Method for predicting drainage capacity after water breakthrough of gas well of water-driven gas reservoir and related equipment

Abstract

The invention discloses a method for predicting drainage capacity after water breakthrough of a gas well of a water-driven gas reservoir, and the method comprises the steps: obtaining a natural gas compression factor fitting formula, a natural gas viscosity fitting formula, a gas phase relative permeability fitting formula and a water phase relative permeability fitting formula based on basic parameters of the water-driven gas reservoir according to the basic parameters of the water-driven gas reservoir; the method comprises the following steps: firstly, obtaining the gas phase relative permeability of a reservoir in an original state and the water phase relative permeability of the reservoir after water drive through calculation, finally establishing a water production equation after water breakthrough of a gas well, calculating the daily water production of the gas well under different bottom hole pressures after water breakthrough of the gas well according to the water production equation after water breakthrough of the gas well, and drawing a relation curve of the daily water production after water breakthrough of the gas well and the bottom hole pressures. Firstly, the whole process has low requirements on hardware and software and is easy to implement, then the problem of drainage capacity prediction after water breakthrough of the water-driven gas reservoir gas well is solved, the relative prediction error is smaller than 20%, and technical support is provided for formulating a water-driven gas reservoir drainage gas recovery efficiency improving scheme.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas reservoir development, and particularly relates to a method for predicting the drainage capacity of a water drive gas reservoir well after water breakthrough and related equipment. Background Art

[0002] As the main gas reservoir for increasing natural gas reserves and production in China, water drive gas reservoirs generally face the problem of low reservoir recovery factor due to non-uniform water invasion and water production. Drainage gas production is an important means to improve the recovery factor of water drive gas reservoirs. Under certain conditions, the increase in drainage gas production in water drive gas reservoirs is positively correlated with the drainage volume. Currently, drainage wells mainly consist of gas wells after water breakthrough. Therefore, accurately predicting the drainage capacity of water drive gas reservoir wells after water breakthrough is crucial for formulating a drainage gas production and enhanced recovery plan in the middle and late stages of water drive gas reservoir development.

[0003] Currently, the research on drainage gas production in gas reservoirs mainly focuses on drainage gas production process technologies. Huang Yan, She Chaoyi, Zhong Xiaoyu, etc. "Current Situation and Development Trend of Drainage Gas Production Process Technology" [J]. Drilling & Production Technology, 2005(04):57-60+18. It has developed from single-well drainage gas production process technology to a multi-disciplinary gas reservoir overall water control technology that combines single-well drainage with gas reservoir engineering, and at the same time, a series of supporting research on drainage gas production process technology and equipment, and workover technology has been carried out. The article introduces the current situation, development focus and trend of drainage gas production process technology, and puts forward suggestions based on the development of existing technologies. There is a lack of a method for predicting the drainage capacity of gas wells after water breakthrough, and the drainage capacity of gas wells after water breakthrough can only be determined based on the production dynamics of water drive gas reservoir wells after water breakthrough, which affects the scientific formulation of a drainage gas production and enhanced recovery plan for water drive gas reservoirs. Summary of the Invention

[0004] The present invention provides a method for predicting the drainage capacity of a water drive gas reservoir well after water breakthrough and related equipment, which solves the problem that the drainage capacity of a gas well after water breakthrough can only be determined based on the production dynamics of a water drive gas reservoir well after water breakthrough, affecting the scientific formulation of a drainage gas production and enhanced recovery plan for water drive gas reservoirs.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for predicting the drainage capacity of a water drive gas reservoir well after water breakthrough, comprising:

[0007] Obtaining basic parameters of the water drive gas reservoir;

[0008] Calculating the gas phase relative permeability under the original state of the reservoir and the water phase relative permeability of the reservoir after water drive according to the basic parameters of the water drive gas reservoir;

[0009] Establishing a gas production equation for the gas well according to the binomial fitting result of the square difference of the gas well testing pressure and the daily gas production;

[0010] Calculate the coefficient of the water production equation after water breakthrough in a gas well based on the gas production equation of the gas well, the original gas-phase relative permeability of the reservoir, and the water-phase relative permeability of the reservoir after water flooding, and establish the water production equation after water breakthrough in the gas well;

[0011] Calculate the daily water production of the gas well under different bottom-hole pressures after water breakthrough in the gas well according to the water production equation after water breakthrough in the gas well, and draw the relationship curve between the daily water production and the bottom-hole pressure after water breakthrough in the gas well.

