CN116468188A - Dynamic prediction method for paraffin precipitation phase state of condensate gas reservoir in constant volume failure - Google Patents
Dynamic prediction method for paraffin precipitation phase state of condensate gas reservoir in constant volume failure Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 86
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- 239000012188 paraffin wax Substances 0.000 title claims description 7
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Abstract
The invention aims to provide a dynamic prediction method of a condensate gas reservoir wax phase state in constant volume failure, and aims at the condensate gas reservoir failure exploitation process, a solid phase state calculation method for summarizing the condensate gas reservoir dynamic phase state change is established by considering the stratum fluid component change, utilizing a phase balance theory and combining a PR state equation according to the substance balance theory, so that the vacancy research of the condensate gas reservoir failure process at home and abroad is made up.
Description
Technical Field
The invention relates to the field of fluid phase analysis, in particular to a dynamic prediction method for a phase state of a condensate gas reservoir wax in constant volume failure.
Background
The land shale condensate gas reservoirs of the Sichuan basin are rich in reserves, and the gas fields such as pelage dams, fuling and the like have the characteristics of large shale burial depth and higher wax content. The higher wax content easily causes wax deposition phenomenon in stratum and shaft, and causes serious production reduction of gas well and even well shutdown and safety accident.
With the production and exploitation, the formation pressure is continuously reduced, the formation fluid components and the corresponding phase state changes, and the phase state changes of the condensate gas reservoir wax precipitation in the failure exploitation process need to be accurately predicted, so as to guide the design of a wellhead and a ground matching device. At present, the research on the dynamic phase change of the failure process of the condensate gas reservoir at home and abroad is perfect, but the research on the phase change of the condensate wax in the failure process is less, and the following problems exist:
(1) Aiming at the dynamic phase state change of the condensate gas reservoir, the prior method mainly calculates the gas-liquid two-phase state change without considering the solid phase state;
(2) Aiming at the problem of wax precipitation phase, the existing method is basically based on the prediction calculation of the original formation fluid in the early period of gas reservoir exploitation, and the change of the formation fluid composition in the failure process is not considered.
Disclosure of Invention
The invention aims to provide a method for dynamically predicting the wax phase state of a condensate gas reservoir in constant volume failure, and aims to establish a dynamic prediction model of the wax phase state of the condensate gas reservoir according to a material balance theory by taking the component change of stratum fluid into consideration, utilizing a phase balance theory and combining a PR state equation and the material balance theory in the recovery process of the condensate gas reservoir.
A dynamic prediction method for the paraffin precipitation phase state of a condensate gas reservoir in constant volume failure comprises the following steps:
s1: inputting original data according to initial conditions, wherein the original data comprises system composition, thermodynamic parameters and calculated temperature and pressure;
s2: splitting and recombining components of the added fraction by a heavy fraction characterization method to obtain various compositions and thermodynamic parameters of the quasi-components;
s3: flash evaporation calculation under saturation pressure is carried out, and a constant volume V is determined;
s4: performing constant volume failure calculation under the current failure pressure, calculating the mole fraction and the composition of each phase, determining the volume V' under the failure pressure, discharging gas to enable the total volume to return to the constant volume V, and updating the fluid composition;
s5: calculating a wax analysis phase state of the new fluid component under the failure pressure, and calculating a phase envelope curve and a wax analysis curve;
s6: and (3) carrying out single degassing flash evaporation calculation on the liquid phase part of the new fluid component under the failure pressure to obtain a degassing oil component composition, and carrying out wax precipitation phase state calculation on the degassing oil component.
S7: the updated component is a new fluid component under the failure pressure, the updated pressure is the next stage failure pressure, and the S4 is returned;
s8: and (5) meeting the temperature and pressure convergence condition, and completing calculation.
Further, the step S1 comprises substituting various parameters of the condensate gas reservoir into a condensate gas reservoir wax phase prediction model, wherein initial values are components, physical parameters and original formation temperature and pressure of original formation fluid.
