Hydrate Core Dynamic Permeability Calculation Method and Related Equipment

Abstract

The present invention discloses a method for calculating the dynamic permeability of a hydrate core and related equipment, which relates to the calculation of core permeability and mainly solves the problem that there is currently no method for calculating the change process of permeability caused by the dynamic changes of hydrate decomposition and multiphase fluid transport in a hydrate core. The method includes: determining a digital core model based on the hydrate core, wherein the digital core model includes a hydrate part and a pore part. Determining a transport mechanism model for each phase fluid to pass through the hydrate part and the pore part based on the digital core model and the parameters of each phase fluid; determining a dynamic permeability change curve of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the digital core model and the transport mechanism model, wherein the saturation is a volume fraction. The present invention is used in the process of calculating the dynamic permeability of a hydrate core.

Description

Technical Field

[0001] The present invention relates to the calculation of core permeability, and particularly to a method for calculating the dynamic permeability of hydrate cores and related equipment. Background Art

[0002] Natural gas hydrate is a clean energy source existing in marine sediments and permafrost areas. It has the advantages of large reserves and high combustion efficiency and is considered an important alternative resource to traditional fossil fuels. In-depth understanding of the dissociation and migration mechanisms of natural gas hydrates in porous media is crucial for the commercial and efficient development of natural gas hydrates. Under formation conditions, the in-situ thermodynamic stable state of natural gas hydrate is solid, but it will release gas (mainly methane) and water under standard temperature and pressure conditions (STP), which makes the coring and laboratory testing of natural hydrates costly and time-consuming, and it is difficult to obtain the multiple physical, chemical, and thermodynamic properties of natural gas hydrate (MH) sediments, thus restricting the prediction and optimization of MH production.

[0003] In previous studies, researchers mainly used micro-CT technology to visualize the process of hydrate formation or dissociation. There has been no study that simultaneously provides the seepage characteristics of multiphase fluids in the core. Moreover, in these visualization experiments, it is difficult to capture and distinguish the migration mechanisms of methane and water in multiphase fluids. Therefore, the current studies are single-phase or two-phase flows that do not consider the hydrate decomposition-transport mechanism, and thus cannot reflect the dynamic coupling mechanism of hydrate decomposition and multiphase fluid transport in hydrate cores. Summary of the Invention

[0004] In view of the above problems, the present invention provides a method for calculating the dynamic permeability of hydrate cores and related equipment, mainly aiming to solve the problem that there is currently a lack of a method for calculating the change process of permeability caused by the dynamic changes of hydrate decomposition and multiphase fluid transport in hydrate cores.

[0005] To solve the above-mentioned at least one technical problem, in a first aspect, the present invention provides a method for calculating the dynamic permeability of hydrate cores, the method comprising:

[0006] Determining a digital core model based on a hydrate core, wherein the digital core model includes a hydrate part and a pore part.

[0007] Determining a transport mechanism model of each phase fluid passing through the hydrate part and the pore part based on the digital core model and the parameters of each phase fluid;

[0008] Determining a dynamic permeability change curve of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the digital core model and the transport mechanism model, wherein the saturation is a volume fraction.

[0009] Optionally, the above-mentioned method for determining a digital core model based on a hydrate core includes:

[0010] Under the condition that the temperature and pressure ensure the stability of the hydrate in the above-mentioned core, obtaining a CT image of the hydrate core based on CT scanning technology;

[0011] Constructing an initial digital core model based on the above-mentioned CT image of the hydrate core;

[0012] Adding flow field extension regions to the inlet and outlet of the above-mentioned initial digital core model respectively to determine the above-mentioned digital core model;

[0013] Among them, the above-mentioned digital core model parameters include model size, model porosity, initial hydrate saturation, number of digital core grids, and core permeability without hydrate.

[0014] Optionally, the above-mentioned method for determining the transport mechanism model of each phase fluid passing through the above-mentioned hydrate part based on the above-mentioned digital core model and each phase fluid parameter includes:

[0015] Determining the above-mentioned digital core model parameters and each phase fluid parameter, where the above-mentioned each phase fluid parameter includes fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity;

[0016] Based on the above-mentioned digital core model parameters and each phase fluid parameter, determining the transport mechanism model of the above-mentioned hydrate part through the enthalpy change equation, CK equation, and momentum source term.

[0017] Optionally, the above-mentioned method for determining the transport mechanism model of each phase fluid passing through the above-mentioned pore part based on the above-mentioned digital core model and each phase fluid parameter includes:

[0018] Determining the above-mentioned digital core model parameters and each phase fluid parameter, where the above-mentioned each phase fluid parameter includes fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity;

[0019] Based on the above-mentioned digital core model parameters and each phase fluid parameter, determining the transport mechanism model of the above-mentioned pore part through the VOF model and NS equation.

