Method, device, medium and equipment for numerical simulation of foam oil in heavy oil reservoir

Abstract

The present invention relates to a method, device, medium and equipment for numerical simulation of foam oil in heavy oil reservoirs. The method comprises: setting assumptions based on foam oil, one of which is that foam oil is a pseudo-single phase; setting fluid motion equations of foam oil and continuous gas; setting a calculation method for physical property parameters of foam oil; setting a time-varying dynamic mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas; establishing a two-phase four-component seepage mathematical model of foam oil; giving initial conditions and boundary conditions of heavy oil reservoirs, and discretizing the two-phase four-component seepage mathematical model; performing full implicit solution on the discrete two-phase four-component seepage mathematical model to obtain the distribution of unknown quantities in each grid in the heavy oil reservoir and the well production. The method is more in line with the actual seepage situation of foam oil in heavy oil reservoirs, and provides a new theoretical basis for numerical simulation of foam oil in heavy oil reservoirs.

Description

Technical Field

[0001] The invention relates to a method, a device, a medium and equipment for numerical simulation of foam oil in a heavy oil reservoir, and belongs to the technical field of oil and gas exploitation. Background Art

[0002] As a solvent-based non-thermal recovery method, solvent huff and puff has shown great potential in some thin-layer heavy oil reservoirs. A solvent huff and puff cycle consists of three stages. First, a volatile solvent (such as methane, propane, etc.) is injected into the heavy oil reservoir. Then, the well is shut down to allow the solvent gas to dissolve into the crude oil, thereby reducing viscosity, swelling the oil, and reducing interfacial tension. Finally, the well is reopened for production. Due to the high viscous resistance of heavy oil, the dissolved gas will not aggregate immediately after release, but will exist in the oil as dispersed bubbles. This phenomenon is called foamy oil, which is an important mechanism of heavy oil dissolved gas drive and solvent huff and puff.

[0003] In terms of mathematical models of foam oil, commonly used models include pseudo-bubble point model and kinetic model. The pseudo-bubble point model still has limitations: it cannot describe the time-varying characteristics of foam oil; the addition of pseudo-bubble point increases the uncertainty of simulation. Taking oil and gas two-phase seepage as an example, in the pseudo-bubble point model, the bubble point pressure is the same as the black oil model. The relationship between the change of bubble point pressure and pressure is well known, but the change of pseudo-bubble point pressure with pressure is not clear. The kinetic model uses a series of pseudo-kinetic reactions and a fixed reaction rate constant to describe gas exchange. However, in the actual development of oil reservoirs, the seepage conditions from the bottom of the well to the deep part of the reservoir vary greatly, and the drastic changes in the parameter field caused by this will aggravate the heterogeneity of gas release. Even if the seepage conditions are not considered, the results of constant component expansion experiments of oil samples with different viscosities and different dissolved gas contents are not the same. The parameters adjusted to obtain a better fitting effect are unreasonable and difficult to explain. In addition, in solvent throughput, the concentration field is generally very drastic and cannot be ignored.

[0004] Therefore, it is necessary to establish a new time-varying numerical simulation method that takes into account the solvent mass transfer behavior and the dynamic exchange between solvent and gas. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a method, device, medium and equipment for numerical simulation of foam oil in heavy oil reservoirs. The method is a four-component time-varying numerical simulation method based on considering solvent mass transfer and dynamic exchange between solvent and gas. The constructed mathematical model takes into account the dynamic characteristics of gas exchange, including the influence of heavy oil viscosity on dissolved gas release, and the influence of heavy oil viscosity and dispersed bubble content on dispersed bubble aggregation. Finally, a fully implicit solution is performed by combining the finite difference method and Newton-Raphson iteration.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for numerical simulation of foamy oil in a heavy oil reservoir, comprising:

[0008] Based on foamy oil, the assumptions are as follows: foamy oil is a pseudo-single phase, containing three components: degassed oil, dissolved gas and dispersed bubbles, where the mixture of degassed oil and dissolved gas is diluent oil, and the flow rate of dispersed bubbles in foamy oil is the same as that of diluent oil; dispersed bubbles gather to form continuous gas, at which time the fluid is divided into two phases: foamy oil and continuous gas, ignoring the interfacial tension between diluent oil and dispersed bubbles in foamy oil, and ignoring the interfacial tension between foamy oil and continuous gas; ignoring rock compressibility, and assuming that the fluid obeys constant temperature Darcy flow;

[0009] Set the fluid motion equations for foamy oil and continuous gas;

[0010] Set the calculation method of the physical property parameters of foam oil;

[0011] Set the time-varying dynamic mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas;

[0012] Based on the set fluid motion equation, physical property parameter calculation method, and the mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas, a two-phase four-component seepage mathematical model of foamy oil is established.