Further, a dynamic prediction method of a condensate gas reservoir wax phase state in constant volume failure is provided, wherein the heavy fraction characterization method is based on a mathematical statistics theory, and a mole fraction distribution rule of an oil sample is counted by using mole fractions of the first n-1 components in a liquid phase component to obtain a mathematical model; the extended fraction of the heavy fraction was calculated using the mathematical model and the SCN fraction content was determined.
Further, a dynamic prediction method for a paraffin precipitation phase state of a condensate gas reservoir in constant volume failure, S2 comprises the following substeps:
s21: number of carbon number exceedsWhen the carbon number of the reservoir fluid is +/corresponding mole fraction>In an approximately linear relationship:
；
wherein A, B represents a constant, and A, B can be obtained by adopting a least square method when the component normal boiling point temperature or the molar mass data exist;
wherein the method comprises the steps ofRepresents a mole fraction;
s22: the distribution function divides the positive score, and the calculation formula is:
；
wherein the method comprises the steps ofRepresents carbon number, & lt + & gt>Representing density, & lt + & gt>Represents->Molecular weight of carbon number, C, D, represents fitting parameters;
s23: after the composition of each extension component is obtained, thermodynamic physical parameters of each component are calculated by selecting corresponding relations, wherein the thermodynamic physical parameters comprise molar mass, normal boiling point temperature, critical pressure, eccentric factor, critical temperature and specific gravity, single carbon array components are combined into a quasi-component, and the calculation formula is as follows:
；
wherein the method comprises the steps ofRepresents an eccentricity factor;
wherein the method comprises the steps of，/>Represents the local atmospheric pressure and critical pressure in MPa;
wherein the method comprises the steps of，/>Represents critical temperature and normal boiling point, unit K;
wherein the method comprises the steps ofRepresents->Fraction relative molecular mass, < >>Represents->Fraction relative density;
the calculated independent variables are critical temperature, critical pressure and normal boiling point temperature.
Further, a dynamic prediction method for the wax phase state of the condensate gas reservoir in constant volume failure is provided, and the flash evaporation of the phase state of the condensate gas reservoir is calculated through a gas-liquid-solid three-phase equilibrium thermodynamic model, and comprises the following substeps of:
s31, setting up an oil-gas system consisting of n components, taking 1mol of mass number as an analysis unit, and when the system is in gas-liquid-solid three-phase balance, the following material balance conditions are satisfied:
；
wherein V represents the gas phase at equilibrium, L represents the liquid phase, S represents the mass fraction of the solid phase;
wherein the method comprises the steps ofRepresents the molar composition of the ith component in the gas phase at equilibrium, (-) in each case>Represents the molar composition of the i-th component of the liquid phase, in terms of->Represents the molar composition of the i-th component in each of the solid phases;
wherein the method comprises the steps ofRepresents the total molar composition of the ith component in the oil and gas system;
s32: when the system reaches phase equilibrium, the temperature of each phase in the systemTPressure and forcePAnd the fugacity degreefThe gas-liquid-solid phases are equal, and when the gas-liquid-solid phases are in phase equilibrium, the following formula is satisfied:
；
wherein V, L, S superscript represents the parameters of component i in the gas phase, liquid phase and solid phase, respectively;
the state equation is used for describing the fugacity of the gas phase and the liquid phase, and the solution theory describes the fugacity in the solid phase as follows:
；
wherein the method comprises the steps ofRepresents the molar content of component i in the gas phase,/->Represents the molar content of component i in the liquid phase, (-)>Represents the molar content of component i in the solid phase in mol%;
wherein the method comprises the steps ofRepresenting the fugacity coefficient of component i in the gas phase, ">Representing the fugacity coefficient of component i in the liquid phase,/->Representing the activity coefficient of component i in the solid phase;
wherein the method comprises the steps ofRepresenting the standard fugacity of the solid phase of the component i under certain temperature and pressure conditions, wherein the unit is MPa;