[0020] Optionally, the above-mentioned method further includes:

[0021] Setting initial conditions for the above-mentioned digital core model based on the hydrate decomposition condition and the hydrate phase equilibrium curve,

[0022] Among them, the above-mentioned hydrate phase equilibrium curve is a curve for characterizing the change of temperature and pressure conditions required for the hydrate to maintain a solid state or decompose into a water and gas state,

[0023] The above initial conditions include the inlet water flow rate, the inlet water temperature, the wall temperature, the initial temperature of the fluid domain, and the initial pressure of the fluid domain.

[0024] Optionally, the above method further includes:

[0025] Performing single-phase fluid seepage based on the above digital core model and the above transport mechanism model to determine the initial flow field parameters, where the above initial flow field parameters include the flow field pressure, the flow field temperature, and the fluid velocity within the flow field.

[0026] Optionally, determining the variation curve of the dynamic permeability of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the above digital core model and the above transport mechanism model includes:

[0027] Determining the variation curve of the absolute permeability of the hydrate core and the variation curve of the dynamic permeability of the multiphase fluid at different hydrate saturations during the hydrate decomposition process in the core based on the above initial flow field parameters, the above digital core model, and the above transport mechanism model, where the above multiphase fluid includes water and methane.

[0028] In a second aspect, an embodiment of the present invention further provides a device for calculating the dynamic permeability of a hydrate core, including:

[0029] A determination unit for determining a digital core model based on the hydrate core, where the above digital core model includes a hydrate part and a pore part.

[0030] A second determination unit for determining a transport mechanism model of each phase fluid passing through the above hydrate part and the above pore part based on the above digital core model and the parameters of each phase fluid;

[0031] A third determination unit for determining the variation curve of the dynamic permeability of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the above digital core model and the above transport mechanism model, where the above saturation is a volume fraction.

[0032] To achieve the above object, according to a third aspect of the present invention, there is provided a computer-readable storage medium, where the above computer-readable storage medium includes a stored program, and when the above program is executed by a processor, the steps of the above method for calculating the dynamic permeability of a hydrate core are implemented.

[0033] To achieve the above object, according to a fourth aspect of the present invention, there is provided an electronic device, including at least one processor and at least one memory connected to the above processor; where the above processor is used to call program instructions in the above memory to execute the steps of the above method for calculating the dynamic permeability of a hydrate core.

[0034] With the above technical solution, for the problem that there is currently a lack of a method for calculating the change process of permeability caused by the dynamic changes of hydrate decomposition and multiphase fluid transport in hydrate cores, the present invention determines a digital core model based on the hydrate core, wherein the digital core model includes a hydrate part and a pore part. Based on the digital core model and the parameters of each phase of fluid, a transport mechanism model for each phase of fluid passing through the hydrate part and the pore part is determined; based on the digital core model and the transport mechanism model, a dynamic permeability change curve of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core is determined, wherein the saturation is a volume fraction. In the above solution, due to the reconstruction and assembly of the digital model based on the hydrate core, the hydrate part and the pore part of the digital core model, including the hydrate core, are accurately restored. Since the transport mechanism model of each phase of fluid passing through the hydrate part and the pore part is simulated, the dynamic distribution and changes of hydrates, methane, and water in the porous medium are determined. Combining the real-time evolution laws of temperature, pressure, and fluid velocity fields, the effects of injection water temperature, pressure, and rate on hydrate decomposition and migration are analyzed and discussed, so as to effectively predict the dynamic permeability change process during the hydrate decomposition process in rock pores. It can be understood that natural gas hydrates are simply referred to as hydrates in this solution.

[0035] Correspondingly, the hydrate core dynamic permeability calculation device, equipment, and computer-readable storage medium provided by the embodiments of the present invention also have the above technical effects.

[0036] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention are specifically described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0038] Figure 1 A schematic flow chart of a method for calculating the dynamic permeability of a hydrate core provided by an embodiment of the present invention is shown;

[0039] Figure 2 A micro-CT image of a hydrate core provided by an embodiment of the present invention is shown;

[0040] Figure 3 Shows a digital core model of a hydrate core provided by an embodiment of the present invention and its boundary conditions;

[0041] Figure 4 Shows the initial conditions of the flow field adopted by a digital core model of a hydrate core provided by an embodiment of the present invention and the boundary conditions for simulating the pressure reduction or heat injection extraction of hydrates;

[0042] Figure 5 Shows the temperature distribution nephogram of hydrates and methane during the decomposition process of a hydrate core provided by an embodiment of the present invention;

[0043] Figure 6 Shows the saturation curves of hydrates, water, and methane at different time points of a hydrate core provided by an embodiment of the present invention;

[0044] Figure 7 Shows the change curves of the absolute permeability of the core and the dynamic permeability of multiphase fluids under different hydrate saturation conditions provided by an embodiment of the present invention;

[0045] Figure 8 Shows a schematic block diagram of the composition of a device for calculating the dynamic permeability of a hydrate core provided by an embodiment of the present invention;

[0046] Figure 9 Shows a schematic block diagram of the composition of an electronic device for calculating the dynamic permeability of a hydrate core provided by an embodiment of the present invention. Detailed implementation manners

[0047] Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art.

