Gas well dynamic reserve determination method and determination system

Abstract

The embodiment of the invention provides a method and system for determining the dynamic reserves of a gas well, and belongs to the field of gas reservoir development. The determination method comprises the following steps: based on a plurality of physical property parameters of gas in a target gas well, determining a pseudo-pressure function and a pseudo-time function of the gas within a preset time period; according to the quasi-pressure function and the quasi-time function, the pressure of the gas reservoir changing along with time in a preset time period is determined; according to the time-varying pressure of the gas reservoir, the time-varying pressure of the gas reservoir under multiple variable flows is obtained, and the pressure when the flow of the last time period in the preset time period is zero is determined as the pressure after the target gas well is closed; and determining a dynamic reserve value of the target gas well according to the formation pressure of the field test of the target gas well and the theoretical pressure after the target gas well is closed. According to the method, the dynamic reserve value of the gas well can be determined when the sand body superposition phenomenon exists in the reservoir.

Description

Technical Field

[0001] The invention relates to the field of gas reservoir development, and in particular to a method and system for determining the dynamic reserves of a gas well. Background Art

[0002] In the field of gas reservoir engineering, the dynamic reserve calculation methods of lithologic gas wells mainly include well test analysis, material balance method and production instability analysis method. These methods are applicable to relatively homogeneous and well-connected closed gas reservoirs. However, for weakly connected gas reservoirs (i.e., there is a superposition of sand bodies inside the reservoir), the measured formation pressure is often greater than the true value due to the influence of energy replenishment of the peripheral sand bodies during on-site mining, so the dynamic reserves calculated by the material balance method are too large. Therefore, it is difficult to obtain the dynamic reserves of weakly connected lithologic gas reservoirs using conventional methods, and a new method to determine the dynamic reserves of such gas wells is urgently needed. Summary of the invention

[0003] The purpose of the embodiments of the present invention is to provide a method and system for determining the dynamic reserves of a gas well, which partially or completely solves the problem that conventional methods are difficult to obtain the dynamic reserves value of a weakly connected lithology gas well.

[0004] In order to achieve the above-mentioned purpose, an embodiment of the present invention provides a method for determining the dynamic reserves of a gas well, the determination method comprising: determining a pseudo-pressure function and a pseudo-time function of the gas in the target gas well within a preset time period based on a plurality of physical property parameters of the gas in the target gas well, wherein the plurality of physical property parameters include the viscosity, isothermal compressibility coefficient and deviation factor of the gas, and the daily production of the target gas well within the preset time period is fixed; determining the pressure of the gas reservoir under the target gas well within the preset time period that changes with time according to the pseudo-pressure function and the pseudo-time function of the gas, wherein the pseudo-pressure function is a function of pressure, and the pseudo-time function is a function of pressure and time; according to The pressure of the gas reservoir under the target gas well within the preset time period that changes with time is obtained, and the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates corresponding to the preset time period is obtained, wherein the variable flow rate is the daily production that changes with time within the preset time period; based on the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates corresponding to the preset time period, it is determined that the pressure when the flow rate is zero in the last time period within the preset time period is the theoretical pressure after the target gas well is closed; and the dynamic reserve value of the target gas well is determined based on the formation pressure of the target gas well in the field test and the theoretical pressure after the target gas well is closed.

[0005] Optionally, determining the pseudo-pressure function and the pseudo-time function of the gas in the target gas well within a preset time period based on multiple physical properties of the gas in the target gas well includes: determining, based on multiple physical properties of the gas in the target gas well, a function in which the viscosity of the gas in the target gas well changes with formation pressure when the daily production is fixed within a preset time period; a function in which the isothermal compressibility coefficient of the gas changes with formation pressure; and a function in which the deviation factor of the gas changes with formation pressure; and determining the pseudo-pressure function and the pseudo-time function of the gas based on the function in which the viscosity of the gas in the target gas well changes with formation pressure; the function in which the isothermal compressibility coefficient of the gas changes with formation pressure; and a function in which the deviation factor of the gas changes with formation pressure.

[0006] Optionally, based on the function μ of the viscosity of the gas in the target gas well varying with the formation pressure g (p); the isothermal compressibility of the gas as a function of the formation pressure c g (p); and the function z(p) of the deviation factor of the gas changing with the formation pressure, determining the pseudo-pressure function and the pseudo-time function of the gas includes: determining the pseudo-pressure function p of the gas by the following formula: p (p) and the pseudo-time function t a (p, t): in, μ gi represents the pressure under the original formation, z i represents the pressure deviation factor under the original formation, t represents the production time of the target gas well, φ represents the reservoir porosity, k g represents the effective permeability of gas, and the subscript i represents the parameter under the original formation pressure state.

[0007] Optionally, determining the pressure of the gas reservoir under the target gas well that changes with time within the preset time period according to the pseudo-pressure function and the pseudo-time function of the gas includes: determining the pressure of the gas reservoir under the target gas well that changes with time according to the pseudo-pressure function of the gas p (p) and the pseudo-time function t a (p, t), determine the functional relationship between the pseudo-pressure and pseudo-time of the gas p p (r,t a ), and according to the following solution conditions: p p (r, 0) = p p (p i ), Determine the pressure of the gas reservoir under the target gas well within the preset time period that changes with time:

[0008] Among them, r is the radial coordinate of any point in the gas reservoir, r erepresents the outer boundary radius of the gas reservoir under the target gas well, p i represents the initial formation pressure, q g represents the fixed daily output, a t Indicates the unit conversion constant.

[0009] Optionally, according to the time-varying pressure of the gas reservoir under the target gas well under multiple variable flow rates corresponding to the preset time period, determining the pressure when the flow rate of the last time period in the multiple variable flow rates within the preset time period is zero as the theoretical pressure after the target gas well is closed includes: determining the time-varying pressure of the gas reservoir under the target gas well under multiple variable flow rates according to the time-varying pressure of the gas reservoir under the target gas well under multiple variable flow rates and the following formula:

[0010]

[0011] Among them, r e represents the outer boundary radius of the gas reservoir under the target gas well, q j represents the flow rate of the jth time period in a preset time period (1, 2, ..., n) among multiple variable flow rates, q n Represents the flow rate of the nth time period within a preset time period (1, 2, ..., n) among multiple variable flow rates.