the definition of the equilibrium constant is as follows:
；
wherein the method comprises the steps ofRepresents the equilibrium constant of gas and liquid->Is a solid-liquid equilibrium constant;
the formula can be used for deducing a gas-liquid-solid three-phase balance numerical model equation set as follows:
；
the gas-liquid-solid three-phase balance numerical model equation set is highly nonlinear, and according to balance constants of components in each phase during balance, the equation set can be solved in a combined mode, and the balance mole components of each gas-liquid-solid phase can be calculated to form each phase mole;
flash evaporation calculation is carried out to determine the volume of a condensate gas sample under the saturation pressure, and the volume at the moment is the volume of a constant volume。
Further, a dynamic prediction method for wax phase state of condensate gas reservoir in constant volume failure, wherein the constant volume failure calculates to obtain mole fraction and composition of each phase, and calculates the volume of each phase under the current failure pressure, and the gas phase volume is reduced S31, wherein an oil gas system composed of n components is established, 1 mole mass number is taken as an analysis unit, and when the system is in gas-liquid-solid three-phase balance, the following material balance conditions should be satisfied:
；
wherein V represents the gas phase at equilibrium, L represents the liquid phase, S represents the mass fraction of the solid phase;
wherein the method comprises the steps ofRepresents the molar composition of the ith component in the gas phase at equilibrium, (-) in each case>Represents the molar composition of the i-th component of the liquid phase, in terms of->Represents the molar composition of the i-th component in each of the solid phases;
wherein the method comprises the steps ofRepresents the total molar composition of the ith component in the oil and gas system;
s32: when the system reaches phase equilibrium, the temperature of each phase in the systemTPressure and forcePAnd the fugacity degreefThe gas-liquid-solid phases are equal, and when the gas-liquid-solid phases are in phase equilibrium, the following formula is satisfied:
；
wherein V, L, S superscript represents the parameters of component i in the gas phase, liquid phase and solid phase, respectively;
the state equation is used for describing the fugacity of the gas phase and the liquid phase, and the solution theory describes the fugacity in the solid phase as follows:
；
wherein the method comprises the steps ofRepresents the molar content of component i in the gas phase,/->Represents the molar content of component i in the liquid phase, (-)>Represents the molar content of component i in the solid phase in mol%;
wherein the method comprises the steps ofRepresenting the fugacity coefficient of component i in the gas phase, ">Representing the fugacity coefficient of component i in the liquid phase,/->Representing the activity coefficient of component i in the solid phase;
wherein the method comprises the steps ofRepresenting the standard fugacity of the solid phase of the component i under certain temperature and pressure conditions, wherein the unit is MPa;
the definition of the equilibrium constant is as follows:
；
wherein the method comprises the steps ofRepresents the equilibrium constant of gas and liquid->Is a solid-liquid equilibrium constant;
the formula can be used for deducing a gas-liquid-solid three-phase balance numerical model equation set as follows:
；
the gas-liquid-solid three-phase balance numerical model equation set is highly nonlinear, and according to balance constants of components in each phase during balance, the equation set can be solved in a combined mode, and the balance mole components of each gas-liquid-solid phase can be calculated to form each phase mole;
flash calculation determines the volume of the condensate sample at saturation pressure, at this timeThe volume is a constant volume。
Further, a dynamic prediction method for the wax phase state of a condensate gas reservoir in constant volume failure is provided, wherein the constant volume failure is calculated to obtain the mole fraction and the composition of each phase, the volume of each phase under the current failure pressure is calculated, and the volume of the gas phase is reducedThe remaining phase volumes remain unchanged and the fluid composition after venting is calculated from the new phase fractions.
Further, the step S5 comprises updating the temperature on the basis of a flash evaporation model until the solid phase precipitation temperature is the wax precipitation temperature of the current condition, adjusting the pressure, and repeating the process to calculate a wax precipitation curve of the flash evaporation component.