[0013] Given the initial and boundary conditions of heavy oil reservoir, a two-phase four-component flow mathematical model is discretized;

[0014] The discrete two-phase four-component seepage mathematical model is solved implicitly to obtain the unknown quantity distribution of each grid in the heavy oil reservoir and the well production.

[0015] The method for numerical simulation of foamy oil in heavy oil reservoirs preferably sets the fluid motion equation as follows:

[0016] The motion equations of foamy oil and continuous gas obey Darcy's law:

[0017]

[0018]

[0019] Where p is the pressure variable; ρ fo , fg is the density of foam oil and continuous gas; H is the depth; g is the acceleration of gravity; v fo 、v fg are the seepage velocities of foam oil and continuous gas respectively; μ fo , μ fg are the viscosities of foam oil and continuous gas respectively; K rfo , K rfgare the relative permeabilities of foam oil and continuous gas, respectively; K is the absolute permeability; is the Hamiltonian operator.

[0020] The method for numerical simulation of foamy oil in heavy oil reservoirs preferably sets a method for calculating the physical property parameters of foamy oil, specifically as follows:

[0021] The density of foamy oil is determined by the density and mass fraction of degassed oil, dissolved gas, and dispersed bubbles:

[0022]

[0023] In the formula, x do 、x sg 、x dg are the mass fractions of degassed oil, dissolved gas and dispersed bubbles respectively; ρ do , sg , dg are the densities of degassed oil, dissolved gas, and dispersed bubbles, respectively;

[0024] The dispersed bubble density is calculated according to the gas state equation, and the degassed oil density and dissolved gas density are determined by their isothermal compression coefficients:

[0025]

[0026]

[0027] Where r represents the reference state; C do , C sg are the isothermal compressibility coefficients of degassed oil and dissolved gas, respectively.

[0028] The method for numerical simulation of foamy oil in heavy oil reservoirs preferably sets the time-varying dynamic mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles agglomerating to form continuous gas, specifically as follows:

[0029] R sg→dg =F sg→dg φs fo f o c sup M sg ×10 -3

[0030] R dg→fg =F dg→fg φs fo f dg ρ dg

[0031] In the formula, R sg→dg and R dg→fg represent the mass transfer rate from dissolved gas to dispersed bubbles and from dispersed bubbles to continuous gas respectively; F sg→dgand F dg→fg is the reaction rate constant; c sup is the supersaturation concentration; f o and f dg are the volume fractions of diluent oil and dispersed bubbles in foam oil, respectively; φ is the porosity; M sg is the molar mass of dissolved gas; s fo is the foam oil saturation;

[0032] The smaller the viscosity of the diluent oil, the larger the diffusion coefficient, and the faster the transformation and growth of the bubbles. sg→dg is a function of the diluent oil viscosity:

[0033]

[0034] The low viscosity diluent oil has a smaller viscosity force on the dispersed bubbles and a poorer binding ability, so the dispersed bubbles are more likely to coalesce. In addition, when the volume fraction of the dispersed bubbles is small, it is not easy to coalesce. Therefore, F dg→fg is a function of the dilution oil viscosity and the dispersed bubble volume fraction:

[0035]

[0036] In the formula, F sg→dg_base and F dg→fg_base is the cardinality term of the reaction rate constant; μ do is the viscosity of degassed oil; μ o is the viscosity of the diluent oil; f dg is the volume fraction of dispersed bubbles in foamy oil; m and n represent the correlation degree.

[0037] The method for numerical simulation of foam oil in heavy oil reservoirs preferably establishes a four-component seepage mathematical model of foam oil, which is specifically as follows:

[0038] According to the law of mass conservation, the two-phase four-component continuity equation is derived:

[0039] Deaerated oil:

[0040]

[0041] Dissolved gas:

[0042]

[0043] Dispersed bubbles:

[0044]

[0045] Continuous gas:

[0046]

[0047] In the formula, q fo,q fg are the outlet outputs of foam oil and continuous gas, respectively; D is the diffusion coefficient of dissolved gas in the diluent oil; c is the mass concentration of dissolved gas in the diluent oil; s fg is the continuous gas saturation.