[0012] Optionally, determining the dynamic reserve value of the target gas well based on the formation pressure of the target gas well in the field test and the theoretical pressure after the target gas well is closed includes: when the formation pressure of the target gas well in the field test matches the theoretical pressure after the target gas well is closed, determining the utilization radius corresponding to the theoretical pressure after the target gas well is closed as the outer boundary radius of the gas reservoir under the target gas well; and determining the dynamic reserve value of the target gas well based on the utilization radius corresponding to the theoretical pressure after the target gas well is closed and the reserves determination method of the gas reservoir volume method.

[0013] On the other hand, the present invention also provides a system for determining the dynamic reserves of a gas well, the determination system comprising: a first determination module, for determining the pseudo-pressure function and the pseudo-time function of the gas in the target gas well within a preset time period based on multiple physical property parameters of the gas in the target gas well, wherein the multiple physical property parameters include the viscosity, isothermal compressibility coefficient and deviation factor of the gas, and the daily production of the target gas well within the preset time period is fixed; a second determination module, for determining the pressure of the gas reservoir under the target gas well within the preset time period that changes with time according to the pseudo-pressure function and the pseudo-time function of the gas, wherein the pseudo-pressure function is a function of pressure, and the pseudo-time function is a function of pressure and time; an acquisition module, for determining the pressure of the gas reservoir under the target gas well within the preset time period according to the pseudo-pressure function and the pseudo-time function of the gas, wherein the pseudo-pressure function is a function of pressure, and the pseudo-time function is a function of pressure and time; and According to the pressure of the gas reservoir under the target gas well within the preset time period that changes with time, the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates corresponding to the preset time period is obtained, wherein the variable flow rate is the daily production that changes with time within the preset time period; a third determination module is used to determine that the pressure when the flow rate is zero in the last time period within the preset time period is the theoretical pressure after the target gas well is closed, according to the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates corresponding to the preset time period; and a fourth determination module is used to determine the dynamic reserve value of the target gas well according to the formation pressure of the target gas well in the field test and the theoretical pressure after the target gas well is closed.

[0014] Optionally, the first determination module is used to determine the pseudo-pressure function and the pseudo-time function of the gas in the target gas well within a preset time period based on the multiple physical properties of the gas in the target gas well, including: determining, based on the multiple physical properties of the gas in the target gas well, a function of how the viscosity of the gas in the target gas well changes with the formation pressure when the daily production is fixed within a preset time period; a function of how the isothermal compressibility coefficient of the gas changes with the formation pressure; and a function of how the deviation factor of the gas changes with the formation pressure; and determining the pseudo-pressure function and the pseudo-time function of the gas based on the function of how the viscosity of the gas in the target gas well changes with the formation pressure; the function of how the isothermal compressibility coefficient of the gas changes with the formation pressure; and a function of how the deviation factor of the gas changes with the formation pressure.

[0015] Optionally, the first determination module is used to determine the viscosity of the gas in the target gas well based on the function μ of the change of the formation pressure. g (p); the isothermal compressibility of the gas as a function of the formation pressure c g (p); and the function z(p) of the deviation factor of the gas changing with the formation pressure, determining the pseudo-pressure function and the pseudo-time function of the gas includes: determining the pseudo-pressure function p of the gas by the following formula: p(p) and the pseudo-time function t a (p, t): in, μ gi represents the pressure under the original formation, z i represents the pressure deviation factor under the original formation, t represents the production time of the target gas well, φ represents the reservoir porosity, k g represents the effective permeability of gas, and the subscript i represents the parameter under the original formation pressure state.

[0016] Optionally, the second determination module is used to determine the pressure of the gas reservoir under the target gas well that changes with time within the preset time period according to the pseudo-pressure function and the pseudo-time function of the gas, including: determining the pressure of the gas reservoir under the target gas well that changes with time according to the pseudo-pressure function and the pseudo-time function of the gas according to the pseudo-pressure function of the gas. p (p) and the pseudo-time function t a (p, t), determine the functional relationship between the pseudo-pressure and pseudo-time of the gas p p (r,t a ), and according to the following solution conditions: p p (r, 0) = p p (pi), Determine the pressure of the gas reservoir under the target gas well within the preset time period that changes with time:

[0017] Among them, r is the radial coordinate of any point in the gas reservoir, r e represents the outer boundary radius of the gas reservoir under the target gas well, p i represents the initial formation pressure, q g represents the fixed daily output, a t Indicates the unit conversion constant.

[0018] Optionally, the third determination module is used to determine the pressure of the last time period in the multiple variable flow rates within the preset time period when the flow rate is zero as the theoretical pressure after the target gas well is closed, according to the pressure of the gas reservoir under the target gas well under the multiple variable flow rates corresponding to the preset time period. The method includes: determining the pressure of the gas reservoir under the target gas well under the multiple variable flow rates according to the pressure of the gas reservoir under the target gas well under the preset time period and the following formula:

[0019]

[0020] Among them, r e represents the outer boundary radius of the gas reservoir under the target gas well, q j represents the flow rate of the jth time period in a preset time period (1, 2, ..., n) among multiple variable flow rates, qn It represents the flow rate of the nth time period in the preset time period (1, 2, ..., n) among the variable flow rates.

[0021] Optionally, the fourth determination module is used to determine the dynamic reserve value of the target gas well based on the formation pressure of the target gas well in the field test and the theoretical pressure after the target gas well is closed, including: when the formation pressure of the target gas well in the field test matches the theoretical pressure after the target gas well is closed, determining the utilization radius corresponding to the theoretical pressure after the target gas well is closed as the outer boundary radius of the gas reservoir under the target gas well; and determining the dynamic reserve value of the target gas well based on the utilization radius corresponding to the theoretical pressure after the target gas well is closed and the reserve determination method of the gas reservoir volume method.