[0048] In order to solve the problem that there is currently a lack of a method for calculating the change process of permeability caused by the dynamic changes of hydrate decomposition and multiphase fluid transport in a hydrate core, an embodiment of the present invention provides a method for calculating the dynamic permeability of a hydrate core, as Figure 1 shown, the method includes:

[0049] S101. Determine a digital core model based on the hydrate core, where the digital core model includes a hydrate part and a pore part.

[0050] Exemplarily, the method first determines a physical hydrate core, scans the hydrate core to obtain its digital model, and can use structured grid modeling technology to achieve three-dimensional reconstruction and assembly of the grids in the hydrate and pore regions, and save them in the.inp file format.

[0051] S102. Determine the transport mechanism models of the above-mentioned fluid phases passing through the above-mentioned hydrate part and the above-mentioned pore part based on the above-mentioned digital core model and the fluid parameter of each phase;

[0052] Exemplarily, the method simulates the dynamic distribution and transport mechanism of hydrates, methane, and water in a real porous medium. Since the transport mechanism models of each fluid phase passing through the above-mentioned hydrate part and the above-mentioned pore part are simulated, the dynamic distribution and changes of hydrates, methane, and water in the porous medium are determined. Combining with the real-time evolution laws of temperature, pressure, and fluid velocity fields, the effects of water injection temperature, pressure, and rate on hydrate decomposition and migration are analyzed and discussed.

[0053] S103. Determine the dynamic permeability change curve of the above-mentioned hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the above-mentioned digital core model and the above-mentioned transport mechanism model, where the above-mentioned saturation is the volume fraction.

[0054] Exemplarily, through this method, the change of the dynamic permeability of the above-mentioned hydrate core at different hydrate saturations during the hydrate decomposition process in the rock pores can be effectively predicted.

[0055] With the above technical solution, the method for calculating the dynamic permeability of hydrate cores provided by the present invention addresses the problem that there is currently a lack of a method for calculating the change process of permeability caused by the dynamic changes during the decomposition of hydrates and the transport of multiphase fluids in hydrate cores. The present invention determines a digital core model based on the hydrate core, wherein the digital core model includes a hydrate part and a pore part. Based on the digital core model and the parameters of each phase of fluid, a transport mechanism model for each phase of fluid passing through the hydrate part and the pore part is determined; based on the digital core model and the transport mechanism model, a dynamic permeability change curve of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core is determined, wherein the saturation is the volume fraction. In the above solution, due to the reconstruction and assembly of the digital model based on the hydrate core, the hydrate part and the pore part of the hydrate core are accurately restored in the digital core model. Since the transport mechanism model of each phase of fluid passing through the hydrate part and the pore part is simulated, the dynamic distribution and changes of hydrates, methane, and water in the porous medium are determined. Combining the real-time evolution laws of temperature, pressure, and fluid velocity fields, the effects of injection water temperature, pressure, and rate on hydrate decomposition and migration are analyzed and discussed, thereby effectively predicting the dynamic permeability change process during the hydrate decomposition process in the rock pores.

[0056] In one embodiment, the determining the digital core model based on the hydrate core includes:

[0057] Under the condition of ensuring that the temperature and pressure keep the hydrates in the core stable, a CT image of the hydrate core is obtained based on CT scanning technology;

[0058] An initial digital core model is constructed based on the CT image of the hydrate core;

[0059] Flow field extension regions are respectively added to the inlet and outlet of the initial digital core model to determine the digital core model;

[0060] Among them, the digital core model parameters include model size, model porosity, initial hydrate saturation, digital core grid number, and core permeability without hydrates.

[0061] Exemplarily, in this method, micro-CT scanning of the hydrate core is carried out. During the scanning process, the temperature and pressure conditions of the core are ensured to keep the hydrates in a stable state to obtain the gray value characteristics of the skeleton, hydrates, and pore space in the hydrate core. Combining technologies such as noise reduction and multi-threshold image segmentation, image recognition and reconstruction of mineral particles, hydrate solids, and pores in the micro-CT image are realized. The CT image of the obtained hydrate core is as Figure 2As shown, it includes a cross-sectional image (left) and a 3D view (right). Then, using the structured grid modeling technique, the 3D reconstruction and assembly of the hydrate and pore region grids are realized and saved in the.inp file format.

[0062] Exemplarily, in order to improve the convergence and stability of the simulation calculation, the inlet and outlet sections of the hydrate core in the simulation are respectively extended, and the extended regions are used as flow field buffer zones to ensure the accuracy of the above digital core model.

[0063] Exemplarily, the reconstructed grid assembly model is imported into ICEM to complete the surface mesh reconstruction of the reconstructed volume element. The surface meshes and volume meshes of different fluid domains required in the simulation are grouped and named. After the grid quality inspection, the.msh file format recognized by the numerical simulation software Fluent is exported, and the generated digital core model and its boundary conditions are as Figure 3 shown, where Figure 3 the left rectangular region in the figure is the inlet flow field buffer zone, the right rectangular region is the outlet flow field buffer zone (i.e., the flow field extended region in the figure), the black part is the pore part, the gray part is the hydrate part, and the flow direction simulated by this method in the figure is from left to right. Among them, Vin at the inlet is the inlet water flow velocity of the model, P is the initial pressure of the fluid domain, Tin is the inlet water temperature of the model and the outlet boundary temperature of the model, P at the outlet is the initial pressure of the fluid domain, and a no-slip free heat transfer boundary is set between the hydrate and the pores, and Tw is the model wall temperature.