[0048] A second aspect of the present invention provides a heavy oil reservoir foam oil numerical simulation device, comprising:

[0049] The first processing unit is used to set assumptions based on foam oil. The assumptions are as follows: foam oil is a pseudo-single phase and contains three components: degassed oil, dissolved gas and dispersed bubbles, wherein the mixture of degassed oil and dissolved gas is diluent oil, and the flow rate of dispersed bubbles in foam oil is the same as that of diluent oil; dispersed bubbles gather and form continuous gas, at which time the fluid is divided into two phases: foam oil and continuous gas, and the interfacial tension between diluent oil and dispersed bubbles in foam oil and the interfacial tension between foam oil and continuous gas are ignored; rock compressibility is ignored, and it is assumed that the fluid obeys constant temperature Darcy flow;

[0050] A second processing unit is used to set the fluid motion equations of the foam oil and the continuous gas;

[0051] The third processing unit is used to set a calculation method for physical property parameters of the foam oil;

[0052] The fourth processing unit is used to set the time-varying dynamic mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas;

[0053] The fifth processing unit is used to establish a two-phase four-component seepage mathematical model of foam oil based on the set fluid flow equation, physical property parameter calculation method, and the mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas;

[0054] The sixth processing unit is used to give the initial conditions and boundary conditions of the heavy oil reservoir and discretize the two-phase four-component seepage mathematical model;

[0055] The sixth processing unit is used to perform a fully implicit solution to the discrete two-phase four-component seepage mathematical model to obtain the distribution of unknown quantities in each grid in the heavy oil reservoir and the well production.

[0056] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the steps of the above-mentioned method for numerical simulation of foamy oil in heavy oil reservoirs are implemented.

[0057] A fourth aspect of 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 implements the steps of the above-mentioned heavy oil reservoir foam oil numerical simulation method when executing the computer program.

[0058] The present invention adopts the above technical solution, which has the following advantages:

[0059] 1. The present invention designs a four-component time-varying numerical simulation method that considers solvent mass transfer and dynamic exchange between solvent and gas. The mathematical model constructed takes into account the dynamic characteristics of gas exchange, including the effect of heavy oil viscosity on dissolved gas release, the effect of heavy oil viscosity and dispersed bubble content on dispersed bubble aggregation, and finally combines the finite difference method and Newton-Raphson iteration for a fully implicit solution.

[0060] 2. The simulation method of the present invention is more consistent with the actual seepage situation of foamy oil in heavy oil reservoirs, and provides a new theoretical basis for the numerical simulation of foamy oil in heavy oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 A schematic diagram of a quasi-single-phase foam oil provided in one embodiment of the present invention;

[0062] Figure 2 A calculation flow chart of a method for numerical simulation of foamy oil in heavy oil reservoirs provided by this embodiment of the present invention;

[0063] Figure 3 is the fitting result of Example 1 of the present invention;

[0064] Figure 4 A schematic diagram of a solvent throughput reservoir model and a concentration-pressure profile provided in this embodiment of the present invention;

[0065] Figure 5 This is a recovery factor variation diagram of Example 2 of the present invention;

[0066] Figure 6 This is a relationship diagram between the oil production rate and the gas production rate in Example 2 of the present invention. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work are within the scope of protection of the present invention.

[0068] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "first", "second", "third", "fourth" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" and the like mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" and the like are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0069] Based on the problems existing in existing theories and methods, the present invention designs a four-component time-varying numerical simulation method that considers solvent mass transfer and dynamic exchange between solvent and gas. The mathematical model constructed takes into account the dynamic characteristics of gas exchange, including the influence of heavy oil viscosity on dissolved gas release, the influence of heavy oil viscosity and dispersed bubble content on dispersed bubble aggregation, and finally combines the finite difference method and Newton-Raphson iteration for a fully implicit solution.

[0070] The technical solution of the present invention is described below in conjunction with specific embodiments.

[0071] The time-varying numerical simulation method and fully implicit solution scheme considering solvent mass transfer and dynamic exchange between solvent and gas involved in the present invention specifically include:

[0072] Step 1: Set the assumptions:

[0073] 1) Foam oil as a pseudo-single phase (such as Figure 1 As shown in the figure, it contains three components: degassed oil, dissolved gas and dispersed bubbles. The mixture of degassed oil and dissolved gas is diluent oil, and the flow rate of dispersed bubbles in foam oil is the same as that of diluent oil; 2) dispersed bubbles gather and form continuous gas, and then the fluid is divided into two phases: foamy oil and continuous gas; 3) the interfacial tension between diluent oil and dispersed bubbles in foamy oil, and the interfacial tension between foamy oil and continuous gas are ignored; 4) rock compressibility is ignored, and the flow is assumed to obey constant temperature Darcy flow.