[0022] Through the above technical scheme, the embodiment of the present invention determines the pseudo-pressure function and pseudo-time function of the gas in the target gas well within a preset time period based on the physical parameters of the gas in the target gas well; uses the pseudo-pressure function and the pseudo-time function to further determine the pressure of the gas reservoir under the target gas well within the preset time period that changes with time, and obtains the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates corresponding to the preset time period, so as to further determine that the pressure when the flow rate of the last time period within the preset time period is zero is the theoretical pressure after the target gas well is closed; and then uses the formation pressure of the target gas well in the field test and the theoretical pressure after the target gas well is closed to further determine the dynamic reserve value of the target gas well. In short, through the pseudo-pressure function and the pseudo-time function, the corresponding pressure of the gas reservoir that changes with time when the daily production of the target gas well is fixed within a preset time period is determined, and the pressure of the gas reservoir that changes with time under multiple variable flow rates is further determined. The pressure of the gas reservoir that changes with time under multiple variable flow rates is used to determine the pressure of the target gas well after the well is shut in, and the dynamic reserve value of the target gas well is determined using the formation pressure of the target gas well tested on site and the theoretical pressure after the target gas well is shut down, thereby solving the problem that conventional methods are difficult to determine the dynamic reserve value of the gas well when there is sand body superposition inside the reservoir.

[0023] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0025] Figure 1 is a flow chart of a method for determining dynamic reserves of a gas well provided by an embodiment of the present invention;

[0026] Figure 2 is a flow chart of the pseudo-pressure function and the pseudo-time function provided in an embodiment of the present invention;

[0027] Figure 3 is the functional relationship of the physical property parameters fitted by the embodiment of the present invention;

[0028] Figure 4 This is a typical weakly connected lithologic gas reservoir diagram of a gas field in the East China Sea;

[0029] Figure 5 yes Figure 4 The pressure drop funnel diagram of the K9 well;

[0030] Figure 6 It is to calculate the dynamic reserve diagram using the existing gas well pressure drop method;

[0031] Figure 7 A structural diagram of a system for determining dynamic reserves of a gas well provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0033] Figure 1 The flowchart of a method for determining the dynamic reserves of a gas well provided by an embodiment of the present invention is as follows: A method for determining the dynamic reserves of a gas well, the method comprising the following steps S10-S14.

[0034] S10, based on multiple physical property parameters of the gas in the target gas well, determine the pseudo-pressure function and pseudo-time function of the gas in the target gas well within a preset time period. For details, refer to steps S101-S102.

[0035] The multiple physical property parameters include gas viscosity, isothermal compressibility coefficient and deviation factor, and the daily production of the target gas well is fixed within a preset time period.

[0036] Furthermore, if Figure 2 Shown is a flow chart of the pseudo-pressure function and pseudo-time function of the gas provided in an embodiment of the present invention.

[0037] S101. Based on multiple physical properties of the gas in the target gas well, determine a function of how the viscosity of the gas in the target gas well changes with formation pressure within a preset time period; a function of how the isothermal compressibility coefficient of the gas changes with formation pressure; and a function of how the deviation factor of the gas changes with formation pressure.

[0038] Specifically, a gas sample is first taken out from the target gas well. Based on the obtained gas sample, the gas sample is subjected to existing technical means, such as a reservoir fluid high-pressure physical property experiment, and the gas sample is tested under different pressure conditions to obtain multiple physical property parameters of the gas sample in the target gas well. Among them, the gas sample is taken from the target gas well, so the multiple physical property parameters of the gas sample represent the multiple physical property parameters of the gas in the target gas well. The gas sample can specifically be the natural gas in the gas reservoir under the target gas well, and the target gas well can specifically be a development well (i.e., an operating well). The multiple physical property parameters include but are not limited to the viscosity μ of the gas. g , isothermal compressibility c g and the deviation factor z.

[0039] Secondly, based on multiple physical parameters of the gas in the target gas well, determine the function of the viscosity of the gas in the target gas well within a preset time period as a function of the formation pressure; the function of the isothermal compressibility coefficient of the gas as a function of the formation pressure; and the function of the deviation factor of the gas as a function of the formation pressure. Among them, the preset time period can specifically be a certain period of time from the start to the end of the exploitation of the target gas well, and the unit can be days (numbers). The daily production of the target gas well within the preset time period is fixed, and the fixed daily production means that the daily gas production of the target gas well is fixed, that is, the gas production every day within the preset time period is the same.

[0040] For example, Figure 3 The present invention implements a high-pressure physical property experiment by placing the target gas in a pressure range of 0-50 MPa to obtain the viscosity, isothermal compressibility and deviation factor of the gas in the target gas well under multiple pressure conditions, thereby further determining the function μ of the viscosity of the gas in the target gas well as the formation pressure. g (p); the isothermal compressibility of the gas as a function of the formation pressure c g (p); and the function z(p) of the deviation factor of the gas changing with the formation pressure, the fitted functional relationship is specifically as follows:

[0041] μ g (p) = 0.0062*p 0.4334 ,

[0042] c g (p) = 1.7752*p -1.241 ,

[0043] z(p)=0.000214*p 2 -0.007178*p+0.983613, where p represents pressure.

[0044] S102. Determine a pseudo-pressure function and a pseudo-time function of the gas based on a function in which the viscosity of the gas in the target gas well varies with formation pressure; a function in which the isothermal compressibility coefficient of the gas varies with formation pressure; and a function in which the deviation factor of the gas varies with formation pressure.

[0045] Further, based on the function μ of the viscosity of the gas in the target gas well changing with the formation pressure g (p); the isothermal compressibility of the gas as a function of the formation pressure c g (p); and the function z(p) of the deviation factor of the gas changing with the formation pressure, determining the pseudo-pressure function and the pseudo-time function of the gas includes: determining the pseudo-pressure function p of the gas by the following formula: p (p) and the pseudo-time function t a (p, t): in, μ gi represents the pressure under the original formation, z i represents the pressure deviation factor under the original formation, t represents the production time of the target gas well, φ represents the reservoir porosity, k g represents the effective permeability of gas, and the subscript i represents the parameter under the original formation pressure state.

[0046] Specifically, in the above step S101, the function μ of the gas viscosity changing with the formation pressure is determined: g (p); isothermal compressibility of gas as a function of formation pressure c g (p); and the gas deviation factor as a function of the formation pressure change z (p), determine the gas pseudo-pressure function p p (p) and the pseudo-time function t a (p, t). In fact, the pseudo-pressure function is not the real pressure. The pseudo-pressure function is a function of pressure and a virtual pressure constructed for the convenience of engineering calculations, but it has the unit of pressure, i.e. MPa. Similarly, the pseudo-time function is not the real time. The pseudo-time function is a function of pressure and time, but it has the unit of time, i.e. day (number).