[0064] Exemplarily, the following table lists a digital core model parameter table (the parameters in the table are examples for reference only).

[0065]

[0066] In one embodiment, the above transport mechanism model for each phase fluid passing through the above hydrate part is determined based on the above digital core model and each phase fluid parameter, including:

[0067] Determine the above digital core model parameters and each phase fluid parameters, where the above each phase fluid parameters include fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity;

[0068] Based on the above digital core model parameters and each phase fluid parameters, the transport mechanism model of the above hydrate part is determined through the enthalpy change equation, CK equation, and momentum source term.

[0069] Exemplarily, the following table lists a table of each phase fluid parameters (the parameters in the table are examples for reference only).

[0070]

[0071] Exemplarily, the hydrate part is considered as a hypothetical porous medium, and its porosity depends on the space generated after hydrate decomposition. When the hydrate is not completely decomposed, the energy and fluid transport mechanisms in the porous medium follow the enthalpy change equation and the classical CK equation, and the C-language compilation of the above mathematical model is realized in the form of UDF. Water is considered an incompressible fluid, and methane gas is a compressible gas following the PR equation. Thus, it is convenient to perform simulations based on the transport mechanism model of the hydrate part later.

[0072] In one embodiment, the above-mentioned transport mechanism model for determining the passage of each phase of fluid through the pore part based on the above-mentioned digital core model and each phase of fluid parameters includes:

[0073] Determine the above-mentioned digital core model parameters and each phase of fluid parameters, where the above-mentioned each phase of fluid parameters includes fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity;

[0074] Based on the above-mentioned digital core model parameters and each phase of fluid parameters, determine the transport mechanism model of the pore part through the VOF model and the NS equation.

[0075] Exemplarily, the pore region without hydrate is a fluid free-flow channel, and the multiphase fluid in the pores follows the volume fraction (VOF) model in Fluent and follows the NS basic equations. When the hydrate is completely decomposed, the original hydrate region degenerates from a porous medium to a pore channel and also follows the NS equation. Exemplarily, the equation is as follows.

[0076]

[0077]

[0078]

[0079] Among them, μ and ρ are the viscosity and density volume average values of each phase of fluid in the unit grid, α i , ρ i , are the volume fraction, density, and velocity vector of the i-th phase fluid respectively, is the velocity vector, m ij is the mass transfer source term from the i-th phase fluid to the j-th phase fluid, is the gravitational acceleration, S m is the mass source term due to the hydrate decomposition reaction, H is the enthalpy change of the multiphase fluid; λe is the thermal conductivity; S E is the energy source term due to the hydrate decomposition reaction, and the momentum source term is:

[0080]

[0081] Among them, K e is the effective porosity of the chemical reaction region containing phase change, following the classical Carman-Koseny equation, is the velocity vector, and A pseudo is the porous medium constant, which determines the damping amplitude during the process of the fluid velocity dropping to 0. Thus, it is convenient for subsequent simulation based on the transport mechanism model of the pore part.

[0082] The decomposition process of natural gas hydrate follows the following formula:

[0083] CH 4 ·N h H 2 O → CH 4 +N h H 2 O

[0084] Among them, the generated gas follows the Peng-Robinson equation, and the generation rate of the reaction product obtained based on the Arrhenius chemical kinetics model is:

[0085]

[0086] Among them, the above-mentioned A r is the reaction factor, E r is the reaction activation energy, R is the universal gas constant, T is the temperature, β r is the temperature exponent, and M r is the molar molecular mass of the reaction product r; according to the reaction process and the generation rate, a chemical reaction mathematical model is obtained, and the chemical reaction mathematical model is compiled to obtain the mass source term.

[0087] The enthalpy change of the multiphase fluid is determined as

[0088]

[0089] Among them, the above-mentioned H i is the enthalpy of the i-th phase fluid in the unit grid, and S E is the energy source term caused by the hydrate decomposition reaction;

[0090] The energy source term is determined as:

[0091] S E =-m r ΔH d ,

[0092] Among them, the above-mentioned H d is the latent heat of the chemical reaction.

[0093] In one embodiment, the above method further includes:

[0094] Setting initial conditions for the above digital core model based on hydrate decomposition conditions and the hydrate phase equilibrium curve,

[0095] wherein the above hydrate phase equilibrium curve is a curve for characterizing the variation of temperature and pressure conditions required for hydrates to maintain a solid state or decompose into water and gas states,

[0096] The above initial conditions include inlet water flow rate, inlet water temperature, wall temperature, initial temperature of the fluid domain, and initial pressure of the fluid domain.

