A method and system for designing parameters of a natural gas hydrate exploitation experimental model

Abstract

The application discloses a design method of a natural gas hydrate exploitation experiment model parameter, and comprises the following steps: establishing a three-dimensional dynamic decomposition mathematical model of a natural gas hydrate reservoir by a mass conservation equation, an energy conservation equation, a definite solution condition and an auxiliary equation of each component of the natural gas hydrate reservoir; performing non-dimensionalization on the obtained three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir, and obtaining a plurality of similarity parameters; defining two characteristic times according to a flow control mechanism and a decomposition control mechanism of the natural gas hydrate reservoir exploitation, and then performing proportional modeling on the obtained similarity parameters; and designing the natural gas hydrate experiment model parameter according to the modeling result. The application can quantitatively connect the indoor experiment result with the mining practice.

Description

Technical Field

[0001] This invention relates to a model design method, and more particularly to a method and system for designing parameters of an experimental model for natural gas hydrate extraction based on similarity theory. Background Technology

[0002] Natural gas hydrate is an ice-like solid crystalline substance composed of natural gas and water molecules. Since natural gas is primarily composed of methane, it is also called methane hydrate. Due to its high methane content, it possesses extremely strong flammability and can be directly burned, hence its common name "combustible ice." Natural gas hydrate has a very high energy density; theoretical calculations show that 1 cubic meter of natural gas hydrate... 3 Saturated natural gas hydrates can release 164 m³ under standard conditions. 3 The methane gas produced by natural gas hydrates has an energy density 10 times that of other unconventional source rocks (such as coalbed methane and black shale), and 2 to 5 times that of conventional natural gas, equivalent to the energy of 0.164 tons of oil. Furthermore, the combustion of natural gas hydrates produces only carbon dioxide and water, without polluting the environment, making it a rare green and clean energy source. Most importantly, natural gas hydrate reserves are extremely abundant. Based on the analysis of stable conditions for the formation of natural gas hydrates, 20.7% of land and 90% of the ocean floor have favorable conditions for their formation. Based on this, it is estimated that the methane carbon content in global natural gas hydrates reaches 10... 16 kg or containing 20×10 15 m 3 The methane gas produced is equivalent to twice the total carbon reserves of all known conventional fossil fuels such as coal, oil, and natural gas in the world, and will become the most important energy source for mankind in the 21st century.

[0003] Compared to field experiments, physical simulations offer advantages such as lower cost, shorter time consumption, and ease of operation. With the deepening of theoretical research, laboratory experiments, and field practice on natural gas hydrates, the commercial exploitation of natural gas hydrates has gradually been put on the agenda. Currently, many researchers have conducted numerous laboratory experiments on the decomposition of natural gas hydrates, but these experiments are not based on the principle of similarity, resulting in the results not being directly applicable to guiding or predicting field operations. Therefore, conducting physical simulation experiments guided by similarity theory is essential for the field practice of natural gas hydrate exploitation. The theoretical basis of natural gas hydrate exploitation experimental models based on similarity theory is similarity theory itself, while similarity criteria guide model design and experimental operation. It can be used to study the seepage laws of fluids within hydrate reservoirs, investigate various exploitation mechanisms, and guide the design and optimization of natural gas hydrate exploitation schemes. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide a design method for experimental model parameters of natural gas hydrate extraction based on similarity theory. This design method can quantitatively link indoor experimental results with mining practices.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for designing parameters for an experimental model of natural gas hydrate extraction, comprising the following steps:

[0007] A three-dimensional dynamic decomposition mathematical model of a natural gas hydrate reservoir is established based on the mass conservation equation, energy conservation equation, boundary conditions, and auxiliary equations of each component.

[0008] The obtained three-dimensional dynamic decomposition mathematical model of natural gas hydrate reservoir was dimensionless to obtain multiple similarity criteria.

[0009] Based on the flow control mechanism and decomposition control mechanism of natural gas hydrate reservoir exploitation, two characteristic times are defined, and then the obtained similarity criteria are scaled up.

[0010] The experimental model parameters for natural gas hydrates were designed based on the modeling results.

[0011] The design method described above is characterized by dimensionless transformation of the obtained three-dimensional dynamic decomposition mathematical model of natural gas hydrate reservoirs to obtain multiple similarity criteria, specifically as follows:

[0012] Define a dimensionless variable;

[0013] Substituting dimensionless variables into the established three-dimensional dynamic decomposition mathematical model of natural gas hydrate reservoirs, we obtain the dimensionless form of the three-dimensional dynamic decomposition mathematical model of natural gas hydrate reservoirs.

[0014] Multiple similarity criteria were obtained through a dimensionless three-dimensional dynamic decomposition mathematical model of natural gas hydrate reservoirs.

