generated at the interface between the solid, liquid and immiscible fluid in the partially saturated porous fracture medium is calculated to obtain a first potential energy equation; The first potential energy equation is coupled with the second potential energy equation to obtain the potential energy equation; the second potential energy equation represents the elastic strain energy in the partially saturated porous fracture medium; The kinetic energy equation of the partially saturated porous fracture medium is established, including: A kinetic energy equation of the partially saturated porous fractured medium is established based on the kinetic energy caused by the global flow in the partially saturated porous fractured medium, the kinetic energy caused by the local flow at the interface between the main skeleton saturated with the first fluid and the embedded body, and the kinetic energy caused by the local flow at the interface between the first fluid and the second fluid in the main skeleton; According to the dissipation equation, potential energy equation and kinetic energy equation, a group of wave propagation dynamic equations of the partially saturated porous fracture medium is constructed, including: After each set of component fractures and fluid patches is added to the main skeleton, a dissipation equation, a potential energy equation and a kinetic energy equation of the current partially saturated porous fracture medium are obtained; Substituting the dissipation equation, potential energy equation and kinetic energy equation into the Lagrangian formula to obtain the wave propagation dynamics equation group of the current round, and obtaining the elastic modulus of the main skeleton in the next adding operation; Repeat the above operation until all the cracks and fluid patches are added into the main skeleton, and obtain the wave propagation dynamic equations of the partially saturated porous fracture medium; The step of obtaining the elastic modulus of the main skeleton in the next adding operation includes: Based on the plane wave analysis method, the bulk modulus and shear modulus of the saturated immiscible fluid composite medium in the partially saturated porous fracture medium are determined using the wave propagation dynamics equations of the current round; Based on Gassmann theory, the elastic modulus of dry rock of the composite medium in the partially saturated porous fracture medium is determined, and the elastic modulus of dry rock of the composite medium is used as the elastic modulus of the main skeleton in the next adding operation; The longitudinal wave dispersion and attenuation are calculated according to the wave propagation dynamics equations, including: Obtaining the wave number of the longitudinal wave according to the wave propagation dynamics equation group; The longitudinal wave dispersion and attenuation are calculated based on the wave number of the longitudinal wave.

2. A calculation system for the dispersion and attenuation of longitudinal waves in partially saturated porous fracture media, It is characterized in that The system comprises: An acquisition module, used for acquiring pore structure parameters in a sample image; A construction module, used for constructing a partially saturated pore fracture medium according to the pore structure parameters; The construction module is further used to construct a dissipation equation, a potential energy equation and a kinetic energy equation of the partially saturated porous fracture medium according to the partially saturated porous fracture medium and component parameters; The construction module is also used to construct the wave propagation dynamics equation group of the partially saturated porous fracture medium according to the dissipation equation, the potential energy equation and the kinetic energy equation; A calculation module, for calculating the longitudinal wave dispersion and attenuation according to the wave propagation dynamics equations; Get the module, specifically for: Acquiring a pore structure in the sample image; The pore structure is analyzed by using an image segmentation method to obtain pore distribution characteristics and a probability density distribution histogram; According to the pore distribution characteristics, the probability density distribution histogram is fitted using a distribution function to obtain pore structure parameters; When constructing a partially saturated pore fracture medium according to the pore structure parameters, the construction module is specifically used to: The preset pore fracture medium model includes the following components: a main skeleton, a first fluid, a second fluid, an embedded body containing fractures, and fluid patches; the main skeleton is partially saturated with the first fluid and the second fluid; the embedded body is saturated with the first fluid; The radius parameters characterizing the cracks and fluid patches in the pore structure parameters are discretized into a plurality of components of different sizes, and the cracks and fluid patches of each group are sequentially added into the main skeleton in the order of the radius parameters from large to small; Whenever the porosity of the main skeleton meets a preset condition, the preset pore fracture medium model is used as a partially saturated pore fracture medium; When establishing the dissipation equation of the partially saturated porous fracture medium, the building module is specifically used to: Establishing the dissipation equation according to the component parameters of the partially saturated porous fracture medium, the Biot dissipation parameters of the fluid in the main skeleton and the embedded body, the waveguide flow dissipation parameters of the first fluid at the interface between the main skeleton and the embedded body, and the waveguide flow dissipation parameters of the first fluid and the second fluid at the interface between the main skeleton; When establishing the potential energy equation of the partially saturated porous fracture medium, the building module is specifically used to: According to the displacement divergence field of the fluid in the main skeleton and the embedded body, the strain energy generated at the interface between the solid, liquid and immiscible fluid in the partially saturated porous fracture medium is calculated to obtain a first potential energy equation; The first potential energy equation is coupled with the second potential energy equation to obtain the potential energy equation; the second potential energy equation represents the elastic strain energy in the partially saturated porous fracture medium; When establishing the kinetic energy equation of the partially saturated porous fracture medium, the building module is specifically used to: A kinetic energy equation of the partially saturated porous fractured medium is established based on the kinetic energy caused by the global flow in the partially saturated porous fractured medium, the kinetic energy caused by the local flow at the interface between the main skeleton saturated with the first fluid and the embedded body, and the kinetic energy caused by the local flow at the interface between the first fluid and the second fluid in the main skeleton; When constructing the wave propagation dynamics equations of the partially saturated porous fracture medium according to the dissipation equation, the potential energy equation and the kinetic energy equation, the construction module is specifically used to: After each set of component fractures and fluid patches is added to the main skeleton, a dissipation equation, a potential energy equation and a kinetic energy equation of the current partially saturated porous fracture medium are obtained; Substituting the dissipation equation, potential energy equation and kinetic energy equation into the Lagrangian formula to obtain the wave propagation dynamics equation group of the current round, and obtaining the elastic modulus of the main skeleton in the next adding operation; Repeat the above operation until all the cracks and fluid patches are added into the main skeleton, and obtain the wave propagation dynamic equations of the partially saturated porous fracture medium; The construction module is also used to obtain the elastic modulus of the main skeleton in the next adding operation, specifically for: Based on the plane wave analysis method, the bulk modulus and shear modulus of the saturated immiscible fluid composite medium in the partially saturated porous fracture medium are determined using the wave propagation dynamics equations of the current round; Based on Gassmann theory, the elastic modulus of dry rock of the composite medium in the partially saturated porous fracture medium is determined, and the elastic modulus of dry rock of the composite medium is used as the elastic modulus of the main skeleton in the next adding operation; The computing module is specifically used for: Obtaining the wave number of the longitudinal wave according to the wave propagation dynamics equation group; The longitudinal wave dispersion and attenuation are calculated based on the wave number of the longitudinal wave.

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