[0097] Exemplarily, Figure 4 The initial conditions of the flow field adopted by the present method and the boundary conditions (i.e., the hydrate phase equilibrium curve) for simulating hydrate pressure reduction or thermal injection production are shown. The hydrate phase equilibrium curve reflects the temperature and pressure conditions required for natural gas hydrates to maintain a solid state or decompose into water and gas. The abscissa in the figure is pressure (MPa), and the ordinate is temperature (K). The curves in the figure include the hydrate phase equilibrium curve, the freezing point of water, the conditions for hydrate pressure reduction production, and the conditions for hydrate thermal injection production. Import the grid file and UDF file into the Fluent simulation software. According to the hydrate decomposition conditions and the hydrate phase equilibrium curve, set the initial conditions of the digital core model. The interface between the hydrate and the pores in the model is set to the interior condition to ensure that the water and methane generated after hydrate decomposition can freely transfer mass and heat with the fluid in the pores. The following table lists the initial condition parameter table (the parameters in the table are examples for reference only).

[0098]

[0099] Through the above hydrate decomposition conditions and the hydrate phase equilibrium curve, the present method is simulated during the hydrate decomposition process to obtain more accurate data.

[0100] In one embodiment, the above method further includes:

[0101] Performing single-phase fluid seepage based on the above digital core model and the above transport mechanism model to determine the initial flow field parameters, wherein the above initial flow field parameters include flow field pressure, flow field temperature, and fluid velocity within the flow field.

[0102] Exemplarily, to improve the smooth convergence and calculation accuracy of the present method, single-phase fluid seepage simulation in the digital core assembly model is first carried out. The above single-phase fluid seepage simulation can use water as the simulated fluid, and the converged flow field calculation result is used as the initial value of the calculation region.

[0103] In one embodiment, determining the variation curve of the dynamic permeability of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the above digital core model and the above transport mechanism model includes:

[0104] Determining the variation curve of the absolute permeability of the hydrate core and the variation curve of the dynamic permeability of the multiphase fluid at different hydrate saturations during the hydrate decomposition process in the core based on the above initial flow field parameters, the above digital core model, and the above transport mechanism model, where the above multiphase fluid includes water and methane.

[0105] Exemplarily, perform numerical simulation calculations on the decomposition of natural gas hydrates and the transport of multiphase fluids at the pore scale in porous media. During the simulation process, record the distribution characteristics of the volume fractions of each phase of hydrate and methane, the velocity field, the pressure field, the temperature field in the porous media at different time points, and the outlet flow rates of each phase at the outlet. The distribution characteristics of the temperature field are as Figure 5 shown, where t represents time, the left legend represents temperature, a is the hydrate saturation, b is the methane saturation, and c is the temperature distribution. The saturation (volume fraction of each phase) curves of hydrate, water, and methane at different time points are as Figure 6 shown, where Tin = 280K represents the temperature of the water at the inlet of the model, Tin = 275K represents the temperature at the outlet boundary of the model, the Sh curve represents the saturation curve of hydrate, the Sw curve represents the saturation curve of water, and the Sm curve represents the saturation curve of methane. Combining with the classical Darcy's law, based on the physical properties of each phase fluid and the size parameters of the digital core model, the evolution curves of the absolute permeability of the core and the dynamic permeability of the multiphase fluid (water and methane) under different hydrate saturation conditions during the hydrate decomposition process in the core can be calculated. The variation curve of the absolute permeability of the above hydrate core and the variation curve of the dynamic permeability of the multiphase fluid (water and methane) are as Figure 7 shown, where the abscissa is the saturation of natural gas hydrate and the ordinate is the permeability. The change in the saturation of natural gas hydrate in the figure should be a gradually decreasing process from right to left as the core decomposes. The figure reflects the change curves of absolute permeability, water phase permeability, and methane permeability.

[0106] Exemplarily, the absolute permeability is the permeability measured when there is only one single-phase fluid in the core, the core does not undergo any physical and chemical reactions with the rock, and the flow of the fluid conforms to Darcy's law.

[0107] Furthermore, as an implementation of the above Figure 1 shown method, an embodiment of the present invention also provides a device for calculating the dynamic permeability of a hydrate core, which is used for the above Figure 1The method shown above is implemented. The device embodiment corresponds to the foregoing method embodiment. For the convenience of reading, the details in the foregoing method embodiment will not be described one by one in this device embodiment. However, it should be clear that the device in this embodiment can correspondingly implement all the contents in the foregoing method embodiment. As Figure 8 shown, the device includes: a determination unit 21, a second determination unit 22, and a third determination unit 23, where

[0108] The determination unit 21 is configured to determine a digital core model based on a hydrate core, where the digital core model includes a hydrate part and a pore part.

[0109] The second determination unit 22 is configured to determine a transport mechanism model of each phase fluid passing through the hydrate part and the pore part based on the digital core model and each phase fluid parameter;

[0110] The third determination unit 23 is configured to determine a dynamic permeability change curve of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the digital core model and the transport mechanism model, where the saturation is a volume fraction.