[0015] The obtained similarity criteria are classified to obtain similarity criteria that guarantee similarity of fluid and porous media, similarity criteria that guarantee similarity of potential distribution, similarity criteria that guarantee similarity of temperature distribution, similarity criteria that guarantee similarity of phase permeability, similarity criteria that guarantee similarity of dynamic system, similarity criteria that guarantee similarity of geometry, and similarity criteria that guarantee similarity of time.

[0016] The design method, preferably, defines two characteristic times as follows: and Where τ1 represents the time taken for the water phase to flow through a porous medium of length L when driven by bottom hole pressure; τ2 represents the time required for complete decomposition of hydrates per unit volume of formation when driven by bottom hole pressure; L represents the length of the hydrate reservoir; ρ H Represents the density of the hydrate phase; μ A P represents the viscosity of the aqueous phase. gp Indicates the bottom pressure of the production well; k d φ0 represents the kinetic decomposition rate constant of the hydrate; k0 represents the absolute permeability of the formation after complete decomposition of the hydrate; φ0 represents the porosity of the formation after complete decomposition of the hydrate; k rrgA This represents the relative permeability of the water phase under residual gas conditions.

[0017] The design method, preferably, uses τ1 as the characteristic time when the natural gas hydrate reservoir is flow-controlled and τ2 as the characteristic time when the natural gas hydrate reservoir is decomposition-controlled.

[0018] For flow-controlled natural gas hydrate reservoirs, τ1 is substituted into the similarity criterion that guarantees time similarity for modeling.

[0019] For decomposition-controlled natural gas hydrate reservoirs, τ2 is substituted into the similarity criterion that guarantees time similarity for modeling.

[0020] The design method, preferably, involves designing the experimental model parameters for natural gas hydrates based on the modeling results as follows:

[0021] For actual natural gas hydrate reservoirs with flow control, when designing experimental models, the length, width, height, production well location, water injection well location, supply radius, and well radius of the experimental model are reduced based on the prototype using the same geometric scaling ratio. The same fluid, porous medium, pressure, and temperature are used as in the prototype. This ensures that during the production simulation, the production time in the experimental model is reduced by a geometric scaling ratio of 1 / 2, and the water injection rate, heat injection rate, liquid production rate, and gas production rate are reduced by a geometric scaling ratio of 1 / 2.

[0022] For actual natural gas hydrate reservoirs under decomposition control, when designing experimental models, the length, width, height, production well location, water injection well location, supply radius, and well radius of the experimental model are reduced based on the prototype using the same geometric scale. The same fluid pore medium, pressure, and temperature are used as in the prototype. This ensures that during production simulation, the absolute permeability of the formation in the experimental model is reduced by a geometric scale of 4 / 3 times compared to the prototype, the production time is reduced by a geometric scale of 2 / 3 times compared to the prototype, and the water injection rate, heat injection rate, liquid production rate, and gas production rate are reduced by a geometric scale of 7 / 3 times compared to the prototype.

[0023] Secondly, the present invention provides a design system for experimental model parameters of natural gas hydrate extraction, comprising:

[0024] The first processing unit is used to establish a three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir based on the mass conservation equation, energy conservation equation, boundary conditions, and auxiliary equations of each component of the natural gas hydrate reservoir.

[0025] The second processing unit is used to dimensionlessly transform the obtained three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir and obtain multiple similarity criteria.

[0026] The third processing unit is used to define two characteristic times based on the flow control mechanism and decomposition control mechanism of natural gas hydrate reservoir exploitation, and then scale the obtained similarity criteria.

[0027] The fourth processing unit is used to design experimental model parameters for natural gas hydrates based on the modeling results.

[0028] Thirdly, the present invention provides a computer storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the design method described in the first aspect of the present invention.

[0029] Fourthly, the present invention provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the design method described in the first aspect of the present invention.

[0030] The present invention has the following advantages due to the adoption of the above technical solutions:

[0031] 1. In this invention, when designing an experimental model for actual natural gas hydrate reservoirs with flow control, the length, width, height, production well location, water injection well location, supply radius, and well radius of the experimental model are reduced to the same geometric scale as the prototype. The same fluid, porous medium, pressure, and temperature are used as in the prototype. Thus, during the production simulation process, the production time in the experimental model is reduced by a geometric scale multiple of the prototype, and the water injection rate, heat injection rate, liquid production rate, and gas production rate are reduced by a geometric scale multiple of the prototype.