[0074] Step 2, set the fluid motion equation:

[0075] The motion equations of foamy oil and continuous gas obey Darcy's law:

[0076]

[0077]

[0078] Where p is the pressure variable, Pa; ρ fo , fgis the density of foam oil and continuous gas, kg / m 3 ; H is the depth, m; g is the acceleration due to gravity, N / kg; v fo 、v fg are the seepage velocities of foam oil and continuous gas, m / s; μ fo , μ fg are the viscosities of foam oil and continuous gas, mPa·s; K rfo , K rfg are the relative permeabilities of foam oil and continuous gas, dimensionless; K is the absolute permeability, μm 2 ; is the Hamiltonian operator. The relative permeability K is provided by experimental data. If there is no experimental data, it can be calculated according to the following method:

[0079]

[0080]

[0081] In the formula, K rfoc , K rfgc are the endpoint relative permeabilities of foamy oil and continuous gas, dimensionless; n fo 、n fg are the phase permeability indexes of foam oil and continuous gas, dimensionless; s fo * Effective saturation of foam oil:

[0082]

[0083] In the formula, s gc 、s or 、s wi is the critical gas saturation, residual oil saturation, and irreducible water saturation, dimensionless; s fo is the foam oil saturation, dimensionless.

[0084] Step 3, set the calculation method of the physical property parameters of the foam oil:

[0085] The density of foam oil is determined by the density and mass fraction of degassed oil, dissolved gas, and dispersed bubbles:

[0086]

[0087] In the formula, x do 、x sg 、x dg are the mass fractions of degassed oil, dissolved gas, and dispersed bubbles, respectively, dimensionless; ρ do , sg , dg are the densities of deaerated oil, dissolved gas, and dispersed bubbles, kg / m 3; The dispersed bubble density is calculated according to the gas state equation, and the degassed oil density and dissolved gas density are determined by their isothermal compression coefficients:

[0088]

[0089]

[0090] In the formula, p r is the reference pressure, Pa; and Represents the density of degassed oil and dissolved gas at reference pressure, kg / m 3 ; C do , C sg are the isothermal compressibility coefficients of degassed oil and dissolved gas, 1 / MPa, respectively.

[0091] Step 4, set the mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas:

[0092] R sg→dg =F sg→dg φs fo f o c sup M sg ×10 -3 (9)

[0093] R dg→fg =F dg→fg φs fo f dg ρ dg (10)

[0094] In the formula, R sg→dg and R dg→fg represent the mass transfer rate from dissolved gas to dispersed bubbles and from dispersed bubbles to continuous gas, kg / (s·m 3 );F sg→dg and F dg→fg are the reaction rate constants of the two mass transfer processes, 1 / s; φ is the porosity, dimensionless; f o 、f dg are the volume fractions of diluent oil and dispersed bubbles in foamy oil, dimensionless; M sg is the molar mass of dissolved gas, kg / mol; c sup is the supersaturation concentration, mol / m 3 , the calculation method is as follows:

[0095] c sup =max(0,[sg] t -[sg] equ ) (11)

[0096] In the formula, [sg]t Represents the concentration of dissolved gas in the diluent oil at time t, mol / m 3 ; [sg] equ Represents the concentration of dissolved gas in the diluent oil under equilibrium state at time t, that is, the saturated concentration of dissolved gas corresponding to the pressure at time t, mol / m 3 ;

[0097] The growth rate of bubbles is related to the diffusion coefficient. The smaller the viscosity of the diluent oil, the larger the diffusion coefficient, and the faster the transformation and growth rate of the bubbles. sg→dg is a function of the diluent oil viscosity:

[0098]

[0099] The low viscosity diluent oil has a smaller viscosity on the dispersed bubbles and a poorer binding ability, so the dispersed bubbles are more likely to coalesce. In addition, when the volume fraction of the dispersed bubbles is small, it is not easy to coalesce. Therefore, F dg→fg is a function of the dilution oil viscosity and the dispersed bubble volume fraction:

[0100]

[0101] In the formula, F sg→dg_base and F dg→fg_base is the cardinality term of the reaction rate constant, 1 / s; μ do is the viscosity of the degassed oil, mPa·s; μ o is the viscosity of the dilution oil, mPa·s; f dg is the volume fraction of dispersed bubbles in foamy oil, dimensionless; m and n represent the correlation, which can be obtained through experiments or fitting, dimensionless.