[0111] Exemplarily, the determining the digital core model based on the hydrate core includes:

[0112] Under the condition of ensuring that the temperature and pressure make the hydrate in the core stable, obtaining a CT image of the hydrate core based on CT scanning technology;

[0113] Constructing an initial digital core model based on the CT image of the hydrate core;

[0114] Adding flow field extension regions to the inlet and outlet of the initial digital core model respectively to determine the digital core model;

[0115] Wherein, the digital core model parameters include model size, model porosity, initial hydrate saturation, digital core grid number, and core permeability without hydrate.

[0116] Exemplarily, the determining the transport mechanism model of each phase fluid passing through the hydrate part based on the digital core model and each phase fluid parameter includes:

[0117] Determining the digital core model parameters and each phase fluid parameter, where the each phase fluid parameter includes fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity;

[0118] Determining the transport mechanism model of the hydrate part based on the digital core model parameters and each phase fluid parameter through the enthalpy change equation, the CK equation, and the momentum source term.

[0119] Exemplarily, the above-mentioned transport mechanism model for determining the transport of each phase of fluid through the pore part based on the above-mentioned digital core model and the parameters of each phase of fluid includes:

[0120] Determine the parameters of the above-mentioned digital core model and the parameters of each phase of fluid, where the parameters of each phase of fluid include fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity;

[0121] Based on the parameters of the above-mentioned digital core model and the parameters of each phase of fluid, determine the transport mechanism model of the pore part through the VOF model and the NS equation.

[0122] Exemplarily, the above-mentioned unit is further configured to:

[0123] Set initial conditions for the above-mentioned digital core model based on the hydrate decomposition conditions and the hydrate phase equilibrium curve,

[0124] where the above-mentioned hydrate phase equilibrium curve is a curve for characterizing the change of temperature and pressure conditions required for the hydrate to remain in a solid state or decompose into a water and gas state,

[0125] The above-mentioned initial conditions include the inlet water flow rate, the inlet water temperature, the wall temperature, the initial temperature of the fluid domain, and the initial pressure of the fluid domain.

[0126] Exemplarily, the above-mentioned unit is further configured to:

[0127] Perform single-phase fluid seepage based on the above-mentioned digital core model and the above-mentioned transport mechanism model to determine the initial flow field parameters, where the above-mentioned initial flow field parameters include the flow field pressure, the flow field temperature, and the fluid velocity in the flow field.

[0128] Exemplarily, the above-mentioned method for determining the change curve of the dynamic permeability of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the above-mentioned digital core model and the above-mentioned transport mechanism model includes:

[0129] Based on the above-mentioned initial flow field parameters, the above-mentioned digital core model, and the above-mentioned transport mechanism model, determine the change curve of the absolute permeability of the hydrate core and the change curve of the dynamic permeability of the multiphase fluid at different hydrate saturations during the hydrate decomposition process in the core, where the above-mentioned multiphase fluid includes water and methane.

[0130] With the above technical solution, the hydrate core dynamic permeability calculation device provided by the present invention addresses the problem that there is currently a lack of a method for calculating the change process of permeability caused by the dynamic changes during hydrate decomposition and multiphase fluid transport in a hydrate core. The present invention determines a digital core model based on the hydrate core, where the digital core model includes a hydrate part and a pore part. Based on the digital core model and the parameters of each phase of fluid, a transport mechanism model for each phase of fluid passing through the hydrate part and the pore part is determined; based on the digital core model and the transport mechanism model, a dynamic permeability change curve of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core is determined, where the saturation is a volume fraction. In the above solution, due to the reconstruction and assembly of the digital model based on the hydrate core, the hydrate part and the pore part of the hydrate core in the digital core model are accurately restored. Since the transport mechanism model of each phase of fluid passing through the hydrate part and the pore part is simulated, the dynamic distribution and change of hydrate, methane, and water in the porous medium are determined. Combining with the real-time evolution laws of temperature, pressure, and fluid velocity fields, the effects of injection water temperature, pressure, and rate on hydrate decomposition and migration are analyzed and discussed, thus effectively predicting the dynamic permeability change process during the hydrate decomposition process in the rock pores.

[0131] The processor contains a kernel, and the kernel retrieves the corresponding program unit from the memory. One or more kernels can be set, and by adjusting the kernel parameters, a method for calculating the dynamic permeability of a hydrate core is implemented, which can solve the problem that there is currently a lack of a method for calculating the change process of permeability caused by the dynamic changes during hydrate decomposition and multiphase fluid transport in a hydrate core.

[0132] The embodiment of the present invention provides a computer-readable storage medium, and the computer-readable storage medium includes a stored program, and when the program is executed by a processor, the above method for calculating the dynamic permeability of a hydrate core is implemented.

[0133] The embodiment of the present invention provides a processor, and the processor is used to run a program, where when the program runs, the above method for calculating the dynamic permeability of a hydrate core is executed.