[0047] S11, determining the pressure of the gas reservoir under the target gas well that changes with time within the preset time period according to the pseudo-pressure function and the pseudo-time function of the gas, wherein the pseudo-pressure function is a function of pressure, and the pseudo-time function is a function of pressure and time.

[0048] Further, according to the pseudo-pressure function p of the gas p (p) and the pseudo-time function t a(p, t), determine the functional relationship between the pseudo-pressure and pseudo-time of the gas p p (r,t a ); According to the following solution conditions: p p (r,00=p p (pi), Determine the pressure of the gas reservoir under the target gas well within the preset time period that changes with time:

[0049]

[0050] Among them, r is the radial coordinate of any point in the gas reservoir, r e represents the outer boundary radius of the gas reservoir under the target gas well, p i represents the initial formation pressure, q g represents the fixed daily output, a t Indicates the unit conversion constant.

[0051] Specifically, according to the above steps S101-S102, the pseudo-time function p is determined. p (p) and the pseudo-time function t a (p, t), and then combined with the existing continuity equation of gas seepage: The density of a gas satisfies the following relationship: At the same time, combined with Darcy's law, the relationship corresponding to the density of the above gas is substituted into the continuity equation of gas seepage, and the control equation of gas seepage can be obtained as follows: The isothermal compressibility of a gas can be further expressed as: Applying the expression of the isothermal compressibility coefficient of gas to the right side of the governing equation of gas seepage yields: The left side of the governing equation for gas seepage can be obtained by simple deduction:

[0052] Then, the pseudo-pressure function is used to eliminate the nonlinear problem of the control equation of gas seepage, and the formula can be Written in the form of fitted pressure:

[0053] Further the formula and formula Re-introduction In the result:

[0054] Further combined with the above quasi-time function (in, ), the gas seepage control equation in the gas reservoir is obtained as: Since both the pseudo-pressure function and the pseudo-time function are pressure-related functions, the functional relationship between the pseudo-pressure and the pseudo-time can be further determined: p (r,t a ). Furthermore, the following solution conditions are set: p p (r, 0) = p p (p i ), In order to facilitate the solution, the dimensionless quantity is defined as follows: Where: α p =2×3.14×3.6×24×10 -3 , α t =3.6×24×10 -3 . This further determines the governing equation for gas seepage: The dimensionless form of is: Right now Similarly, the initial conditions can be evolved into p pD (r D , 0)=0, the inner boundary condition is The outer boundary conditions are

[0055] Finally, the governing equation for gas seepage is Initial condition p pD (rD, 0) = 0, inner boundary condition And the outer boundary conditions The control equations are formed, and the pressure of the gas reservoir under the target gas well in the preset time period (i.e., the unsteady-state seepage pressure solution of the gas reservoir under the target gas well) can be obtained by using Laplace transform (i.e., Laplace transform) and its inverse transform: The dimensionless pressure solution is then dimensionalized: the pressure of the gas reservoir under the target gas well in the preset time period that changes with time is determined as:

[0056]

[0057] The symbol p in the above formula represents the formation pressure, in MPa; i represents the initial formation pressure, in MPa, which is a known value; t represents the preset production time of the target gas well, in day; t a represents the planned production time of the target gas well, in days, which is a known value; r represents the radial coordinate of any point in the gas reservoir under the target gas well, in meters, which is a known value; r w Represents the wellbore radius of the target gas well, in meters, which is a known value; r e Indicates the outer boundary radius of the gas reservoir under the target gas well, in meters; ug Indicates gas viscosity, in centipoise cp, which is a known value; B g Represents the gas volume coefficient, which is a known value; ρ g Indicates gas density in kg / m 3 , is a known value; V g Indicates the volume of the gas in m 3 , is a known value; c g Indicates the isothermal compressibility of gas, in MPa -1 , which is a known value; z represents the deviation factor of the gas, which is a known value; v g represents the flow velocity of gas, in m / s, which is a known value; k represents the permeability of the gas reservoir, in mD, which is a known value; h represents the thickness of the gas reservoir, in meters, which is a known value; φ represents the porosity of the gas reservoir, which is a known value; S gi represents the original gas saturation of the gas reservoir, which is a known value; η represents the formation pressure conductivity, with the unit of mD*MPa / cp, which is a known value. Among them: the subscript containing sc represents the parameters obtained under standard conditions, the subscript i represents the parameters obtained under the original formation pressure state, and the subscript D represents a dimensionless variable.

[0058] The embodiment of the present invention linearizes the nonlinear problem by determining the pseudo-pressure function and pseudo-time function of the gas, thereby determining the unsteady-state pressure solution of a target gas well at a fixed production (the daily production of the target gas well is fixed), that is, determining the pressure of the gas reservoir under the target gas well that changes with time within the preset time period.

[0059] S12. According to the pressure of the gas reservoir under the target gas well in the preset time period that varies with time, obtain the pressure of the gas reservoir under the target gas well that varies with time at multiple variable flow rates corresponding to the preset time period.

[0060] The variable flow rate is the daily production that changes with time within the preset time period. Specifically, according to the above steps, the pressure of the gas reservoir under the target gas well that changes with time within the preset time period is determined as follows: Further, the existing technical means such as Duhamel principle are used to obtain the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates. Among them, the preset time period can be a time period in the expected production period of the development well. For example, if the expected development cycle is one year, the preset time period can be any time period in this year, or the expected production cycle is one year as the preset time period, which is not limited in the embodiment of the present invention. For example, the preset time period (1, 2, ..., n) can be divided into n time periods, wherein 1 can be regarded as the starting time of the target gas well startup (including but not limited to the first day or the first 2 days, 5 days, 7 days, etc. of the time period representing the start, the embodiment of the present invention is only used for explanation, and there is no limitation on the number of days each time period contains), and n can be regarded as the nth time period after the start of the target gas well. For example, 150 days are divided into 30 time periods (that is, the preset time period can contain multiple time periods), and each time period corresponds to 5 days. It is assumed that the daily production of the target gas well is a constant in one of the preset time periods (1, 2, ..., n), but the daily production of the target gas well is different between the various time periods in the n segments (that is, the variable flow rate is the daily production that changes with time in the preset time period).