[0012] Preferably, the basic parameters of the water-drive gas reservoir include the original gas saturation of the reservoir, reservoir temperature, formation water viscosity, natural gas PVT data, and gas-water relative permeability data.

[0013] Preferably, calculating the original gas-phase relative permeability of the reservoir and the water-phase relative permeability of the reservoir after water flooding according to the basic parameters of the water-drive gas reservoir is specifically as follows:

[0014] Establish the fitting formulas for the gas compressibility factor and natural gas viscosity based on the basic parameters of the water-drive gas reservoir, and at the same time establish the fitting formulas for the gas-phase relative permeability and water-phase relative permeability;

[0015] Calculate the original gas-phase relative permeability of the reservoir and the water-phase relative permeability of the reservoir after water flooding according to the basic parameters of the water-drive gas reservoir, the fitting formulas for the gas compressibility factor and natural gas viscosity, and the fitting formulas for the gas-phase relative permeability and water-phase relative permeability;

[0016] The fitting formula for the gas compressibility factor is: Z = a0 + a1P + a2P 2

[0017] The fitting formula for natural gas viscosity is: μ g = b0 + b1P + b2P 2

[0018] In the formula: Z - gas compressibility factor, f; μ g - natural gas viscosity, mPa.s; P - formation pressure, MPa; a0, a1, a2, b0, b1, b2 are the corresponding fitting parameters respectively.

[0019] Preferably, the fitting formula for the gas-phase relative permeability K rg is:

[0020] The fitting formula for the water-phase relative permeability K rw is:

[0021] In the formula: K rg - gas-phase relative permeability; K rw - water-phase relative permeability; S w - water saturation; c0, c1, c2, d0, d1, d2 are the corresponding fitting parameters respectively.

[0022] Preferably, the gas-phase relative permeability under the original reservoir condition and the water-phase relative permeability of the reservoir after water flooding are calculated according to the fitting formulas of the natural gas compressibility factor, natural gas viscosity, gas-phase relative permeability, and water-phase relative permeability for the basic parameters of the water-drive gas reservoir, specifically as follows:

[0023] The gas-phase relative permeability under the original reservoir condition is calculated according to the original water saturation of the reservoir and the fitting formula of the gas-phase relative permeability; the underground water cut at different water saturations of the water-drive gas reservoir is calculated according to the fitting formulas of natural gas viscosity, gas-phase relative permeability, and water-phase relative permeability, and then the water saturation of the reservoir after water flooding is determined, and then the water-phase relative permeability of the reservoir after water flooding is determined according to the fitting formula of the water-phase relative permeability;

[0024] The formula for calculating the underground water cut is:

[0025]

[0026] In the formula: K rg - Gas-phase relative permeability; K rw - Water-phase relative permeability; μ w - Formation water viscosity; f w - Underground water cut, μg - Natural gas viscosity;

[0027] The formula for calculating the water saturation of the reservoir after water flooding is:

[0028]

[0029] In the formula: S wi - Original water saturation of the reservoir; S wf - Water saturation at the water flooding front; - Water saturation of the reservoir after water flooding.

[0030] Preferably, the gas production equation of the gas well is:

[0031]

[0032] Among them, Pw - Bottom hole pressure; qg - Gas production rate; A, B - Coefficients of the gas production equation of the gas well.

[0033] Preferably, the water production equation of the gas well after water breakthrough is:

[0034]

[0035] Expression of coefficient A1:

[0036] Expression of coefficient B1:

[0037] Where: q w - Daily water production; T sc - Standard state temperature; T - Reservoir temperature; Psc - Standard state pressure; ρ w - Formation water density; ρ sc - Natural gas density under standard state; K rgi - Gas phase relative permeability at the original state of the reservoir; K rwc - Water phase relative permeability of the reservoir after water flooding.