[0032] 2. In designing the experimental model for the actual natural gas hydrate reservoir under decomposition control, the length, width, height, production well location, water injection well location, supply radius, and well radius of the experimental model are reduced to the same geometric scale as the prototype. The same fluid, porous medium, pressure, and temperature are used as in the prototype. Thus, during the production simulation, the absolute permeability of the formation in the experimental model is reduced by a geometric scale of 4 / 3 times compared to the prototype, the production time is reduced by a geometric scale of 2 / 3 times compared to the prototype, and the water injection rate, heat injection rate, liquid production rate, and gas production rate are reduced by a geometric scale of 7 / 3 times compared to the prototype. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "setting," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] The following is a detailed description of the design method and system for the experimental model parameters of natural gas hydrates provided in the embodiments of the present invention.

[0036] Example 1:

[0037] This invention provides a method for designing experimental model parameters for natural gas hydrates, comprising the following steps:

[0038] S100. A three-dimensional mathematical model of natural gas hydrate reservoir is established based on the mass conservation equation, energy conservation equation, initial conditions, boundary conditions, and auxiliary equations of each component of the natural gas hydrate reservoir.

[0039] Currently, there are two models to describe the decomposition of natural gas hydrates—the kinetic model and the equilibrium model. Studies have shown that the kinetic model is more accurate; therefore, this embodiment adopts the kinetic model. In the kinetic model, the relationship between phases and components is shown in Table 1:

[0040] Table 1. Relationship between phases and components in the kinetic model.

[0041]

[0042]

[0043] In Table 1: β≡H represents the hydrate phase; β≡A represents the aqueous phase; β≡G represents the gas phase; β≡I represents the ice phase; k≡h represents the hydrate component; k≡w represents the water component; k≡m represents the methane component; k≡i represents the inhibitor component.

[0044] The mass conservation equation and the energy conservation equation can be expressed by the following formulas:

[0045]

[0046] In the formula, V,V n M represents the volume and the volume of subfield n, respectively; k Γ,Γ represents the cumulative mass term of component k; n Let F represent the surface area and the surface area of ​​subdomain n, respectively; k The Darcy flow vector represents the component; n represents the inward unit normal vector; q k The term represents the source / sink of the component; t represents time. The left side of the equal sign represents the cumulative term, the first term on the right side represents the flow term, and the second term on the right side represents the source / sink term.

[0047] Among them, the cumulative quality term:

[0048]

[0049] The contribution of the flow term comes from the gas phase and the aqueous phase:

[0050]

[0051] in,

[0052] Quality accumulation item:

[0053]

[0054] in,

[0055] Energy accumulation term:

[0056]

[0057] Energy flow term:

[0058]

[0059] Energy source sink:

[0060]

[0061] Based on the above explanation, the following energy conservation equation and mass conservation equation for each component can be obtained.

[0062] Water component mass conservation equation:

[0063]

[0064] In the formula, t represents time; S A S represents the water phase saturation. G Indicates gas phase saturation; S I Indicates ice phase saturation; SH Indicates the saturation of the hydrate phase; ρ A ρ represents the density of the aqueous phase. G ρ represents the gas phase density. I ρ represents the density of the ice phase; H Indicates the density of the hydrate phase; This indicates the mass fraction of water in the aqueous phase; Indicates the mass fraction of water in the gas phase; k rA k represents the relative permeability of the aqueous phase. rG μ represents the relative permeability of the gas phase. A μ represents the viscosity of the aqueous phase. G P represents the viscosity of the gas phase. A P represents the pressure in the aqueous phase. G b represents the gas phase pressure; b represents the slip factor; P gp Indicates the bottom pressure of the production well; q I Indicates the water injection rate; L, W, H represent the length, width, and height of the hydrate reservoir; R e ,R w Represents the supply radius and well radius; x, y, z represent geometric coordinates; x p ,y p The coordinates of the production well; x I ,y I The coordinates of the injection well are represented by g; g represents the acceleration due to gravity; P eq Indicates the equilibrium pressure of the hydrate phase; N represents the hydrate index; W w k represents the molar mass of water. d This represents the rate constant for the kinetic decomposition of hydrates.

[0065] The mass conservation equation for methane components:

[0066]

[0067] In the formula, This indicates the mass fraction of methane in the aqueous phase; W represents the mass fraction of methane in the gas phase. m This indicates the molar mass of methane.

[0068] Mass conservation equation for inhibitor components:

[0069]

[0070] In the formula, ρ R Indicates rock density; This represents the adsorption partition coefficient.