[0134] The embodiment of the present invention provides an electronic device, and the electronic device includes at least one processor and at least one memory connected to the processor; wherein, the processor is used to call the program instructions in the memory and execute the method for calculating the dynamic permeability of a hydrate core as described above

[0135] The embodiment of the present invention provides an electronic device 30, such as Figure 9As shown in the figure, the electronic device includes at least one processor 301, at least one memory 302 connected to the processor, and a bus 303; among them, the processor 301 and the memory 302 communicate with each other through the bus 303; the processor 301 is used to call program instructions in the memory to execute the above-mentioned method for calculating the dynamic permeability of hydrate cores.

[0136] The intelligent electronic device in this article can be a PC, PAD, mobile phone, etc.

[0137] This application also provides a computer program product, which is suitable for executing a program initialized with the following method steps when executed on a process management electronic device:

[0138] Determine a digital core model based on the hydrate core, where the above digital core model includes a hydrate part and a pore part.

[0139] Determine the transport mechanism model of each phase fluid passing through the above hydrate part and the above pore part based on the above digital core model and each phase fluid parameter;

[0140] Determine the dynamic permeability change curve of the above hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the above digital core model and the above transport mechanism model, where the above saturation is the volume fraction.

[0141] Furthermore, the above determining a digital core model based on the hydrate core includes:

[0142] Under the condition of ensuring that the temperature and pressure make the hydrate in the above core stable, obtain the CT image of the hydrate core based on the CT scanning technology;

[0143] Construct an initial digital core model based on the above CT image of the hydrate core;

[0144] Add flow field extension regions to the inlet and outlet of the above initial digital core model respectively to determine the above digital core model;

[0145] Among them, the above digital core model parameters include model size, model porosity, initial hydrate saturation, number of digital core grids, and core permeability without hydrate.

[0146] Furthermore, the above determining the transport mechanism model of each phase fluid passing through the above hydrate part based on the above digital core model and each phase fluid parameter includes:

[0147] Determine the above digital core model parameters and the above each phase fluid parameters, where the above each phase fluid parameters include fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity;

[0148] Based on the above digital core model parameters and the parameters of each phase of fluid, determine the transport mechanism model of the above hydrate part through the enthalpy change equation, CK equation and momentum source term.

[0149] Further, the above method for determining the transport mechanism model of each phase of fluid passing through the above pore part based on the above digital core model and the parameters of each phase of fluid includes:

[0150] Determine the above digital core model parameters and the parameters of each phase of fluid, where the parameters of each phase of fluid include fluid name, fluid density, fluid viscosity, fluid thermal conductivity and fluid specific heat capacity;

[0151] Based on the above digital core model parameters and the parameters of each phase of fluid, determine the transport mechanism model of the above pore part through the VOF model and NS equation.

[0152] Further, the above method also includes:

[0153] Set initial conditions for the above digital core model based on the hydrate decomposition conditions and the hydrate phase equilibrium curve,

[0154] where the above hydrate phase equilibrium curve is a curve for characterizing the change of temperature and pressure conditions required for the hydrate to remain in a solid state or decompose into a water and gas state,

[0155] The above initial conditions include inlet water flow rate, inlet water temperature, wall temperature, initial temperature of the fluid domain, and initial pressure of the fluid domain.

[0156] Further, the above method also includes:

[0157] Perform single-phase fluid seepage based on the above digital core model and the above transport mechanism model to determine the initial flow field parameters, where the above initial flow field parameters include flow field pressure, flow field temperature and fluid velocity within the flow field.

[0158] Further, the above method for determining the change curve of the dynamic permeability of the above hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the above digital core model and the above transport mechanism model includes:

[0159] Based on the above initial flow field parameters, the above digital core model and the above transport mechanism model, determine the change curve of the absolute permeability of the above hydrate core and the change curve of the dynamic permeability of the multiphase fluid at different hydrate saturations during the hydrate decomposition process in the core, where the above multiphase fluid includes water and methane.

[0160] This application is described with reference to the flowcharts and / or block diagrams of methods, electronic devices (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable process management electronic devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable process management electronic devices generate means for implementing the functions specified in one process Figure 1 one process or multiple processes and / or blocks Figure 1 or means for implementing the functions specified in multiple blocks.

[0161] In a typical configuration, an electronic device includes one or more processors (CPUs), a memory, and a bus. The electronic device may also include an input / output interface, a network interface, etc.

[0162] The memory may include non-permanent memory in the form of computer-readable media, random access memory (RAM), and / or non-volatile memory such as read-only memory (ROM) or flash memory (flash RAM). The memory includes at least one storage chip. The memory is an example of computer-readable media.

[0163] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can store information by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer-readable storage media for a computer include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory, or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD), or other optical storage, magnetic cassette tapes, magnetic tape magnetic disk storage, or other magnetic storage electronic devices, or any other non-transmission media that can be used to store information accessible by a computing electronic device. As defined herein, computer-readable media does not include transitory computer-readable media, such as modulated data signals and carrier waves.

[0164] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, commodity or electronic device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, commodity or electronic device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, commodity or electronic device comprising the element.