[0038] A system for predicting the water drainage capacity of a gas well after water breakthrough in a water - drive gas reservoir, comprising:

[0039] An acquisition module: used to acquire the basic parameters of the water - drive gas reservoir;

[0040] A first fitting formula calculation module: used to establish a fitting formula for the gas compressibility factor and natural gas viscosity based on the basic parameters of the water - drive gas reservoir;

[0041] A second fitting formula calculation module: establish a fitting formula for the gas phase relative permeability and water phase relative permeability according to the basic parameters of the water - drive gas reservoir;

[0042] A permeability calculation module: used to calculate the gas phase relative permeability at the original state of the reservoir and the water phase relative permeability of the reservoir after water flooding according to the basic parameters of the water - drive gas reservoir, the gas compressibility factor fitting formula, the natural gas viscosity fitting formula, the gas phase relative permeability fitting formula, and the water phase relative permeability fitting formula;

[0043] An equation establishment module: used to establish a gas well gas production equation based on the square difference of the gas well testing pressure and the binomial fitting result of the daily gas production;

[0044] A water production equation establishment module after water breakthrough: used to calculate the coefficients of the water production equation of the gas well after water breakthrough according to the gas well gas production equation, the gas phase relative permeability at the original state of the reservoir, the water phase relative permeability of the reservoir after water flooding, and the basic parameters of the water - drive gas reservoir, and establish the water production equation of the gas well after water breakthrough;

[0045] A curve plotting module: used to calculate the daily water production of the gas well at different bottom - hole pressures after water breakthrough according to the water production equation of the gas well after water breakthrough, and plot the relationship curve between the daily water production of the gas well after water breakthrough and the bottom - hole pressure;

[0046] An output module: used to output the gas well gas production equation, the water production equation of the gas well after water breakthrough, and the relationship curve between the daily water production of the gas well after water breakthrough and the bottom - hole pressure.

[0047] A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of a method for predicting the water drainage capacity of a gas well after water breakthrough in a water - drive gas reservoir are implemented.

[0048] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the steps of a method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir.

[0049] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir. Based on the basic parameters of the water drive gas reservoir, a fitting formula for the natural gas compression factor, a fitting formula for the natural gas viscosity, a fitting formula for the gas-phase relative permeability, and a fitting formula for the water-phase relative permeability are obtained according to the basic parameters of the water drive gas reservoir. Then, the gas-phase relative permeability under the original reservoir state and the water-phase relative permeability of the reservoir after water drive are calculated. Finally, a water production equation after water breakthrough of the gas well is established, and the daily water production of the gas well at different bottom hole pressures after water breakthrough of the gas well is calculated according to the water production equation after water breakthrough of the gas well, and a relationship curve between the daily water production of the gas well after water breakthrough and the bottom hole pressure is drawn. First, the entire process has low requirements for hardware and software and is easy to implement. Then, it solves the problem of predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir, and the relative error of the prediction is less than 20%, providing technical support for formulating a recovery improvement plan for water drainage and gas production in a water drive gas reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a flowchart of an implementation manner of a method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir provided by the present invention.

[0051] Figure 2 is a schematic diagram of a device for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir provided by the present invention.

[0052] Figure 3 is a schematic diagram of a curve of the natural gas compression factor Z and the formation pressure P of a method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir provided by an implementation manner of the present application in a scenario example.

[0053] Figure 4 is the natural gas viscosity μ of a method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir provided by an implementation manner of the present application g and the schematic diagram of the curve of the formation pressure P.

[0054] Figure 5 is the gas-phase relative permeability K of a method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir provided by an implementation manner of the present application rg and the water saturation S w curve schematic diagram.

[0055] Figure 6 is the water-phase relative permeability K of a method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir provided by an implementation manner of the present application rwversus water saturation S w Schematic diagram.

[0056] Figure 7 is the underground water cut f of a water drive gas reservoir applying the method for predicting the drainage capacity after water breakthrough of a gas well provided by the embodiment of the present application in a scenario example w versus water saturation S w Curve schematic diagram.