Further, the step S5 comprises the step of carrying out single degassing flash evaporation calculation on the liquid phase part of the residual fluid component under the failure pressure to obtain a degassing oil component composition, carrying out wax phase state calculation, and simulating the extraction process of the condensate reverse condensate of the condensate gas reservoir.
The invention has the beneficial effects that: according to the method, the composition change of stratum fluid is considered in the recovery process of the condensate gas reservoir failure, the composition change in the failure process is considered, the result is closer to an actual value, the vacancy research of the recovery process of the condensate gas reservoir at home and abroad is made up, and the solid phase state calculation method of the condensate gas reservoir dynamic phase state change is summarized.
Drawings
FIG. 1 is a flow chart of the present invention.
Fig. 2 is a schematic diagram of the constant volume failure process.
Detailed Description
For a clearer understanding of technical features, objects, and effects of the present invention, a specific embodiment of the present invention will be described with reference to the accompanying drawings.
As shown in fig. 1, a dynamic prediction method for the wax phase state of a condensate gas reservoir in constant volume failure comprises the following steps:
s1: raw data, including system composition and thermodynamic parameters, are input according to initial conditions, and calculated temperature and pressure are input.
Substituting each parameter of the condensate gas reservoir into a condensate gas reservoir wax phase prediction model, wherein the initial values are the components, physical parameters and original formation temperature and pressure of the original formation fluid.
S2: splitting and recombining the components of the added fraction by a heavy fraction characterization method to obtain each component of the quasi-component and thermodynamic parameters thereof.
Modern experimental techniques are limited, and it is not possible to accurately measure the composition distribution of each component, for the remaining undefined components (e.g、/>Or->) Many complex hydrocarbons, such as long chain alkanes, cycloalkanes, aromatics and their various isomers, are generally available in amounts which are generally only determinable as to their overall content, relative density and molecular mass, and other thermodynamic parameters are difficult to determine directly.
The heavy fraction characterization calculation is based on a mathematical statistics theory, and a mole fraction distribution rule of the oil sample is calculated by utilizing mole fractions of the first n-1 components in the liquid phase components to obtain a mathematical model; the extended fraction of the heavy fraction was calculated using the mathematical model and the SCN fraction content was determined.
Number of carbon number exceedsWhen the carbon number of the reservoir fluid is +/corresponding mole fraction>In an approximately linear relationship:
；
wherein A, B represents a constant, and A, B can be obtained by adopting a least square method when the component normal boiling point temperature or the molar mass data exist;
wherein the method comprises the steps ofRepresents a mole fraction;
the distribution function divides the positive score, and the calculation formula is:
；
wherein the method comprises the steps ofRepresents carbon number, & lt + & gt>Representing density, & lt + & gt>Represents->Molecular weight of carbon number, C, D, represents fitting parameters;
after the composition of each extension component is obtained, the thermodynamic physical parameters of each component are calculated by selecting proper association, wherein the thermodynamic physical parameters comprise molar mass, normal boiling point temperature, critical pressure, eccentric factor, critical temperature and specific gravity.
In order to reduce the component number and simplify the calculation, the single carbon array components are combined into the pseudo component on the premise of ensuring the calculation accuracy so as to reduce the calculation amount:
；
wherein the method comprises the steps ofRepresents an eccentricity factor;
wherein the method comprises the steps of，/>Represents the local atmospheric pressure and critical pressure in MPa;
wherein the method comprises the steps of，/>Represents critical temperature and normal boiling point, unit K;
wherein the method comprises the steps ofRepresents->Fraction relative molecular mass, < >>Represents->Fraction relative density;
the calculated independent variables are critical temperature, critical pressure and normal boiling point temperature, and can be used in combination with other physical parameters.