[0102] Step 5: Establish a two-phase four-component seepage mathematical model, where the two phases are foam oil and continuous gas, and the four components are degassed oil, dissolved gas, dispersed bubbles, and continuous gas. Based on the law of mass conservation, the two-phase four-component continuity equation is derived:

[0103] Deaerated oil:

[0104]

[0105] Dissolved gas:

[0106]

[0107] Dispersed bubbles:

[0108]

[0109] Continuous gas:

[0110]

[0111] In the formula, qfo ,q fg are the outlet outputs of foam oil and continuous gas, kg / s; D is the diffusion coefficient of dissolved gas in the diluent oil, m 2 / s; c is the mass concentration of dissolved gas in the diluent oil, kg / m 3 ;s fg is the continuous gas saturation, dimensionless.

[0112] The sum of the foamy oil and continuous gas saturation is 1:

[0113] s fo +s fg =1 (18)

[0114] The sum of the mass fractions of the three components in the foam oil is 1:

[0115] x do +x sg +x dg =1 (19)

[0116] The conversion relationship between dissolved gas mass concentration and mass fraction is:

[0117]

[0118] According to the auxiliary conditions, the independent variables of the equation system are p, x sg 、x dg and fo .

[0119] Step 6: Given the initial conditions and boundary conditions, and discretize the seepage mathematical model:

[0120] The initial pressure and initial saturation of the reservoir are the initial conditions; the outer boundary is a closed boundary, and the inner boundary can be a constant pressure or constant production. The discrete mathematical model is as follows: First, define the phase conductivity and solution gas diffusion rate:

[0121]

[0122]

[0123] In the formula, k represents a phase, fo is foam oil, fg is continuous gas; T x，k , T y，k , T z，k K is the conductivity of phase k in the x, y, and z directions, kg / (Pa·s); rfk is the relative permeability of phase k, dimensionless; ρ k is the k-phase density, kg / m 3 ; k is the k-phase viscosity, mPa·s; G x D. G y D. Gz D are the dissolved gas diffusion rates in the x, y and z directions, m 3 / s; Δx, Δy, Δz are the spatial steps in the x, y, and z directions, respectively, m. The second-order difference quotient operator in the x direction is defined as follows, and the same is true for the y and z directions:

[0124]

[0125] In the formula, com represents a component in the foam oil, do, sg, and dg represent degassed oil, dissolved gas, and dispersed bubbles, respectively; the subscripts (i, j, k), (i-1, j, k), and (i+1, j, k) represent grid numbers, respectively; (i+1 / 2, j, k), and (i-1 / 2, j, k) represent auxiliary points, respectively; x com is the mass fraction of component com, dimensionless; γ fo and γ fg are the weights of foam oil and continuous gas, N / m 3 For closed boundaries, each second-order difference quotient operator in the above formula contains only one term, which is related to the boundary position. Fluid potential φ k =p-γ k H, the auxiliary point value is selected according to the windward format:

[0126]

[0127]

[0128] With the above description, the continuity equation of the grid (i, j, k) is discretized as follows:

[0129] Deaerated oil:

[0130]

[0131] Dissolved gas:

[0132]

[0133] Dispersed bubbles:

[0134]

[0135] Continuous gas:

[0136]

[0137] Where n and n+1 are time steps; the subscript well indicates whether there is a well in the grid. If there is a well, the term exists; Δt is the time step, s; V is the volume of the grid block, m 3 .

[0138] Step 7, fully implicit solution:

[0139] When solving the nth to n+1th time step, several iterations are required. First, the residual equation of the lth step is given, that is, the superscript n+1 in the formula is changed to l, and then the right side of the equation is moved to the left side, so that the right side of the equation is 0, indicating the state of the lth step. When producing at a constant pressure or a constant pressure exhaustion rate, if the number of grids is N, the grid fast unknown quantity and the residual equation vector are recorded as:

[0140]

[0141]

[0142] In the formula, X is the unknown vector; F is the residual equation vector; p, x sg 、x dg 、s fo is the vector of unknown quantities; F do 、F sg 、F dg 、F fg is the vector of each residual equation. Iterate and solve according to the following formula:

[0143]

[0144] Among them, δ represents the increment, and the unknown quantity increment vector is:

[0145]

[0146] The Jacobian matrix can be divided into sixteen blocks, which are the first-order partial derivative matrices of the residual equations corresponding to the four components with respect to the four unknown quantities. The formula can be expanded to:

[0147]

[0148] In the formula, J F,x It means that the residual equation F is partial derivative of the unknown quantity x, such as:

[0149]

[0150] When the production is constant, the bottom hole pressure is an unknown quantity. We only need to increase the number of unknown quantities and residual equations by n (n wells are produced at constant production). Similarly, the dimension of the Jacobian matrix is ​​increased by n to ensure that the additional production residual equations can be used to obtain partial derivatives of each unknown quantity and each residual equation can be used to obtain partial derivatives of the bottom hole pressure.