[0061] Exemplarily, for the convenience of explanation, the embodiment of the present invention sets each time period in the preset time period as 1 day. Assuming that the preset time n is 30 days, it is divided into 30 time periods, that is, 30 days. Assuming that the daily gas production on the first day is x, the daily gas production on the second day is y, ..., and the daily gas production on the thirtieth day is q, then the daily gas production of x, y, ..., q is not equal (but it does not exclude that the daily production of some days in these 30 days is the same or close, but it is changing overall). This is because according to the requirements of the on-site production task, the gas well production will often be artificially adjusted, that is, n different daily productions are obtained for production, so that it is more in line with the actual production situation. Therefore, 30 variable flow rates x, y, ..., q corresponding to the preset time period (1, 2, ..., 30) can be obtained, that is, multiple variable flow rates corresponding to the preset time period are obtained. Further, according to the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates and the following formula, the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates is determined:

[0062]

[0063] Among them, r e represents the outer boundary radius of the gas reservoir under the target gas well, q j represents the flow rate of the jth time period in a preset time period (1, 2, ..., n) among multiple variable flow rates, q n Represents the flow rate of the nth time period within a preset time period (1, 2, ..., n) among multiple variable flow rates.

[0064] Specifically, according to the pressure of the gas reservoir under the target gas well that has been determined to vary with time under multiple variable flow rates:

[0065]

[0066] And Duhamel principle, after formula transformation, the pressure of the gas reservoir under the target gas well under multiple variable flow rates corresponding to the preset time period is obtained as follows:

[0067]

[0068] The formula only contains the radius r of the outer boundary of the gas reservoir below the target gas well. e ,q j ,q n and P p (p) is an unknown parameter, and the remaining parameters are all known values.

[0069] S13, according to the time-varying pressure of the gas reservoir under the target gas well at multiple variable flow rates corresponding to the preset time periods, determining the pressure when the flow rate in the last time period is zero as the theoretical pressure after the target gas well is closed.

[0070] S14. Determine the dynamic reserve value of the target gas well according to the formation pressure of the target gas well tested on site and the theoretical pressure after the target gas well is closed.

[0071] Furthermore, when the formation pressure of the target gas well measured on-site matches the theoretical pressure after the target gas well is closed, the utilization radius corresponding to the theoretical pressure after the target gas well is closed is determined as the outer boundary radius of the gas reservoir under the target gas well; and the dynamic reserve value of the target gas well is determined based on the utilization radius corresponding to the theoretical pressure after the target gas well is closed and the reserve determination method of the gas reservoir volume method.

[0072] For example, first, the expressions of the pressure of the gas reservoir under the target gas well under multiple variable flow rates obtained by the above step S12 (still taking each time period as 1 day as an example for explanation) are given, and the outer boundary radius r of the gas reservoir under the multiple target gas wells is respectively given. e Assign 10 different values ​​(respectively r e1 、r e2 ....r e10 denoted), and assign corresponding values ​​to the 30 variable flow rates corresponding to the multiple variable flow rates in the preset time period (1, 30) according to the actual measured daily output (or experience value), that is, the corresponding values ​​to q jAssign numerical values ​​to each of them, for example, q1 = 100,000 cubic meters / day, q2 = 86,000 cubic meters / day, q3 = 90,000 cubic meters / day, ..., q 29 = 65,000 cubic meters / day; at the same time, the daily output of the last day, i.e. the 30th day, is q 30 Assigning a value of 00,000 cubic meters per day can obtain the pressure of 10 groups of target gas wells after shutting in (the last time period, i.e., the last day q 30 =0 means the target gas well is closed), and correspondingly, 10 groups of pressures after well closing are obtained. p (p)(respectively P p1 (p), P p2 (p)...P p10 (p) indicates).

[0073] Secondly, when the pressure P of 10 groups after shut-in is obtained p1 (p), P p2 (p)...P p10 When one of the shut-in pressures in (p) matches the formation pressure of the target gas well tested on site (the formation pressure measured by shut-in on site is a known value), that is, one of the 10 shut-in pressure data is approximately or completely the same as the formation pressure tested on site. p2 (p) When the formation pressure is closest to the field test, the outer boundary radius r of the gas reservoir under the corresponding target gas well e2 , and finally e2 Determined as the producing radius of the target gas well, the producing radius r e2 And the reserve determination method of the gas reservoir volume method, the dynamic reserve value of the target gas well is determined as: S gi Indicates the original gas saturation of the gas reservoir, which is a known value; B gi represents the original gas volume, which is a known value; g represents the thickness of the gas reservoir, in meters, which is a known value. The theoretical pressure after the target gas well is closed is the theoretical pressure calculated according to the technical solution of the embodiment of the present invention, which corresponds to the formation pressure (actual pressure) of the target gas well in the field test.

[0074] To further illustrate the technical effects of the method of the embodiment of the present invention, Figure 4 This is a typical weakly connected lithologic gas reservoir diagram of a gas field in the East China Sea. Among them, there are currently 4 development wells near a certain exploration well, namely K5, K3, K3S and K9 wells, all of which have encountered the P7 layer sand body and have not encountered the gas-water interface. The P7 layer is widely developed in this well area, and multiple water channels are developed inside, gradually migrating from east to west. P7a2 is partially vertically cut with the P7b sand body.

[0075] Among them, the P7b layer is mainly encountered in exploration wells and K3S wells. It is a high-quality reservoir for the main waterway with a thickness ranging from 13 to 16 m. The core samples are gravel-containing coarse sand or conglomerate. The reservoir thickness is large and the physical properties are low porosity and medium permeability. The P7a2 layer is mainly encountered in K3 wells and K9 wells. The waterway thickness is large, ranging from 17 to 20 m. It can be seen from the logging curve that the GR curve of this layer is severely toothed and the physical properties are relatively poor. It is a low-porosity and low-permeability reservoir. The P7a1 layer is only encountered in the K5 well, with a thickness of 5.6 m, low porosity and low permeability, and a small scale.