[0165] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, system or computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0166] The above are only the embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A method for calculating the dynamic permeability of a hydrate core, characterized in that, it includes: Determining a digital core model based on the hydrate core, wherein the digital core model includes a hydrate part and a pore part; Determining a transport mechanism model for each phase fluid passing through the hydrate part and the pore part based on the digital core model and each phase fluid parameter; Determining a curve of the dynamic permeability change of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the digital core model and the transport mechanism model, wherein the saturation is a volume fraction; The determining the digital core model based on the hydrate core includes: Under the condition of ensuring that the temperature and pressure keep the hydrate in the core stable, obtaining a CT image of the hydrate core based on CT scanning technology; Constructing an initial digital core model based on the CT image of the hydrate core; Adding flow field extension regions to the inlet and outlet of the initial digital core model respectively to determine the digital core model; Wherein, the digital core model parameters include model size, model porosity, initial hydrate saturation, number of digital core grids, and core permeability without hydrate; The determining the transport mechanism model for each phase fluid passing through the hydrate part based on the digital core model and each phase fluid parameter includes: Determining the digital core model parameters and each phase fluid parameter, wherein each phase fluid parameter includes fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity; Determining the transport mechanism model of the hydrate part based on the digital core model parameters and each phase fluid parameter through the enthalpy change equation, CK equation, and momentum source term; The determining the transport mechanism model for each phase fluid passing through the pore part based on the digital core model and each phase fluid parameter includes: Determining the digital core model parameters and each phase fluid parameter, wherein each phase fluid parameter includes fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity; Determining the transport mechanism model of the pore part based on the digital core model parameters and each phase fluid parameter through the VOF model and NS equation.

2. The method according to claim 1, characterized in that, it further includes: Setting initial conditions for the digital core model based on the hydrate decomposition conditions and the hydrate phase equilibrium curve, wherein the hydrate phase equilibrium curve is a curve for characterizing the change of temperature and pressure conditions required for the hydrate to maintain a solid state or decompose into a water and gas state, and the initial conditions include inlet water flow rate, inlet water temperature, wall temperature, initial temperature of the fluid domain, and initial pressure of the fluid domain.

3. The method according to claim 1, characterized in that, it further includes: Performing single-phase fluid seepage based on the digital core model and the transport mechanism model to determine initial flow field parameters, wherein the initial flow field parameters include flow field pressure, flow field temperature, and fluid velocity in the flow field.

4. The method according to claim 3, characterized in that, Determining the variation curve of the dynamic permeability of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the digital core model and the transport mechanism model, including: Determining the variation curve of the absolute permeability of the hydrate core and the variation curve of the dynamic permeability of the multiphase fluid at different hydrate saturations during the hydrate decomposition process in the core based on the initial flow field parameters, the digital core model, and the transport mechanism model, where the multiphase fluid includes water and methane.

5. A device for calculating the dynamic permeability of a hydrate core Characterized in that A determination unit for determining a digital core model based on a hydrate core, where the digital core model includes a hydrate part and a pore part; A second determination unit for determining a transport mechanism model for each phase fluid to pass through the hydrate part and the pore part based on the digital core model and the parameters of each phase fluid; A third determination unit for determining the variation curve of the dynamic permeability of the hydrate core at different hydrate saturations during the hydrate decomposition process in the core based on the digital core model and the transport mechanism model, where the saturation is a volume fraction; The determining the digital core model based on the hydrate core includes: Obtaining a CT image of the hydrate core based on CT scanning technology under the condition that the temperature and pressure ensure the stability of the hydrate in the core; Constructing an initial digital core model based on the CT image of the hydrate core; Adding flow field expansion regions to the inlet and outlet of the initial digital core model respectively to determine the digital core model; Wherein, the digital core model parameters include model size, model porosity, initial hydrate saturation, digital core grid number, and core permeability without hydrate; The determining the transport mechanism model for each phase fluid to pass through the hydrate part based on the digital core model and the parameters of each phase fluid includes: Determining the digital core model parameters and the parameters of each phase fluid, where the parameters of each phase fluid include fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity; Determining the transport mechanism model of the hydrate part based on the digital core model parameters and the parameters of each phase fluid through the enthalpy change equation, the CK equation, and the momentum source term; The determining the transport mechanism model for each phase fluid to pass through the pore part based on the digital core model and the parameters of each phase fluid includes: Determining the digital core model parameters and the parameters of each phase fluid, where the parameters of each phase fluid include fluid name, fluid density, fluid viscosity, fluid thermal conductivity, and fluid specific heat capacity; Determining the transport mechanism model of the pore part based on the digital core model parameters and the parameters of each phase fluid through the VOF model and the NS equation.

6. A computer-readable storage medium Characterized in that The computer-readable storage medium includes a stored program, where when the program is executed by a processor, the steps of the method for calculating the dynamic permeability of a hydrate core according to any one of claims 1 to 4 are implemented.

7. An electronic device Characterized in that The electronic device includes at least one processor and at least one memory connected to the processor; wherein, the processor is configured to call program instructions in the memory and execute the steps of the method for calculating the dynamic permeability of a hydrate core according to any one of claims 1 to 4.

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