[0151] When solving the nth to n+1th step, take the initial value of the iteration as the value of the nth step, p, x sg 、x dg and fo The accuracy is [5Pa,1×10 -6 ,1×10 -6 ,1×10 -6]. When the accuracy is reached, the calculation of this time step ends.

[0152] Figure 2 This is a simulation calculation flow chart. First, the inner and outer boundaries are given, and the initial values ​​are assigned to the unknown quantities. Then the unknown quantities of the next time step are calculated: the initial value of the iteration (Formula (30)) is taken as the value of the previous time step, the fluid physical parameters and the residual equation (31) are calculated, the Jacobian matrix is ​​obtained according to Formula (35), and the unknown quantity increment of this iteration step is calculated according to Formula (34). Determine whether the unknown quantity increment reaches the convergence accuracy. If not, update the unknown quantity according to Formula (32) and perform the next iteration step calculation within this time step; if the accuracy has been reached, jump out of this time step. Finally, determine whether the end of the simulation period has been reached, that is, whether the simulation time t is less than t max If it has been reached, the simulation ends; if it has not been reached, the next time step calculation is performed.

[0153] The technical solution of the present invention is further explained below in conjunction with specific application examples.

[0154] Example 1: Foamy oil flow in depletion production.

[0155] To simulate the one-dimensional sand-filled pipe experiment, a horizontal sand-filled pipe is first set up, and several pressure measuring points are placed along the way; a small opening is opened on the left side of the sand-filled pipe, and a high-precision pump is used to control the outlet pressure exhaustion rate to be constant for production.

[0156] The experimental parameters are as follows.

[0157] Table 1 Experimental parameters

[0158]

[0159] The fluid fitting parameters are as follows:

[0160] Table 2 Fluid parameter fitting

[0161]

[0162] The two-phase production can be calculated by the phase flow coefficient and the pressure difference between the first grid adjacent to the pressure relief port and the pressure relief port:

[0163]

[0164]

[0165] Where p1 is the pressure of the first grid, Pa; p left is the pressure at the pressure relief port, Pa;

[0166] Adjusting the two reaction rate constant base terms (Table 3), the fitting results obtained are as follows Figure 3 . R of experimental and simulated data of oil and gas2 The values ​​are 0.97 and 0.89 respectively, indicating that the model can simulate the foam oil phenomenon well. The oil recovery rate can be divided into three stages: ① Stage A: above the bubble point pressure, the pressure in this stage is higher than the bubble point pressure, and it is completely driven by the elastic properties of heavy oil. Due to the high viscosity, the seepage resistance is high, and the production is at an extremely low value; ② Stage B: when the pressure is lower than the bubble point pressure, the dissolved gas is released to form dispersed bubbles, and foam oil is formed with the heavy oil. The pressure gradient and seepage velocity in the sand filling pipe gradually increase, and the production gradually increases; ③ Stage C: the continuous gas saturation formed in stage B gradually increases, and the continuous gas seepage velocity is higher than the foam oil seepage velocity, causing gas channeling, so the oil production increase rate gradually slows down.

[0167] Table 3 Simulation parameters

[0168]

[0169] Example 2: Foamy oil flow in solvent huff and puff.

[0170] Figure 4 The figure is a one-dimensional reservoir model for solvent production, and a schematic diagram of the distribution of pressure and concentration at the end of the soaking. The entire model is divided into three parts: the solvent cavity; the transition zone of solvent dilution; and the uncontacted crude oil zone. During the production phase, due to the drop in bottom hole pressure, the pressure on the entire model will be redistributed, which will lead to the release of dissolved gas in the transition zone and the occurrence of non-equilibrium phenomena, that is, the generation of foamy oil behavior. The gas zone is ignored in this example, aiming to simulate the foamy oil flow in the solvent huff-and-puff production stage. The example parameters are shown in Table 4.

[0171] Table 4 Operating parameters of solvent huff and puff production stage

[0172]

[0173] Figure 5 , Figure 6 The changes in oil and gas recovery rate and oil and gas production rate during the simulation are shown. It can be seen that the change in production is step-like and the production rate shows multiple peaks. Since the existence of gas cavity is not considered in this physical model, the increase in production can be regarded as the forward advancement of the fluid front in the transition zone. Therefore, Figure 4 It reflects the multi-wave flow at the fluid front in the sand-filled pipe.