[0057] Figure 8 is the square difference of the gas well testing pressure (P 2 -P w 2 ) and the daily gas production q of a gas well applying the method for predicting the drainage capacity after water breakthrough of a gas well provided by the embodiment of the present application in a scenario example g Curve schematic diagram.

[0058] Figure 9 is the schematic diagram of the gas well production IPR curve applying the method for predicting the drainage capacity after water breakthrough of a gas well provided by the embodiment of the present application in a scenario example

[0059] Figure 10 is the schematic diagram of the water production IPR curve after water breakthrough of a gas well applying the method for predicting the drainage capacity after water breakthrough of a gas well provided by the embodiment of the present application in a scenario example

[0060] Figure 11 is the schematic diagram of the system for predicting the drainage capacity after water breakthrough of a gas well in a water drive gas reservoir provided by an embodiment of the present invention Detailed implementation manners

[0061] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. The components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0062] Therefore, the detailed description of the embodiments of the present invention provided in the accompanying drawings below is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0063] It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0064] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0065] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0066] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "coupled" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0067] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0068] The present invention provides a method for predicting the water drainage capacity of a gas well after water breakthrough in a water-drive gas reservoir ( Figure 1 ), which is characterized in that the method for predicting the water drainage capacity of a gas well after water breakthrough in a water-drive gas reservoir includes the following steps ( Figure 2 ):

[0069] S11: Determine the basic parameters of the water-drive gas reservoir, including the original gas saturation S of the reservoir wi , the reservoir temperature T, the viscosity μ of the formation water w , the PVT data of natural gas (Table 1) and the gas-water relative permeability data (Table 2).

[0070] S12: Fit and establish the relationship between the gas compressibility factor Z, the viscosity μ of natural gas g and the formation pressure P, as shown in Figure 3 , Figure 4 , for subsequent calculation calls. Generally, binomial fitting is used, and the fitting correlation coefficient is greater than 0.90, meeting the requirements of subsequent calculations. The expression is as follows:

[0071] Natural gas compressibility factor Z fitting formula: Z = a0 + a1P + a2P 2 (1)

[0072] Natural gas viscosity μ g Fitting formula: μ g = b0 + b1P + b2P 2 (2)

[0073] Where: Z - natural gas compressibility factor, f; μ g - natural gas viscosity, mPa·s; P - formation pressure, MPa; a0, a1, a2, b0, b1, b2 are the corresponding fitting parameters respectively.

[0074] S13: Fit and establish the relationship between gas-phase relative permeability K rg and water-phase relative permeability K rw and water saturation S w as shown in, for example Figure 5 , Figure 6 for subsequent calculation calls. Generally, binomial fitting is used, and the fitting correlation coefficient is greater than 0.90, meeting the requirements of subsequent calculations. The expression is as follows:

[0075] Gas-phase relative permeability K rg Fitting formula:

[0076] Water-phase relative permeability K rw Fitting formula:

[0077] Where: K rg - gas-phase relative permeability, f; K rw - water-phase relative permeability, f; S w - water saturation, f; c0, c1, c2, d0, d1, d2 are the corresponding fitting parameters respectively.

[0078] S14: Calculate the gas-phase relative permeability K wi under the original reservoir condition according to the original water saturation S rg of the reservoir and the fitting formula of gas-phase relative permeability K rgi ; Calculate the underground water cut f g at different water saturations S rg of the water drive gas reservoir according to the fitting formula of natural gas viscosity μ rw in formula (2), the fitting formula of gas-phase relative permeability K w in formula (3), the fitting formula of water-phase relative permeability K w in formula (4) and formula (5), and the results are as Figure 7 shown. Determine the water saturation S w of the reservoir after water drive according to formula (6) and formula (7)., and then determine the relative permeability of the water phase in the reservoir K after water flooding according to Equation (4) rwc , and the corresponding expression is as follows:

[0079] Water cut in the reservoir: (5)

[0081] In the formula: μ w - Viscosity of formation water, mPa·s; f w - Water cut in the reservoir, f.

[0082] Water saturation in the reservoir after water flooding:

[0083] Among them:

[0084]

[0085] In the formula: S wi - Initial water saturation in the reservoir, f; S wf - Water saturation at the water flooding front, f; - Water saturation in the reservoir after water flooding, f.