[0071] Mass conservation equation for hydrate components:

[0072]

[0073] Energy conservation equation:

[0074]

[0075] In the formula, C R T represents the specific heat of the rock; T represents the temperature of the hydrate reservoir; u w This represents the specific internal energy of water in the aqueous phase; u m This represents the specific internal energy of methane in the aqueous phase. This indicates the specific internal energy related to methane dissolution; This indicates the specific internal energy related to inhibitor dissolution; This represents the specific internal energy of water in the gas phase. U represents the specific internal energy of methane in the gas phase; dep This represents the specific internal energy leaving the gas phase; u I This represents the specific internal energy of ice; u H ΔH represents the specific internal energy of a hydrate. f K represents the heat of melting ice; R K represents the thermal conductivity of rock. H K represents the thermal conductivity of the hydrate phase. I K represents the thermal conductivity of the ice phase. A K represents the thermal conductivity of the aqueous phase. G μ represents the thermal conductivity of the gas phase. G hw represents the viscosity of the gas phase; hw represents the specific enthalpy of water in the aqueous phase. μ represents the specific enthalpy of methane in the gas phase. A H represents the viscosity of the aqueous phase. dep Indicates the specific enthalpy produced upon leaving the gas phase; H m This indicates the specific enthalpy of methane in the aqueous phase; This indicates the specific enthalpy produced when methane dissolves in water; q represents the specific enthalpy generated when the inhibitor dissolves in the aqueous phase; d Indicates the heat injection rate; ΔH 0 This indicates the heat of decomposition of hydrates.

[0076] Initial conditions:

[0077] p| t＝0 =p i ,T| t＝0 =T i , (S A ) t＝0 =S Ai ,(S G ) t＝0 =S Gi ,(S H ) t＝0 =S Hi

[0078]

[0079] In the formula, p i T represents the initial pressure of the hydrate reservoir. i Indicates the initial temperature of the hydrate reservoir; S Ai S represents the initial water phase saturation. Gi S represents the initial gas phase saturation. Hi Indicates the initial hydrate saturation; This indicates the mass fraction of the inhibitor in the aqueous phase under initial conditions; This indicates the mass fraction of water in the gas phase under initial conditions; This indicates the mass fraction of methane in the aqueous phase under initial conditions.

[0080] Boundary conditions include:

[0081] External boundary conditions:

[0082]

[0083] Boundary conditions within the production well:

[0084] P = P gp T = T gp

[0085] Injection well boundary conditions:

[0086] q = q I T = T I

[0087] In the formula, This indicates the mass fraction of methane in the aqueous phase under reference conditions. ρ represents the mass fraction of water in the gas phase under reference conditions. G0 c represents the gas phase density under reference conditions. A c represents the compressibility coefficient of the aqueous phase. φ φ represents the rock compressibility coefficient; k0 represents the absolute permeability of the formation after complete hydrate decomposition; φ0 represents the formation porosity after complete hydrate decomposition; σ represents the interfacial tension; p A0 Indicates reference pressure; S Gr S represents residual gas saturation. Ac The bound water saturation is represented by z0; the gas compressibility factor under reference conditions is represented by z0; J represents the Leverett function; θ represents the wetting angle; p c T represents capillary force; T0 represents the reference temperature; T gp Indicates the bottom hole temperature; T f Indicates the freezing point of salt water; T I Indicates the temperature of the injected water; T H T represents the phase equilibrium temperature in pure water. sThis indicates the phase equilibrium temperature in the brine.

[0088] Saturation equation:

[0089] S H +S A +S I +S G =1

[0090] Mass fraction equations for gas and water phases:

[0091]

[0092] Capillary force equation:

[0093]

[0094] Aqueous phase state equation:

[0095] ρ A =ρ A0 [1+c A (P A -P A0 )]

[0096] Gas phase equation of state:

[0097]

[0098] Rock state equation:

[0099]

[0100] Effective porosity equation:

[0101] φ e =φ(1-S H -S I )

[0102] Permeability change equation:

[0103] k=k0(1-S H -S I ) n

[0104] Equation on the effect of inhibitors on hydrate phase equilibrium temperature:

[0105]