[0076] Well K3S was put into production in June 2019, with perforation layers P7a / P7b and an initial formation pressure of approximately 42.29 MPa. However, Well K9 was put into production in October 2021, with perforation layers also P7a / P7b. At the beginning of production, the static pressure was measured to be approximately 40.6 MPa, which was 1.7 MPa lower than the original formation pressure. This indicates that the sand bodies around Well K9 have most likely been slightly mobilized by Well K3S, and the sand bodies between Well K3S and Well K9 are connected. However, by calculating the pressure drop funnel during normal production of Well K3S, as shown in Figure 2, Figure 5 The figure shows the pressure drop funnel diagram of Well K9. The theoretical pressure value at Well K9 should be 37.3 MPa, which is about 3.3 MPa lower than the measured value, indicating that the two sets of sand bodies are in a weakly connected state.

[0077] So far, K3S Well has carried out 4 static pressure tests, such as Figure 6 The figure shows the dynamic reserves determined by the existing gas well pressure drop method. The dynamic reserves calculated by the pressure drop method are about 2.67 billion cubic meters, which is close to the geological reserves of the P7 layer (P7a2+P7b) of 2.72 billion cubic meters depicted by seismic inversion data, indicating that the dynamic reserves calculated by the pressure drop method of the K3S well are approximately the total reserves of the P7 layer. However, the sand body of the P7 layer is weakly connected, and the fully utilized reserves of the well are unknown.

[0078] Therefore, based on the production data, fluid high-pressure physical properties and static pressure test data of the K3S well, the dynamic reserve determination method provided by the embodiment of the present invention is used to quickly evaluate its dynamic reserves. The K3S well uses the dynamic reserve determination method provided by the embodiment of the invention to determine that the dynamic reserves in October 2020 are about 1.05 billion cubic meters, the dynamic reserves in April 2021 are about 1.15 billion cubic meters, the dynamic reserves in November 2021 are about 1.203 billion cubic meters, and the dynamic reserves calculated in May 2022 are about 1.197 billion cubic meters. Therefore, the fully utilized reserves of the K3S well are about 1.2 billion cubic meters.

[0079] Through the above technical scheme, the embodiment of the present invention determines the pseudo-pressure function and pseudo-time function of the gas when the daily production of the target gas well is fixed within a preset time period based on the physical properties of the gas in the target gas well; uses the pseudo-pressure function and the pseudo-time function to further determine the pressure of the gas reservoir under the target gas well that changes with time within the preset time period, and obtains the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates, so as to further determine the pressure when the flow rate of the last day of the multiple variable flow rates within the preset time period is zero as the theoretical pressure after the target gas well is closed; and then uses the formation pressure of the target gas well tested on site and the theoretical pressure after the target gas well is closed to further determine the dynamic reserve value of the target gas well. Through the pseudo-pressure function and the pseudo-time function, the pressure of the gas reservoir that changes with time when the daily production of the target gas well is fixed within a preset time period is determined, and the pressure of the gas reservoir that changes with time under multiple variable flow rates is further determined. The pressure of the gas reservoir that changes with time under multiple variable flow rates is used to determine the pressure of the target gas well after the well is shut in. The dynamic reserve value of the target gas well is determined using the formation pressure of the target gas well tested on site and the theoretical pressure after the target gas well is shut in, thereby solving the problem that conventional methods are difficult to determine the dynamic reserve value of the gas well when there is sand body superposition inside the reservoir.

[0080] On the other hand, Figure 7The present invention also provides a structural diagram of a determination system for dynamic reserves of gas wells. The determination system includes: a first determination module 1, for determining the pseudo-pressure function and pseudo-time function of the gas in the target gas well within a preset time period based on multiple physical property parameters of the gas in the target gas well, wherein the multiple physical property parameters include the viscosity, isothermal compressibility coefficient and deviation factor of the gas, and the daily production of the target gas well within the preset time period is fixed; a second determination module 2, for determining the pressure of the gas reservoir under the target gas well within the preset time period according to the pseudo-pressure function and pseudo-time function of the gas, wherein the pseudo-pressure function is a function of pressure, and the pseudo-time function is a function of pressure and time; an acquisition module 3, for determining the pressure of the gas reservoir under the target gas well within the preset time period according to the pseudo-pressure function and pseudo-time function of the gas, wherein the pseudo-pressure function is a function of pressure, and the pseudo-time function is a function of pressure and time; and The pressure that changes with time is used to obtain the pressure that changes with time in the gas reservoir under the target gas well under multiple variable flow rates, wherein the variable flow rate is the daily production that changes with time within the preset time period; a third determination module 4 is used to determine, based on the pressure that changes with time in the gas reservoir under the target gas well under multiple variable flow rates corresponding to the preset time period, the pressure when the flow rate of the last time period in the multiple variable flow rates within the preset time period is zero as the theoretical pressure after the target gas well is closed, wherein the multiple variable flow rates are the daily production that changes with time within the preset time period; and a fourth determination module 5 is used to determine the dynamic reserve value of the target gas well based on the formation pressure of the target gas well in the field test and the theoretical pressure after the target gas well is closed.

[0081] The principle and effect of the system for determining the dynamic reserves of a gas well provided in the embodiment of the present invention are the same as those in the above embodiment and will not be described in detail here.

[0082] Preferably, the first determination module 1 is used to determine the pseudo-pressure function and the pseudo-time function of the gas in the target gas well within a preset time period based on the multiple physical properties of the gas in the target gas well, including: determining, based on the multiple physical properties of the gas in the target gas well, a function of how the viscosity of the gas in the target gas well changes with the formation pressure when the daily production is fixed within a preset time period; a function of how the isothermal compressibility coefficient of the gas changes with the formation pressure; and a function of how the deviation factor of the gas changes with the formation pressure; and determining the pseudo-pressure function and the pseudo-time function of the gas based on the function of how the viscosity of the gas in the target gas well changes with the formation pressure; the function of how the isothermal compressibility coefficient of the gas changes with the formation pressure; and a function of how the deviation factor of the gas changes with the formation pressure.

[0083] Preferably, the first determination module 1 is used to determine the viscosity of the gas in the target gas well based on the function μ of the change of the formation pressure. g (p); the isothermal compressibility of the gas as a function of the formation pressure cg (p); and the function z(p) of the deviation factor of the gas changing with the formation pressure, determining the pseudo-pressure function and the pseudo-time function of the gas includes: determining the pseudo-pressure function p of the gas by the following formula: p (p) and the pseudo-time function t a (p, t): in, μ gi represents the pressure under the original formation, z i represents the pressure deviation factor under the original formation, t represents the production time of the target gas well, φ represents the reservoir porosity, k g represents the effective permeability of gas, and the subscript i represents the parameter under the original formation pressure state.