[0086] S15: Establish a gas production equation for the gas well based on the binomial fitting results of the square difference of the gas well testing pressure and the daily gas production, as shown in Equations (8) and Figure 8 as shown, obtain the coefficients A and B of the gas production equation for the gas well, and calculate the daily gas production of the gas well at different bottom hole pressures according to the gas production equation of the gas well (Equation (8)), and draw the gas production IPR curve of the gas well( Figure 9 ):

[0087]

[0088] In the formula: P w - Bottom hole pressure, MPa; q g - Gas production rate, 10 4 m 3 / d; A, B - Coefficients of the gas production equation for the gas well.

[0089] S16: According to the coefficients A and B of the gas production equation of the gas well, the relative permeability of the gas phase K rgi in the reservoir under the initial state, the relative permeability of the water phase K rwc in the reservoir after water flooding, the viscosity μ w of the formation water, the viscosity μ g of the natural gas, the density ρ w of the formation water, the pressure P sc under standard conditions, the temperature T sc under standard conditions, the reservoir temperature T and the gas compressibility factor Z, calculate the coefficients A1 and B1 of the water production equation after the gas well starts to produce water, and establish the water production equation after the gas well starts to produce water. The expression is as follows:

[0090] Water production equation after water breakthrough in gas wells:

[0091] Expression of coefficient A1:

[0092] Expression of coefficient B1:

[0093] In the formula: q w - Daily water production, m 3 ; T sc - Standard state temperature, 293.15K; T - Reservoir temperature, K; Psc - Standard state pressure, 0.101325MPa; ρ w - Formation water density, Kg / m 3 ; ρ sc - Natural gas density under standard state, Kg / m 3 .; K rgi - Initial gas phase relative permeability of the reservoir, f; K rwc - Water phase relative permeability of the reservoir after water flooding, f.

[0094] S17: Calculate the daily water production of the gas well at different bottom hole pressures after water breakthrough in the gas well according to Equation (9), and draw the relationship curve between the daily water production of the gas well and the bottom hole pressure after water breakthrough in the gas well (abbreviated as the water production IPR curve after water breakthrough in the gas well, Figure 10 ).

[0095] S18: Output the gas production equation of the gas well, the water production equation after water breakthrough in the gas well, the gas production IPR curve of the gas well, and the water production IPR curve after water breakthrough in the gas well.

[0096] Table 1 Natural gas PVT data table

[0097] Formation pressure P (MPa) Natural gas compressibility factor Z (f) <![CDATA[Natural gas viscosity μ g (mPa·s)]]> 75 1.4865 0.0358 66 1.3945 0.0332 58 1.3029 0.0306 50 1.2105 0.0278 46 1.1665 0.0264 38 1.0832 0.0235 30 1.0129 0.0208 26 0.9837 0.0195 18 0.9464 0.0171

[0098] Table 2 Gas - water relative permeability data table

[0099]

[0100]

[0101] An embodiment of the present invention provides a method for predicting the drainage capacity of a gas well after water breakthrough in a water - drive gas reservoir

[0102] S11. Determine the basic parameters of the water - drive gas reservoir, including the initial gas saturation S wi of the reservoir, the reservoir temperature T, the formation water viscosity μ w , the natural gas PVT data (Table 1) and the gas - water relative permeability data (Table 2).

[0103] S12. Fit and establish the natural gas compressibility factor Z, the natural gas viscosity μ gRelationship with formation pressure P, such as Figure 3 , Figure 4 shown, for subsequent calculation calls. Generally, binomial fitting is used, and the fitting correlation coefficient is greater than 0.90, meeting the requirements of subsequent calculations. The expression is as follows:

[0104] Fitting formula for natural gas compressibility factor Z:

[0105] z = 0.828365 + 0.004849P + 0.000054P 2 (12)

[0106] Natural gas viscosity μ g Fitting formula:

[0107] μ g = 0.01063437 + 0.00034896P - 0.00000014P 2 (13)