[0106] In the above formulas, x, y, z represent geometric coordinates in meters (m); L, W, H represent the length, width, and height of the hydrate reservoir, respectively; x p ,y p The coordinates of the production well; x I ,y IThe coordinates of the injection well are represented by t; time is represented by t. This indicates the mass fraction of water in the gas phase under reference conditions. This indicates the mass fraction of the inhibitor in the aqueous phase under initial conditions; This indicates the mass fraction of water in the gas phase under initial conditions; R represents the mass fraction of methane in the aqueous phase under initial conditions. e ,R w Indicates the supply radius and well radius; Indicates the mass fraction of methane in the aqueous phase under reference conditions; u m Indicates the specific internal energy of methane in the aqueous phase; u w This represents the specific internal energy of water in the aqueous phase. This indicates the specific internal energy related to methane dissolution; This indicates the specific internal energy related to inhibitor dissolution; This represents the specific internal energy of water in the gas phase. U represents the specific internal energy of methane in the gas phase; dep ρ represents the specific internal energy leaving the gas phase. G0 ρ represents the gas phase density under reference conditions. H ρ represents the density of hydrates. I ρ represents the density of ice. R c represents the density of the rock. A Indicates the compressibility coefficient of the aqueous phase; u I This represents the specific internal energy of ice; u H h represents the specific internal energy of a hydrate. w This indicates the specific enthalpy of water in the aqueous phase. H represents the specific enthalpy of methane in the gas phase; dep Indicates the specific enthalpy produced upon leaving the gas phase; c φ H represents the rock compressibility coefficient; m Indicates the specific enthalpy of methane in the aqueous phase; k0 represents the specific enthalpy produced by the dissolution of methane in water; k0 represents the absolute permeability of the formation after the complete decomposition of the hydrate, in μm. 2 ;k rG Represents the relative permeability of the gas phase, 1; k rA Indicates the relative permeability of the aqueous phase; C represents the specific enthalpy generated when the inhibitor dissolves in the aqueous phase. R K represents the specific heat of rocks. A φ0 represents the thermal conductivity of the aqueous phase; K represents the formation porosity after complete decomposition of the hydrate. G μ represents the thermal conductivity of the gas phase. G Indicates gas phase viscosity; μ A Indicates the viscosity of the aqueous phase; K H K represents the thermal conductivity of hydrates. R σ represents the thermal conductivity of the rock; b represents the interfacial tension; p represents the slip factor.A0 p represents the reference pressure. i p represents the initial pressure of the hydrate reservoir. gp p represents the bottom pressure of the production well. eq S represents the equilibrium pressure of the hydrate phase. Gr S represents residual gas saturation. Ac S indicates the degree of bound water saturation. Hi S represents the initial hydrate saturation. Gi The initial gas phase saturation is represented by z; z0 represents the gas compressibility factor under reference conditions; J represents the Leverett function; g represents gravitational acceleration; θ represents the wetting angle; p A p represents the pressure in the water phase. G p represents the gas phase pressure. c Indicates capillary force; N represents the hydrate index; K represents capillary force. I Indicates the thermal conductivity of the ice phase; Indicates the adsorption partition coefficient; T0 represents the reference temperature; T gp Indicates the bottom hole temperature; T i Indicates the initial temperature of the hydrate reservoir; ΔH 0 Indicates the heat of decomposition of hydrates; ΔH f Indicates the heat of ice melting; q I Indicates the water injection rate; q d Indicates the heat injection rate; T f Indicates the freezing point of salt water; This indicates the mass fraction of methane in the aqueous phase; This indicates the mass fraction of water in the aqueous phase; S represents the mass fraction of water in the gas phase. A S represents the water phase saturation. G Indicates gas phase saturation; S H Indicates the hydrate phase saturation; T represents the hydrate reservoir temperature; W w W represents the molar mass of water. m S represents the molar mass of methane; Ai T represents the initial water phase saturation; I Indicates the temperature of the injected water; T H K represents the phase equilibrium temperature in pure water. d S represents the rate constant for the kinetic decomposition of hydrates. I Indicates ice phase saturation; T s This indicates the phase equilibrium temperature in the brine.

[0107] S200. The obtained three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir is dimensionless to obtain multiple similarity criteria, specifically:

[0108] S201. Define a dimensionless variable:

[0109] Dimensionless independent variable:

[0110]

[0111] Where τ is the characteristic time;

[0112] Dimensionless dependent variable:

[0113]

[0114]

[0115] Where Δs=1-S Ac -S Gr ;

[0116]

[0117] Where k rcwG k represents the relative permeability of the gas phase under bound water conditions. rrgA This represents the relative permeability of the aqueous phase under residual gas conditions.

[0118] Dimensionless parameter:

[0119]

[0120] S202. Substituting dimensionless variables into the established three-dimensional dynamic decomposition mathematical model of natural gas hydrate reservoirs, we obtain the dimensionless form of the three-dimensional dynamic decomposition mathematical model of natural gas hydrate reservoirs:

[0121] Dimensionless form of the water component mass conservation equation:

[0122]

[0123] Dimensionless form of the mass conservation equation for methane components:

[0124]

[0125]

[0126] Dimensionless form of the mass conservation equation for inhibitor components:

[0127]

[0128] Dimensionless form of the mass conservation equation for hydrate components:

[0129]

[0130] Dimensionless form of the energy conservation equation:

[0131]

[0132]

[0133] Dimensionless form of the initial conditions:

[0134]

[0135]

[0136] Dimensionless form of outer boundary conditions:

[0137] Dimensionless form of the boundary conditions for production wells β=A,G,l=L,W,H:

[0138]

[0139] Dimensionless form of the injection well boundary conditions:

[0140]

[0141] The dimensionless form of the saturation equation:

[0142]

[0143] Dimensionless form of the mass fraction equations for the aqueous and gas phases:

[0144]

[0145] Dimensionless form of the capillary force equation:

[0146]

[0147] Dimensionless form of the equation of state for the aqueous phase:

[0148]

[0149] Dimensionless form of the gas phase equation of state:

[0150] Depend on have to Dimensionless form of the rock state equation:

[0151]

[0152] Dimensionless form of the effective porosity equation:

[0153]

[0154] Permeability change equation:

[0155]

[0156] Equation on the effect of inhibitors on hydrate phase equilibrium temperature:

[0157]

[0158] S203. The following 70 similarity criteria can be obtained through a dimensionless three-dimensional dynamic decomposition mathematical model of natural gas hydrate reservoirs:

[0159] π1=S Gr ,π2=S Ac ,π3=S Hi ,π4=S Ai ,π5=S Gi , π 38 =φ0, π 49 =c A p gp ,π 50 =c φ p gp , π 52 =z0,

[0160] Natural gas hydrate extraction involves 77 parameters, including four fundamental dimensions: length, time, mass, and temperature. According to the π-theorem, there should be 77 - 4 = 73 π terms. These can be supplemented using dimensional analysis.

[0161] π 71 =θ,π 72 =J,

[0162] Classify the above similarity criteria:

[0163] Similarity criteria that ensure the similarity of fluids and porous media:

[0164] π 38 =φ0,π 49 =c A p gp ,π 50 =c φ p gp ,π 52 =z0, π 71=θ,π 72 =J;

[0165] Similarity criteria that ensure similar potential distributions:

[0166]

[0167] Similarity criteria that ensure similar temperature distributions:

[0168]

[0169] Similarity criterion to ensure reactivity:

[0170] π1=S Gr ,π2=S Ac ,π3=S Hi ,π4=S Ai ,π5=S Gi ,

[0171] Similarity criteria that ensure the similarity of dynamic systems:

[0172]

[0173] Similarity criteria that guarantee geometric similarity:

[0174]

[0175] Similarity criteria that guarantee temporal similarity:

[0176]

[0177] S300. There are two control mechanisms for the exploitation of natural gas hydrate reservoirs: flow control and decomposition control. When a natural gas hydrate reservoir is flow-controlled, it indicates that the seepage resistance is relatively high, and the exploitation effect is controlled by the flow capacity of the fluid within the reservoir. When a natural gas hydrate reservoir is decomposition-controlled, it indicates that the seepage resistance is relatively low, and the exploitation effect is determined by the rate of natural gas hydrate decomposition. Based on these two control mechanisms, two characteristic times are defined. and Where τ1 represents the time taken for the water phase to flow through a porous medium of length L when driven by bottom hole pressure, and τ2 represents the time required for the complete decomposition of natural gas hydrates per unit volume of formation when driven by bottom hole pressure. When the natural gas hydrate reservoir is flow-controlled, τ1 is used as the characteristic time; when the natural gas hydrate reservoir is decomposition-controlled, τ2 is used as the characteristic time.

[0178] (1) For flow-controlled natural gas hydrate reservoirs, τ1 is substituted into the similarity criterion for guaranteed time similarity for modeling:

[0179] The fluid, pore medium, temperature, and pressure in the three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir are made identical to those in the mine, and the physical quantities related to geometric dimensions are scaled down to the same geometric ratio. The modeling result is: r(W) = r(H) = r(R) e )=r(R w )=r(x p )=r(y p )=r(x I )=r(y I )=r(L),r(τ)=r(L 2 ), r(q I )=r(q d ) = r(L), and the other parameters are scaled down to 1;

[0180] (2) For decomposition-controlled natural gas hydrate reservoirs, τ2 is substituted into the similarity criterion for ensuring time similarity for modeling:

[0181] Using the same modeling method as the flow control mechanism, the modeling result is: r(W) = r(H) = r(R) e )=r(R w )=r(x p )=r(y p )=r(x I )=r(y I )=r(L), The scale of other parameters is 1.

[0182] S400. Design the experimental model parameters for natural gas hydrates based on the modeling results of step S300:

[0183] (1) For actual natural gas hydrate reservoirs with flow control, when designing experimental models, the length, width, height, production well location, water injection well location, supply radius and well radius of the experimental model are reduced based on the prototype using the same geometric scaling ratio. The same fluid, porous medium, pressure and temperature are used as in the prototype. In this way, during the production simulation process, the production time in the experimental model is reduced by a geometric scaling ratio of 1 / 2, and the water injection rate, heat injection rate and liquid production rate and gas production rate are reduced by a geometric scaling ratio of 1 / 2 (see Table 2 below).