S3: flash evaporation calculation under saturation pressure is carried out, and a constant volume V is determined;
the condensate gas reservoir phase flash evaporation can be calculated through a gas-liquid-solid three-phase balance thermodynamic model, and the three-phase balance model is as follows:
1) Material balance
An oil-gas system consisting of n components is provided, 1mol of mass number is taken as an analysis unit, and when the system is in gas-liquid-solid three-phase balance, the following material balance conditions are satisfied:
；
wherein V represents the gas phase at equilibrium, L represents the liquid phase, S represents the mass fraction of the solid phase;
wherein the method comprises the steps ofRepresents the molar composition of the ith component in the gas phase at equilibrium, (-) in each case>Represents the molar composition of the i-th component of the liquid phase, in terms of->Represents the molar composition of the i-th component in each of the solid phases;
wherein the method comprises the steps ofRepresents the total molar composition of the ith component in the oil and gas system;
2) Thermodynamic equilibrium
When the system reaches phase equilibrium, the temperature of each phase in the systemTPressure and forcePAnd the fugacity degreefThe gas-liquid-solid phases are equal, and when the gas-liquid-solid phases are in phase equilibrium, the following formula is satisfied:
；
wherein V, L, S superscript represents the parameters of component i in the gas phase, liquid phase and solid phase, respectively;
using the equation of state to describe the fugacity of the gas phase and the liquid phase, the solution theory describes the fugacity in the solid phase as:
；
wherein the method comprises the steps ofRepresents the molar content of component i in the gas phase,/->Represents the molar content of component i in the liquid phase, (-)>Represents the molar content of component i in the solid phase in mol%;
wherein the method comprises the steps ofRepresenting the fugacity coefficient of component i in the gas phase, ">Representing the fugacity coefficient of component i in the liquid phase,/->Representing the activity coefficient of component i in the solid phase;
wherein the method comprises the steps ofRepresenting the standard fugacity of the solid phase of the component i under certain temperature and pressure conditions, wherein the unit is MPa;
from the definition of the equilibrium constant (the liquid phase is chosen as the reference phase):
；
wherein the method comprises the steps ofRepresents the equilibrium constant of gas and liquid->Is a solid-liquid equilibrium constant;
the gas-liquid-solid three-phase balance numerical model equation set can be deduced from the method as follows:
；
the above equation is a highly nonlinear system of equations. According to the equilibrium constants of the components in each phase during equilibrium, the equation set can be solved in a combined way, and the equilibrium molar components of each gas-liquid-solid phase and the molar composition of each phase can be calculated.
Determination of condensate gas at saturation pressure by flash calculationThe volume of the sample, in this case the volume is the constant volume。
As shown in fig. 2, the condensate gas reservoir at the initial temperature and pressure conditions, as the pressure decreases, is reverse condensed out of the liquid phase, and the fluid composition changes as the gas is vented.
S4: constant volume failure calculation under certain failure pressure is carried out, the mole fraction and the composition of each phase are calculated, and the total volume under the failure pressure is determinedThe exhaust gas brings the total volume back to the constant volume +.>Updating the fluid composition;
the mole fraction and composition of each phase can be obtained through constant volume failure calculation, the volume of each phase under the current failure pressure can be calculated, and the volume of the gas phase is reducedThe remaining phase volumes remain unchanged and the fluid composition after venting is calculated from the new phase fractions.
S5: the wax analysis phase state calculation is carried out on the residual fluid components under the failure pressure, and phase envelope curves, wax analysis curves and the like are calculated;
updating the temperature on the basis of the flash model until the solid phase precipitation temperature is the wax precipitation temperature of the current condition, then adjusting the pressure, and repeating the process to calculate a wax precipitation curve of the flash component. In the past wax phase analysis calculation, the original formation fluid is mostly based, the formation pressure is reduced along with the production, and the wax phase calculation of the residual fluid component under the failure pressure is close to the actual situation.
S6: and (3) carrying out single degassing flash evaporation calculation on the liquid phase part of the residual fluid component under the failure pressure to obtain a degassing oil component composition, and carrying out wax precipitation phase state calculation on the degassing oil component.
S7: the updated component is the residual fluid component under the failure pressure, the updated pressure is the next stage failure pressure, and the S4 is returned;
the depletion process is repeated by updating the original formation fluid to the calculated remaining fluid composition.