[0174] The reason why the flow is induced is due to the appearance of bubbles at the front edge. The presence of bubbles helps to increase the pressure gradient, thereby inducing rapid flow of the fluid at the front edge of the transition zone, thereby increasing production. As the pressure decreases further, on the one hand, the viscosity of the oil phase gradually increases due to the release of gas, and on the other hand, the bubbles gradually gather and gas channeling occurs, and the production decreases. When the pressure drops further, bubbles are generated in a deeper position in the dilution zone, inducing foam oil flow again, which is similar to the above process.

[0175] A second aspect of the present invention provides a heavy oil reservoir foam oil numerical simulation device, comprising:

[0176] The first processing unit is used to set assumptions based on foam oil. The assumptions are as follows: foam oil is a pseudo-single phase and contains three components: degassed oil, dissolved gas and dispersed bubbles, wherein the mixture of degassed oil and dissolved gas is diluent oil, and the flow rate of dispersed bubbles in foam oil is the same as that of diluent oil; dispersed bubbles gather and form continuous gas, at which time the fluid is divided into two phases: foam oil and continuous gas, and the interfacial tension between diluent oil and dispersed bubbles in foam oil and the interfacial tension between foam oil and continuous gas are ignored; rock compressibility is ignored, and it is assumed that the fluid obeys constant temperature Darcy flow;

[0177] A second processing unit is used to set the fluid motion equations of the foam oil and the continuous gas;

[0178] The third processing unit is used to set a calculation method for physical property parameters of the foam oil;

[0179] The fourth processing unit is used to set the time-varying dynamic mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas;

[0180] The fifth processing unit is used to establish a two-phase four-component seepage mathematical model of foam oil based on the set fluid motion equation, physical property parameter calculation method, and the mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas;

[0181] The sixth processing unit is used to give the initial conditions and boundary conditions of the heavy oil reservoir and discretize the two-phase four-component seepage mathematical model;

[0182] The sixth processing unit is used to perform a fully implicit solution to the discrete two-phase four-component seepage mathematical model to obtain the distribution of unknown quantities in each grid in the heavy oil reservoir and the well production.

[0183] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the steps of the above-mentioned method for numerical simulation of foamy oil in heavy oil reservoirs are implemented.

[0184] A fourth aspect of 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 implements the steps of the above-mentioned heavy oil reservoir foam oil numerical simulation method when executing the computer program.

[0185] The present invention is described in terms of flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to specific embodiments. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes 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 a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0186] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0187] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0188] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for numerical simulation of foam oil in heavy oil reservoirs, characterized in that: include: Based on foamy oil, the assumptions are as follows: foamy oil is a pseudo-single phase, containing three components: degassed oil, dissolved gas and dispersed bubbles, where the mixture of degassed oil and dissolved gas is diluent oil, and the flow rate of dispersed bubbles in foamy oil is the same as that of diluent oil; dispersed bubbles gather to form continuous gas, at which time the fluid is divided into two phases: foamy oil and continuous gas, ignoring the interfacial tension between diluent oil and dispersed bubbles in foamy oil, and ignoring the interfacial tension between foamy oil and continuous gas; ignoring rock compressibility, and assuming that the fluid obeys constant temperature Darcy flow; Set the fluid motion equations for foamy oil and continuous gas; Set the calculation method of the physical property parameters of foam oil; Set the time-varying dynamic mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas; Based on the set fluid motion equation, physical property parameter calculation method, and the mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas, a two-phase four-component seepage mathematical model of foamy oil is established. Given the initial and boundary conditions of heavy oil reservoir, a two-phase four-component flow mathematical model is discretized; The discrete two-phase four-component seepage mathematical model is solved implicitly to obtain the unknown quantity distribution of each grid in the heavy oil reservoir and the well production.

2. The method for numerical simulation of foamy oil in heavy oil reservoirs according to claim 1, characterized in that: Set the fluid motion equation as follows: The motion equations of foamy oil and continuous gas obey Darcy's law: Where p is the pressure variable; ρ fo , fg are the density of foam oil and continuous gas respectively; H is the depth; g is the acceleration of gravity; v fo 、v fg are the seepage velocities of foam oil and continuous gas respectively; μ fo , μ fg are the viscosities of foam oil and continuous gas respectively; K rfo , K rfg are the relative permeabilities of foam oil and continuous gas, respectively; K is the absolute permeability; is the Hamiltonian operator.