[0084] The method and effect of the pseudo-pressure function and pseudo-time function of the gas provided in the embodiment of the present invention are the same as those in the above embodiment and will not be described in detail here.

[0085] Preferably, the second determination module is used to determine the pressure of the gas reservoir under the target gas well that changes with time within the preset time period according to the pseudo-pressure function and the pseudo-time function of the gas, including: determining the pressure of the gas reservoir under the target gas well that changes with time according to the pseudo-pressure function and the pseudo-time function of the gas according to the pseudo-pressure function of the gas. p (p) and the pseudo-time function t a (p, t), determine the functional relationship between the pseudo-pressure and pseudo-time of the gas p p (r,t a ), and according to the following solution conditions: p p (r, 0) = p p (p, i), Determine the pressure of the gas reservoir under the target gas well within the preset time period that changes with time: Among them, r is the radial coordinate of any point in the gas reservoir, r g represents the outer boundary radius of the gas reservoir under the target gas well, p i represents the initial formation pressure, q g represents the fixed daily output, a t Indicates the unit conversion constant.

[0086] Preferably, the third determination module 4 is used to obtain the pressure of the gas reservoir under the target gas well that varies with time under multiple variable flow rates according to the pressure of the gas reservoir under the target gas well that varies with time under multiple variable flow rates within the preset time period, and determine the pressure when the flow rate on the last day of the multiple variable flow rates within the preset time period is zero as the theoretical pressure after the target gas well is closed, including: determining the pressure of the gas reservoir under the target gas well that varies with time under multiple variable flow rates according to the following formula:

[0087]

[0088] Among them, r e represents the outer boundary radius of the gas reservoir under the target gas well, q j represents the flow rate of the jth time period in a preset time period (1, 2, ..., n) among multiple variable flow rates, q n Represents the flow rate of the nth time period within a preset time period (1, 2, ..., n) among multiple variable flow rates.

[0089] Preferably, the fourth determination module 5 is used to determine the dynamic reserve value of the target gas well according to the formation pressure of the target gas well tested on site and the theoretical pressure after the target gas well is closed, including: when the formation pressure of the target gas well tested on site matches the theoretical pressure after the target gas well is closed, determining the producing radius corresponding to the theoretical pressure after the target gas well is closed as the outer boundary radius r of the gas reservoir under the target gas well. e ; and determining the dynamic reserve value of the target gas well according to the producing radius corresponding to the theoretical pressure after the target gas well is closed and the reserve determination method of the gas reservoir volume method.

[0090] The method and effect of determining the dynamic reserve value of the target gas well provided in the embodiment of the present invention are the same as those in the above embodiment and will not be described in detail here.

[0091] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0092] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for determining the dynamic reserves of a gas well, characterized in that: The determination method comprises: Based on multiple physical property parameters of the gas in the target gas well, determine the pseudo-pressure function and the pseudo-time function of the gas in the target gas well within a preset time period, wherein the multiple physical property parameters include the viscosity, isothermal compressibility coefficient and deviation factor of the gas, and the daily production of the target gas well within the preset time period is fixed; Determine the pressure of the gas reservoir under the target gas well that changes with time within the preset time period according to the pseudo-pressure function and the pseudo-time function of the gas, wherein the pseudo-pressure function is a function of pressure, and the pseudo-time function is a function of pressure and time; According to the pressure of the gas reservoir under the target gas well in the preset time period that changes with time, obtaining the pressure of the gas reservoir under the target gas well that changes with time at multiple variable flow rates corresponding to the preset time period, wherein the variable flow rate is the daily production that changes with time in the preset time period; According to the time-varying pressure of the gas reservoir under the target gas well at multiple variable flow rates corresponding to the preset time period, determining the pressure when the flow rate is zero in the last time period within the preset time period as the theoretical pressure after the target gas well is closed; and The dynamic reserve value of the target gas well is determined according to the formation pressure of the target gas well tested on site and the theoretical pressure after the target gas well is closed.

2. The determination method according to claim 1, characterized in that: The step of determining the pseudo-pressure function and the pseudo-time function of the gas in the target gas well within a preset time period based on multiple physical property parameters of the gas in the target gas well includes: Based on multiple physical parameters of the gas in the target gas well, determine a function of the viscosity of the gas in the target gas well when the daily production is fixed within a preset time period and the formation pressure; a function of the isothermal compressibility coefficient of the gas and the formation pressure; and a function of the deviation factor of the gas and the formation pressure; and Based on the function of the viscosity of the gas in the target gas well changing with the formation pressure; the function of the isothermal compressibility coefficient of the gas changing with the formation pressure; and the function of the deviation factor of the gas changing with the formation pressure, the pseudo-pressure function and the pseudo-time function of the gas are determined.

3. The determination method according to claim 2, characterized in that: Based on the function μ of the viscosity of the gas in the target gas well changing with the formation pressure g (p); the isothermal compressibility of the gas as a function of the formation pressure c g (p); and a function z(p) of the deviation factor of the gas changing with the formation pressure, and determining the pseudo-pressure function and the pseudo-time function of the gas comprises: The pseudo-pressure function p of the gas is determined by the following formula: p (p) and the pseudo-time function t a (p, t): in, μ gi represents the pressure under the original formation, z i represents the pressure deviation factor under the original formation, t represents the production time of the target gas well, φ represents the reservoir porosity, k g represents the effective permeability of gas, and the subscript i represents the parameter under the original formation pressure state.

4. The determination method according to claim 3, characterized in that: Determining the pressure of the gas reservoir under the target gas well that changes with time within the preset time period according to the pseudo-pressure function and the pseudo-time function of the gas includes: According to the pseudo-pressure function p of the gas p (p) and the pseudo-time function t a (p, t), determine the functional relationship between the pseudo-pressure and pseudo-time of the gas p p (r,t a ),as well as According to the following solution conditions: Determine the pressure of the gas reservoir under the target gas well in the preset time period that changes with time: Among them, r is the radial coordinate of any point in the gas reservoir, r e represents the outer boundary radius of the gas reservoir under the target gas well, p i represents the initial formation pressure, q g represents the fixed daily output, a t Indicates the unit conversion constant.