S8: and (5) meeting the temperature and pressure convergence condition, and completing calculation.
According to the method, the composition change of stratum fluid is considered in the failure exploitation process of the condensate gas reservoir, the composition change in the failure process is considered, the method is closer to an actual value, the vacancy research of the failure process of the condensate gas reservoir at home and abroad is made up, and the solid phase state calculation method of the condensate gas reservoir dynamic phase state change is summarized.
The foregoing has shown and described the basic principles and main features of the present invention and the advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (8)
1. A dynamic prediction method for the paraffin precipitation phase state of a condensate gas reservoir in constant volume failure is characterized by comprising the following steps:
s1: inputting original data according to initial conditions, wherein the original data comprises system composition, thermodynamic parameters and calculated temperature and pressure;
s2: splitting and recombining components of the added fraction by a heavy fraction characterization method to obtain various compositions and thermodynamic parameters of the quasi-components;
s3: flash evaporation calculation under saturation pressure is carried out, and a constant volume V is determined;
s4: performing constant volume failure calculation under the current failure pressure, calculating the mole fraction and the composition of each phase, determining the volume V' under the failure pressure, discharging gas to enable the total volume to return to the constant volume V, and updating the fluid composition;
s5: calculating a wax analysis phase state of the new fluid component under the failure pressure, and calculating a phase envelope curve and a wax analysis curve;
s6: carrying out single degassing flash evaporation calculation on the liquid phase part of the new fluid component under the failure pressure to obtain a degassing oil component composition, and carrying out wax precipitation phase state calculation on the degassing oil component;
s7: the updated component is a new fluid component under the failure pressure, the updated pressure is the next stage failure pressure, and the S4 is returned;
s8: and (5) meeting the temperature and pressure convergence condition, and completing calculation.
2. The method for dynamically predicting the wax phase state of a condensate gas reservoir in constant volume failure according to claim 1, wherein the step S1 comprises substituting various parameters of the shale condensate gas reservoir into a shale condensate gas reservoir wax phase state prediction model, and initial values are components, physical parameters and original formation temperature and pressure of original formation fluid.
3. The dynamic prediction method of the paraffin precipitation phase of the condensate gas reservoir in constant volume failure according to claim 1, wherein the heavy fraction characterization method is based on a mathematical statistics theory, and a mathematical model is obtained by using the mole fraction distribution rule of the oil sample calculated by the mole fractions of the first n-1 components in the liquid phase component; the extended fraction of the heavy fraction was calculated using the mathematical model and the SCN fraction content was determined.
4. A method for dynamic prediction of the paraffin phase of a condensate reservoir in constant volume depletion according to claim 1, wherein S2 comprises the sub-steps of:
s21: number of carbon number exceedsWhen the carbon number of the reservoir fluid is +/corresponding mole fraction>In an approximately linear relationship:
；
wherein A, B represents a constant, and A, B can be obtained by adopting a least square method when the component normal boiling point temperature or the molar mass data exist;
wherein the method comprises the steps ofRepresents a mole fraction;
s22: the distribution function divides the positive score, and the calculation formula is:
；
wherein the method comprises the steps ofRepresents carbon number, & lt + & gt>Representing density, & lt + & gt>Represents->Molecular weight of carbon number, C, D, represents fitting parameters;
s23: after the composition of each extension component is obtained, thermodynamic physical parameters of each component are calculated by selecting corresponding relations, wherein the thermodynamic physical parameters comprise molar mass, normal boiling point temperature, critical pressure, eccentric factor, critical temperature and specific gravity, single carbon array components are combined into a quasi-component, and the calculation formula is as follows:
；
wherein the method comprises the steps ofRepresents an eccentricity factor;
wherein the method comprises the steps of，/>Represents the local atmospheric pressure and critical pressure in MPa;
wherein the method comprises the steps of，/>Represents critical temperature and normal boiling point, unit K;
wherein the method comprises the steps ofRepresents->Fraction relative molecular mass, < >>Represents->Fraction relative density;
the calculated independent variables are critical temperature, critical pressure and normal boiling point temperature.