[0108] S13. Fitting and establishing the gas-phase relative permeability K rg , water-phase relative permeability K rw and water saturation S w relationship, such as Figure 5 , Figure 6 shown, for subsequent calculation calls. Generally, binomial fitting is used, and the fitting correlation coefficient is greater than 0.90, meeting the requirements of subsequent calculations. The expression is as follows:

[0109] Gas-phase relative permeability K rg Fitting formula:

[0110]

[0111] Water-phase relative permeability K rw Fitting formula:

[0112]

[0113] S14. According to the initial water saturation S wi of the reservoir and the gas-phase relative permeability K rg fitting formula (Equation (14)), calculate the gas-phase relative permeability K rgi = 1 of the reservoir in its initial state; according to Equation (13), the natural gas viscosity μ g fitting formula, Equation (14) for the gas-phase relative permeability K rg fitting formula, Equation (15) for the water-phase relative permeability K rw fitting formula, and Equation (16) to calculate the underground water cut f w at different water saturations S w of the water drive gas reservoir. The results are as Figure 7As shown, determine the water saturation of the reservoir after water flooding according to Equations (17) and (18). Then determine the relative permeability of the water phase in the reservoir after water flooding, K, according to Equation (14). rwc = 0.3, and the corresponding expression is as follows:

[0114] Water cut in the subsurface:

[0115] Water saturation of the reservoir after water flooding:

[0116] Where:

[0117]

[0118] S15: Establish a gas production equation for the gas well based on the square difference of the gas well testing pressure and the binomial fitting result of the production rate, as shown in Equations (19) and Figure 8 shown. The coefficient A of the gas production equation for the gas well is 0.607671, and the coefficient B is 0.002076. Calculate the daily gas production of the gas well at different bottom-hole pressures according to Equation (19), and plot the gas production IPR curve of the gas well ( Figure 9 ):

[0119]

[0120] S16: According to the coefficients A and B of the gas production equation of the gas well, the relative permeability of the gas phase in the reservoir in its original state, K rgi , the relative permeability of the water phase in the reservoir after water flooding, K rwc , the viscosity of the formation water, μ w , the viscosity of the natural gas, μ g , the density of the formation water, ρ w , the pressure under standard conditions, P sc , the temperature under standard conditions, T sc 、the reservoir temperature T, and the gas compressibility factor Z, calculate the coefficients of the water production equation after the gas well starts to produce water: A1 = 0.0076; B1 = 7.9×10 -8 , and establish the water production equation after the gas well starts to produce water. The expression is as follows:

[0121] Water production equation after the gas well starts to produce water:

[0122] S17: Calculate the daily water production of the gas well at different bottom-hole pressures according to Equation (20), and plot the relationship curve between the daily water production of the gas well after it starts to produce water and the bottom-hole pressure (abbreviated as the water production IPR curve after the gas well starts to produce water, Figure 10 )

[0123] S18: Output the gas production equation of the gas well, the water production equation after the gas well starts to produce water, the gas production IPR curve of the gas well, and the water production IPR curve after the gas well starts to produce water

[0124] Another embodiment of the present invention provides a device for predicting the drainage capacity of a gas well in a water-driven gas reservoir after water is generated, wherein the device for predicting the drainage capacity of a gas well in a water-driven gas reservoir after water is generated can implement the above method, and the device for predicting the drainage capacity of a gas well in a water-driven gas reservoir after water is generated comprises:

[0125] Parameter input module, used to input reservoir temperature T and reservoir original water saturation S used by the model analysis module wi , formation water viscosity μ w , natural gas PVT data (Table 1) and gas-water relative permeability data (Table 2);

[0126] Model analysis module, used to establish the natural gas compression factor Z and natural gas viscosity μ of water drive gas reservoir g The relationship between the formation pressure P (Equation (1), Equation (2)) and the gas phase relative permeability K rg , water phase relative permeability K rw and water saturation S w Relationship (Equation (3), Equation (4)); Calculate different water saturation S w Underground water content of water-flooded gas reservoir f w , establish the underground water content f of water drive gas reservoir w and water saturation S w Relationship curve, determine the water saturation S of the reservoir after water flooding w and the corresponding water phase relative permeability K rwc ; Establish a gas production equation for the gas well according to the binomial fitting results of the square difference of the gas well test pressure and the daily gas production, and obtain the gas well gas production equation coefficients A and B; calculate the water production equation coefficients A1 and B1 of the gas well after water breakthrough according to the gas well gas production equation coefficients A and B, formula (10) and formula (11), establish the water production equation after water breakthrough of the gas well (formula (9), and calculate the daily water production of the gas well after water breakthrough under different bottom hole pressures according to formula (9), and draw the relationship curve between the daily water production of the gas well after water breakthrough and the bottom hole pressure (referred to as the water production IPR curve of the gas well after water breakthrough);