5. The determination method according to claim 4, characterized in that: According to the pressure of the gas reservoir under the target gas well that changes with time at multiple variable flow rates corresponding to the preset time period, determining the pressure when the flow rate of the last time period in the preset time period is zero as the theoretical pressure after the target gas well is closed includes: The pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates is determined according to the pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates and the following formula: Among them, r e represents the outer boundary radius of the gas reservoir under the target gas well, q j represents the flow rate of the jth time period in a preset time period (1, 2, ..., n) among multiple variable flow rates, q n Represents the flow rate of the nth time period within a preset time period (1, 2, ..., n) among multiple variable flow rates.

6. The determination method according to claim 5, characterized in that: Determining the dynamic reserve value of the target gas well according to the formation pressure of the target gas well tested on site and the theoretical pressure after the target gas well is closed includes: In the case where the formation pressure of the target gas well measured on site matches the theoretical pressure after the target gas well is closed, determining the producing radius corresponding to the theoretical pressure after the target gas well is closed as the outer boundary radius of the gas reservoir under the target gas well; and The dynamic reserve value of the target gas well is determined according to the producing radius corresponding to the theoretical pressure after the target gas well is closed and the reserve determination method of the gas reservoir volume method.

7. A system for determining dynamic reserves of a gas well, characterized in that: The determination system comprises: A first determination module is used to determine a pseudo-pressure function and a pseudo-time function of the gas in the target gas well within a preset time period based on a plurality of physical property parameters of the gas in the target gas well, wherein the plurality of physical property parameters include viscosity, isothermal compressibility coefficient and deviation factor of the gas, and a fixed daily production of the target gas well within the preset time period; A second determination module is used to determine the pressure of the gas reservoir under the target gas well that changes with time within the preset time period according to the pseudo-pressure function and the pseudo-time function of the gas, wherein the pseudo-pressure function is a function of pressure, and the pseudo-time function is a function of pressure and time; An acquisition module, configured to acquire the pressure of the gas reservoir under the target gas well that varies with time under a plurality of variable flow rates corresponding to the preset time period according to the pressure of the gas reservoir under the target gas well that varies with time within the preset time period, wherein the variable flow rate is the daily production that varies with time within the preset time period; A third determination module is used to determine the pressure when the flow rate is zero in the last time period within the preset time period as the theoretical pressure after the target gas well is closed, based on the pressure of the gas reservoir under the target gas well that changes with time at multiple variable flow rates corresponding to the preset time period; and The fourth determination module is used to determine the dynamic reserve value of the target gas well according to the formation pressure of the target gas well tested on site and the theoretical pressure after the target gas well is closed.

8. The determination system according to claim 7, characterized in that: The first determination module, which is used to determine the pseudo-pressure function and the pseudo-time function of the gas in the target gas well within a preset time period based on the multiple physical property parameters of the gas in the target gas well, includes: Based on multiple physical property parameters of the gas in the target gas well, determine a function of the viscosity of the gas in the target gas well when the daily production is fixed within a preset time period and the formation pressure; a function of the isothermal compressibility coefficient of the gas and the formation pressure; and a function of the deviation factor of the gas and the formation pressure; and Based on the function of the viscosity of the gas in the target gas well changing with the formation pressure; the function of the isothermal compressibility coefficient of the gas changing with the formation pressure; and the function of the deviation factor of the gas changing with the formation pressure, the pseudo-pressure function and the pseudo-time function of the gas are determined.

9. The determination system according to claim 8, characterized in that: The first determination module is used to determine the function μ based on the change of the viscosity of the gas in the target gas well with the formation pressure. g (p); the isothermal compressibility of the gas as a function of the formation pressure c g (p); and a function z(p) of the deviation factor of the gas changing with the formation pressure, and determining the pseudo-pressure function and the pseudo-time function of the gas comprises: The pseudo-pressure function p of the gas is determined by the following formula: p (p) and the pseudo-time function t a (p, t): in, μ gi represents the pressure under the original formation, z i represents the pressure deviation factor under the original formation, t represents the production time of the target gas well, φ represents the reservoir porosity, k g represents the effective permeability of gas, and the subscript i represents the parameter under the original formation pressure state.

10. The determination system according to claim 9, characterized in that The second determination module is used to determine the pressure of the gas reservoir under the target gas well that changes with time within the preset time period according to the pseudo-pressure function and the pseudo-time function of the gas, including: According to the pseudo-pressure function p of the gas p (p) and the pseudo-time function t a (p, t), determine the functional relationship between the pseudo-pressure and pseudo-time of the gas p p (r,t a ),as well as According to the following solution conditions: p p (r,0)=p p (p i ), Determine the pressure of the gas reservoir under the target gas well in the preset time period that changes with time: Among them, r is the radial coordinate of any point in the gas reservoir, r e represents the outer boundary radius of the gas reservoir under the target gas well, p i represents the initial formation pressure, q g represents the fixed daily output, a t Indicates the unit conversion constant.

11. The determination system according to claim 10, characterized in that: The third determination module is used to determine the pressure when the flow rate of the last time period in the preset time period is zero among the multiple variable flow rates according to the time-varying pressure of the gas reservoir under the target gas well under the multiple variable flow rates corresponding to the preset time period as the theoretical pressure after the target gas well is closed, including: The pressure of the gas reservoir under the target gas well that changes with time under multiple variable flow rates is determined according to the pressure of the gas reservoir under the target gas well that changes with time within the preset time period and the following formula: Among them, r e represents the outer boundary radius of the gas reservoir under the target gas well, q j represents the flow rate of the jth time period in a preset time period (1, 2, ..., n) among multiple variable flow rates, q n Represents the flow rate of the nth time period within a preset time period (1, 2, ..., n) among multiple variable flow rates.

12. The determination method according to claim 11, characterized in that: The fourth determination module is used to determine the dynamic reserve value of the target gas well according to the formation pressure of the target gas well tested on site and the theoretical pressure after the target gas well is closed, and includes: In the case where the formation pressure of the target gas well measured on site matches the theoretical pressure after the target gas well is closed, determining the producing radius corresponding to the theoretical pressure after the target gas well is closed as the outer boundary radius of the gas reservoir under the target gas well; and The dynamic reserve value of the target gas well is determined according to the producing radius corresponding to the theoretical pressure after the target gas well is closed and the reserve determination method of the gas reservoir volume method.

Images