3. The method for numerical simulation of foamy oil in heavy oil reservoir according to claim 2, characterized in that: The calculation method of the physical property parameters of foam oil is set as follows: The density of foamy oil is determined by the density and mass fraction of degassed oil, dissolved gas, and dispersed bubbles: In the formula, x do 、x sg 、x dg are the mass fractions of degassed oil, dissolved gas, and dispersed bubbles, respectively; ρ do , sg , dg are the densities of degassed oil, dissolved gas, and dispersed bubbles, respectively; The dispersed bubble density is calculated according to the gas state equation, and the degassed oil density and dissolved gas density are determined by their isothermal compression coefficients: In the formula, p r is the reference pressure; and Represents the density of degassed oil and dissolved gas at reference pressure; C do , C sg are the isothermal compressibility coefficients of degassed oil and dissolved gas, respectively.

4. The method for numerical simulation of foamy oil in heavy oil reservoirs according to claim 3, characterized in that: The time-varying dynamic mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas is set as follows: R sg→dg =F sg→dg φs fo f o c sup M sg ×10 -3 R dg→fg =F dg→fg φs fo f dg ρ dg In the formula, R sg→dg and R dg→fg represent the mass transfer rate from dissolved gas to dispersed bubbles and from dispersed bubbles to continuous gas respectively; F sg→dg and F dg→fg is the reaction rate constant; c sup is the supersaturation concentration; f o and f dg are the volume fractions of diluent oil and dispersed bubbles in foam oil, respectively; φ is the porosity; M sg is the molar mass of dissolved gas; s fo is the foam oil saturation; The smaller the viscosity of the diluent oil, the larger the diffusion coefficient, and the faster the transformation and growth of the bubbles. sg→dg is a function of the diluent oil viscosity: The low viscosity diluent oil has a smaller viscosity force on the dispersed bubbles and a poorer binding ability, so the dispersed bubbles are more likely to coalesce. In addition, when the volume fraction of the dispersed bubbles is small, it is not easy to coalesce. Therefore, F dg→fg is a function of the dilution oil viscosity and the dispersed bubble volume fraction: In the formula, F sg→dg_base and F dg→fg_base is the cardinality term of the reaction rate constant; μ do is the viscosity of degassed oil; μ o is the viscosity of the diluent oil; f dg is the volume fraction of dispersed bubbles in foamy oil; m and n represent the correlation degree.

5. The method for numerical simulation of foamy oil in heavy oil reservoirs according to claim 4, characterized in that: A two-phase four-component seepage mathematical model of foam oil is established, as follows: According to the law of mass conservation, the two-phase four-component continuity equation is derived: Deaerated oil: Dissolved gas: Dispersed bubbles: Continuous gas: In the formula, q fo ,q fg are the outlet outputs of foam oil phase and continuous gas, respectively; D is the diffusion coefficient of dissolved gas in diluent oil; c is the mass concentration of dissolved gas in diluent oil; s fg is the continuous gas saturation.

6. A device for numerical simulation of foam oil in heavy oil reservoirs, characterized in that: include: The first processing unit is used to set assumptions based on foam oil. The assumptions are as follows: foam oil is a pseudo-single phase and contains three components: degassed oil, dissolved gas and dispersed bubbles, wherein the mixture of degassed oil and dissolved gas is diluent oil, and the flow rate of dispersed bubbles in foam oil is the same as that of diluent oil; dispersed bubbles gather and form continuous gas, at which time the fluid is divided into two phases: foam oil and continuous gas, and the interfacial tension between diluent oil and dispersed bubbles in foam oil and the interfacial tension between foam oil and continuous gas are ignored; rock compressibility is ignored, and it is assumed that the fluid obeys constant temperature Darcy flow; A second processing unit is used to set the fluid motion equations of the foam oil and the continuous gas; The third processing unit is used to set a calculation method for physical property parameters of the foam oil; The fourth processing unit is used to set the time-varying dynamic mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas; The fifth processing unit is used to establish a two-phase four-component seepage mathematical model of foam oil based on the set fluid motion equation, physical property parameter calculation method, and the mass transfer rate of dissolved gas escaping to form dispersed bubbles and dispersed bubbles merging to form continuous gas; The sixth processing unit is used to give the initial conditions and boundary conditions of the heavy oil reservoir and discretize the two-phase four-component seepage mathematical model; The sixth processing unit is used to perform a fully implicit solution to the discrete two-phase four-component seepage mathematical model to obtain the distribution of unknown quantities in each grid in the heavy oil reservoir and the well production.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for numerical simulation of foamy oil in heavy oil reservoirs according to any one of claims 1 to 5 are implemented.

8. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for numerical simulation of foamy oil in heavy oil reservoirs according to any one of claims 1 to 5 are implemented.

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