[0127] The result output module outputs the gas production equation of the gas well, the water production equation of the gas well after water breakthrough, the gas production IPR curve of the gas well and the water production IPR curve of the gas well after water breakthrough.

[0128] The beneficial effect of the present invention is that the method and the device can be used to establish a water production equation and an IPR curve of a gas well in a water-driven gas reservoir after water is generated, thereby solving the problem of predicting the drainage capacity of a gas well in a water-driven gas reservoir after water is generated.

[0129] like Figure 11 As shown, another embodiment of the present invention provides a system for predicting the drainage capacity of a gas well in a water-driven gas reservoir after water breakthrough, comprising:

[0130] Acquisition module: used to obtain basic parameters of water-drive gas reservoirs;

[0131] The first fitting formula calculation module: used to establish fitting formulas for the natural gas compressibility factor and natural gas viscosity based on the basic parameters of the water-drive gas reservoir;

[0132] The second fitting formula calculation module: establish fitting formulas for the gas-phase relative permeability and water-phase relative permeability according to the basic parameters of the water-drive gas reservoir;

[0133] The permeability calculation module: used to calculate the gas-phase relative permeability under the original reservoir state and the water-phase relative permeability of the reservoir after water drive according to the natural gas compressibility factor fitting formula, natural gas viscosity fitting formula, gas-phase relative permeability fitting formula, and water-phase relative permeability fitting formula of the basic parameters of the water-drive gas reservoir;

[0134] The equation establishment module: used to establish a gas well gas production equation based on the square difference of the gas well test gas pressure and the binomial fitting result of the daily gas production;

[0135] The water production equation establishment module after water breakthrough: used to calculate the coefficients of the water production equation after water breakthrough of the gas well and establish the water production equation after water breakthrough of the gas well according to the gas production equation of the gas well, the gas-phase relative permeability of the original reservoir state, the water-phase relative permeability of the reservoir after water drive, and the basic parameters of the water-drive gas reservoir;

[0136] The curve drawing module: used to calculate the daily water production of the gas well at different bottom hole pressures after water breakthrough of the gas well according to the water production equation after water breakthrough of the gas well, and draw the relationship curve between the daily water production of the gas well and the bottom hole pressure after water breakthrough of the gas well;

[0137] The output module: used to output the gas production equation of the gas well, the water production equation after water breakthrough of the gas well, and the relationship curve between the daily water production of the gas well and the bottom hole pressure after water breakthrough of the gas well.

[0138] The terminal device provided by an embodiment of the present invention. The terminal device of this embodiment includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps in the above-mentioned various method embodiments are implemented. Or, when the processor executes the computer program, the functions of each module / unit in the above-mentioned various device embodiments are implemented.

[0139] The computer program can be divided into one or more modules / units, and the one or more modules / units are stored in the memory and executed by the processor to complete the present invention.

[0140] The terminal device can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The terminal device may include, but is not limited to, a processor and a memory.

[0141] The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0142] The memory can be used to store the computer program and / or module. By running or executing the computer program and / or module stored in the memory, and by invoking the data stored in the memory, the processor implements various functions of the terminal device.

[0143] If the modules / units integrated in the terminal device are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, to implement all or part of the processes in the above-described embodiment methods of the present invention, it can also be completed by instructing relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-described various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0144] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Those of ordinary skill in the art, under the inspiration of the specification, can also make many forms without departing from the scope protected by the claims of the present invention, and all of these fall within the scope of protection of the present invention.