5. The method for dynamically predicting the wax phase state of a condensate gas reservoir in constant volume failure according to claim 1, wherein the flash evaporation of the wax phase state of the condensate gas reservoir is calculated by a gas-liquid-solid three-phase equilibrium thermodynamic model, and comprises the following substeps of:
s31, setting up an oil-gas system consisting of n components, taking 1mol of mass number as an analysis unit, and when the system is in gas-liquid-solid three-phase balance, the following material balance conditions are satisfied:
；
wherein V represents the gas phase at equilibrium, L represents the liquid phase, S represents the mass fraction of the solid phase;
wherein the method comprises the steps ofRepresents the molar composition of the ith component in the gas phase at equilibrium, (-) in each case>Represents the molar composition of the i-th component of the liquid phase, in terms of->Represents the molar composition of the i-th component in each of the solid phases;
wherein the method comprises the steps ofRepresents the total molar composition of the ith component in the oil and gas system;
s32: when the system reaches phase equilibrium, the temperature of each phase in the systemTPressure and forcePAnd the fugacity degreefThe gas-liquid-solid phases are equal, and when the gas-liquid-solid phases are in phase equilibrium, the following formula is satisfied:
；
wherein V, L, S superscript represents the parameters of component i in the gas phase, liquid phase and solid phase, respectively;
the state equation is used for describing the fugacity of the gas phase and the liquid phase, and the solution theory describes the fugacity in the solid phase as follows:
；
wherein the method comprises the steps ofRepresenting component i in the gas phaseMolar content,/>Represents the molar content of component i in the liquid phase, (-)>Represents the molar content of component i in the solid phase in mol%;
wherein the method comprises the steps ofRepresenting the fugacity coefficient of component i in the gas phase, ">Representing the fugacity coefficient of component i in the liquid phase,/->Representing the activity coefficient of component i in the solid phase;
wherein the method comprises the steps ofRepresenting the standard fugacity of the solid phase of the component i under certain temperature and pressure conditions, wherein the unit is MPa;
the definition of the equilibrium constant is as follows:
；
wherein the method comprises the steps ofRepresents the equilibrium constant of gas and liquid->Is a solid-liquid equilibrium constant;
the formula can be used for deducing a gas-liquid-solid three-phase balance numerical model equation set as follows:
；
the gas-liquid-solid three-phase balance numerical model equation set is highly nonlinear, and according to balance constants of components in each phase during balance, the equation set can be solved in a combined mode, and the balance mole components of each gas-liquid-solid phase can be calculated to form each phase mole;
flash evaporation calculation is carried out to determine the volume of a condensate gas sample under the saturation pressure, and the volume at the moment is the volume of a constant volume。
6. The method for dynamically predicting the waxy phase state of a condensate gas reservoir in constant volume failure according to claim 1, wherein the constant volume failure is calculated to obtain the mole fraction and the composition of each phase, and the volume of each phase under the current failure pressure is calculated to reduce the volume of the gas phaseThe remaining phase volumes remain unchanged and the fluid composition after venting is calculated from the new phase fractions.
7. The method for dynamically predicting the wax precipitation phase of a condensate gas reservoir in constant volume failure according to claim 1, wherein the step S5 comprises updating the temperature on the basis of a flash evaporation model until the solid phase precipitation temperature is the wax precipitation temperature under the current condition, adjusting the pressure, and repeating the process to calculate a wax precipitation curve of a flash evaporation component.
8. The method for dynamically predicting the wax phase state of a condensate gas reservoir in constant volume failure according to claim 1, wherein the step S5 comprises the steps of performing single degassing flash evaporation calculation on a liquid phase part of the residual fluid component under the failure pressure to obtain a de-aerated oil component composition, performing the wax phase state calculation, and simulating a shale condensate gas reservoir reverse condensate liquid extraction process.
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