[0184] Table 2. Parameter design of the experimental model for flow-controlled hydrate reservoirs (geometric scale 1:200)

[0185] physical quantity prototype value Model values <![CDATA[k0,μm 2 ]]> 3.0 0.00256 <![CDATA[q I ,m 3 / s]]> 5e-3 2.14e-8 <![CDATA[q d ,J / s]]> 5000 0.0128 t 10 days 7.02 hours

[0186] (2) For the actual natural gas hydrate reservoirs under decomposition control, when designing the experimental model, the length, width, height, production well location, water injection well location, supply radius and well radius of the experimental model are reduced by the same geometric scale based on the prototype. The same fluid, porous medium, pressure and temperature are used as in the prototype. In this way, during the production simulation, the absolute permeability of the formation in the experimental model is reduced by 4 / 3 times the geometric scale of the prototype, the production time is reduced by 2 / 3 times the geometric scale of the prototype, and the water injection rate, heat injection rate and liquid production rate and gas production rate are reduced by 7 / 3 times the geometric scale of the prototype (see Table 3 below).

[0187] Table 3. Parameter design of the experimental model for decomposition control of hydrate reservoirs (geometric scale 1:200)

[0188] physical quantity prototype value Model values <![CDATA[q I ,m 3 / s]]> 5e-3 2.5e-5 <![CDATA[q d ,J / s]]> 5000 25 t 100 days 3.6 minutes

[0189] Example 2:

[0190] The above-described embodiment 1 provides a method for designing experimental model parameters for natural gas hydrate extraction. Correspondingly, this embodiment provides a system for designing experimental model parameters for natural gas hydrate extraction. The system provided in this embodiment can implement the method for designing experimental model parameters for natural gas hydrate extraction in embodiment 1. This system can be implemented through software, hardware, or a combination of both. For example, the system may include integrated or separate functional modules or units to execute the corresponding steps in the methods of embodiment 1. Since the system for designing experimental model parameters for natural gas hydrate extraction in this embodiment is basically similar to the method embodiment, the description process in this embodiment is relatively simple. For relevant details, please refer to the description in embodiment 1. The system for designing experimental model parameters for natural gas hydrate extraction in this embodiment is merely illustrative.

[0191] This embodiment provides a design system for the experimental model parameters of natural gas hydrate extraction, which includes:

[0192] The first processing unit is used to establish a three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir based on the mass conservation equation, energy conservation equation, boundary conditions, and auxiliary equations of each component of the natural gas hydrate reservoir.

[0193] The second processing unit is used to dimensionlessly transform the obtained three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir and obtain multiple similarity criteria.

[0194] The third processing unit is used to define two characteristic times based on the flow control mechanism and decomposition control mechanism of natural gas hydrate reservoir exploitation, and then scale the obtained similarity criteria.

[0195] The fourth processing unit is used to design experimental model parameters for natural gas hydrates based on the modeling results.

[0196] Example 3:

[0197] This embodiment provides a processing device for implementing the design method of the experimental model parameters for natural gas hydrate extraction provided in Embodiment 1. The processing device can be a client-side processing device, such as a mobile phone, laptop, tablet computer, desktop computer, etc., to execute the design method of Embodiment 1.

[0198] The processing device includes a processor, a memory, a communication interface, and a bus. The processor, memory, and communication interface are connected via the bus to enable communication between them. The memory stores a computer program that can run on the processor. When the processor runs the computer program, it executes the design method for the experimental model parameters of natural gas hydrate extraction provided in Embodiment 1.

[0199] Preferably, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0200] Preferably, the processor can be any type of general-purpose processor such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation herein.

[0201] Example 4:

[0202] The method for designing the experimental model parameters for natural gas hydrate extraction in Embodiment 1 can be specifically implemented as a computer program product. The computer program product may include a computer-readable storage medium on which computer-readable program instructions for executing the design method described in Embodiment 1 are loaded.

[0203] A computer-readable storage medium can be a tangible device that holds and stores instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof.

[0204] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing parameters of a natural gas hydrate production experiment model, characterized in that, The method comprises the following steps: a three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir is established according to the mass conservation equation, the energy conservation equation, the definite solution condition and the auxiliary equation of each component of the natural gas hydrate reservoir; dimensionless processing is performed on the obtained three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir, and a plurality of similarity criteria are obtained; two characteristic times are defined according to the flow control mechanism and the decomposition control mechanism of the natural gas hydrate reservoir exploitation, and then the obtained similarity criteria are proportionally modeled; the experimental model parameters of the natural gas hydrate are designed according to the modeling results; The two defined characteristic times are respectively and ,in This indicates the flow of water phase when driven by bottom hole pressure. The time taken for long porous media; This represents the time required for complete decomposition of hydrates per unit volume of formation when bottomhole pressure is the driving force. Indicates the length of hydrate reservoirs; Indicates the density of the hydrate phase; Indicates the viscosity of the aqueous phase; Indicates the bottom pressure of the production well; This represents the rate constant for the kinetic decomposition of hydrates; This represents the absolute permeability of the formation after the complete decomposition of hydrates. This indicates the formation porosity after the complete decomposition of hydrates. This represents the relative permeability of the water phase under residual gas conditions.

2. The design method of claim 1, wherein dimensionless processing is performed on the obtained three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir, and a plurality of similarity criteria are obtained, specifically as follows: dimensionless variables are defined; the dimensionless variables are brought into the established three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir, and a dimensionless form of the three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir is obtained; a plurality of similarity criteria are obtained through the dimensionless form of the three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir; the obtained similarity criteria are classified, and the similarity criteria ensuring the similarity of the fluid and the pore medium, the similarity criteria ensuring the similarity of the potential distribution, the similarity criteria ensuring the similarity of the temperature distribution, the similarity criteria ensuring the similarity of the relative permeability, the similarity criteria ensuring the similarity of the dynamic system, the similarity criteria ensuring the similarity of the geometry and the similarity criteria ensuring the similarity of the time are obtained.

3. The design method of claim 2, wherein When the natural gas hydrate reservoir is flow controlled, the following is used is the characteristic time; When the natural gas hydrate reservoir is under dissociation control, the following methods are used The characteristic time is: For flow control of natural gas hydrate reservoirs, one can Bringing into the similar dimensionless numbers that guarantee the similarity of time, the model is made; For a dissociation-controlled gas hydrate reservoir, the following equation is used The similarity criterion is introduced into the similarity time, and the model is established.

4. The method of designing according to claim 3, wherein, The experimental model parameters of the natural gas hydrate are designed according to the modeling results, specifically as follows: for the actual natural gas hydrate reservoir of the flow control, when the experimental model is designed, the length, the width, the height, the production well position, the water injection well position, the supply radius and the well radius of the experimental model are reduced by the same geometric scaling ratio on the basis of the prototype, and the same fluid, the pore medium, the pressure and the temperature as the prototype are adopted, so that in the production simulation process, the production time of the experimental model is reduced by the square of the geometric scaling ratio of the prototype, and the water injection rate, the heat injection rate and the liquid and gas production rate are reduced by the geometric scaling ratio of the prototype; for the actual natural gas hydrate reservoir of the decomposition control, when the experimental model is designed, the length, the width, the height, the production well position, the water injection well position, the supply radius and the well radius of the experimental model are reduced by the same geometric scaling ratio on the basis of the prototype, and the same fluid, the pore medium, the pressure and the temperature as the prototype are adopted, so that in the production simulation process, the formation absolute permeability of the experimental model is reduced by the 4 / 3 power of the geometric scaling ratio of the prototype, the production time is reduced by the 2 / 3 power of the geometric scaling ratio of the prototype, and the water injection rate, the heat injection rate and the liquid and gas production rate are reduced by the 7 / 3 power of the geometric scaling ratio of the prototype.

5. A system for designing parameters of a natural gas hydrate production experiment model, characterized by, It comprises: a first processing unit for establishing a three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir according to the mass conservation equation, the energy conservation equation, the definite solution condition and the auxiliary equation of each component of the natural gas hydrate reservoir; a second processing unit for performing dimensionless processing on the obtained three-dimensional dynamic decomposition mathematical model of the natural gas hydrate reservoir, and obtaining a plurality of similarity criteria; a third processing unit for defining two characteristic times according to the flow control mechanism and the decomposition control mechanism of the natural gas hydrate reservoir exploitation, and then proportionally modeling the obtained similarity criteria; A fourth processing unit is configured to design the experimental model parameters of the natural gas hydrate according to the modeling result. The two defined characteristic times are respectively and ,in This indicates the flow of water phase when driven by bottom hole pressure. The time taken for long porous media; This represents the time required for complete decomposition of hydrates per unit volume of formation when bottomhole pressure is the driving force. Indicates the length of hydrate reservoirs; Indicates the density of the hydrate phase; Indicates the viscosity of the aqueous phase; Indicates the bottom pressure of the production well; This represents the rate constant for the kinetic decomposition of hydrates; This represents the absolute permeability of the formation after the complete decomposition of hydrates. This indicates the formation porosity after the complete decomposition of hydrates. This represents the relative permeability of the water phase under residual gas conditions.

6. A computer storage medium having stored thereon a computer program, characterized in that The computer program, when executed by a processor, implements the steps of the design method of any one of claims 1-4.

7. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor, when executing the computer program, implements the steps of the design method of any one of claims 1-4.

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