Claims

1. A method for predicting the water drainage capacity of a gas well after water breakthrough in a water-drive gas reservoir, characterized in that, Including: Obtaining basic parameters of a water-drive gas reservoir; Calculating the gas-phase relative permeability under the original reservoir state and the water-phase relative permeability of the reservoir after water drive according to the basic parameters of the water-drive gas reservoir; Establishing a gas production equation for a gas well based on the binomial fitting results of the square difference of the gas well testing pressure and the daily gas production; Calculating the coefficients of the water production equation after the gas well encounters water according to the gas production equation of the gas well, the gas-phase relative permeability under the original reservoir state, and the water-phase relative permeability of the reservoir after water drive, and establishing the water production equation after the gas well encounters water; Calculating the daily water production of the gas well under different bottom-hole pressures after the gas well encounters water according to the water production equation after the gas well encounters water, and plotting the relationship curve between the daily water production of the gas well and the bottom-hole pressure after the gas well encounters water.

2. The method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir according to claim 1, wherein The basic parameters of the water-drive gas reservoir include the original gas saturation of the reservoir, the reservoir temperature, the formation water viscosity, the natural gas PVT data, and the gas-water relative permeability data.

3. The method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir according to claim 1, wherein Specifically, calculating the gas-phase relative permeability under the original reservoir state and the water-phase relative permeability of the reservoir after water drive according to the basic parameters of the water-drive gas reservoir: Establishing a fitting formula for the natural gas compressibility factor and the natural gas viscosity based on the basic parameters of the water-drive gas reservoir, and simultaneously establishing a fitting formula for the gas-phase relative permeability and the water-phase relative permeability; Calculating the gas-phase relative permeability under the original reservoir state and the water-phase relative permeability of the reservoir after water drive according to the basic parameters of the water-drive gas reservoir, the fitting formula for the natural gas compressibility factor and the natural gas viscosity, and the fitting formula for the gas-phase relative permeability and the water-phase relative permeability; The fitting formula for the natural gas compressibility factor is: Z = a0 + a1P + a2P 2 The fitting formula for natural gas viscosity is: μ g = b0 + b1P + b2P 2 Where: Z - natural gas compressibility factor, f; μ g - natural gas viscosity, mPa·s; P - formation pressure, MPa; a0, a1, a2, b0, b1, b2 are the corresponding fitting parameters respectively.

4. A method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir according to claim 3, characterized in that Gas-phase relative permeability K rg The fitting formula is as follows: Water-phase relative permeability K rw The fitting formula is as follows: Where: K rg - gas relative permeability; K rw - water relative permeability; S w - water saturation; c0, c1, c2, d0, d1, d2 are the corresponding fitting parameters respectively.

5. A method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir according to claim 3, characterized in that, Specifically, calculating the gas-phase relative permeability under the original reservoir state and the water-phase relative permeability of the reservoir after water drive according to the fitting formula for the natural gas compressibility factor of the basic parameters of the water-drive gas reservoir, the fitting formula for the natural gas viscosity, the fitting formula for the gas-phase relative permeability, and the fitting formula for the water-phase relative permeability: Calculating the gas-phase relative permeability under the original reservoir state according to the fitting formula of the original water saturation of the reservoir and the gas-phase relative permeability; calculating the underground water cut at different water saturations of the water-drive gas reservoir according to the fitting formula of the natural gas viscosity, the fitting formula of the gas-phase relative permeability, and the fitting formula of the water-phase relative permeability, then determining the water saturation of the reservoir after water drive, and then determining the water-phase relative permeability of the reservoir after water drive according to the fitting formula of the water-phase relative permeability; The calculation formula for the underground water cut is: Where: K rg - Gas relative permeability; K rw - Water relative permeability; μ w - Formation water viscosity; f w - Underground water cut, μg - Natural gas viscosity; The calculation formula for the water saturation of the reservoir after water drive is: Where: S wi - Initial water saturation of the reservoir; S wf - Water saturation at the water flood front; - Water saturation of the reservoir after water flooding.

6. The method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir according to claim 1, characterized in that The gas production equation of the gas well is: Wherein, Pw - bottom-hole pressure; qg - gas production rate; A, B - coefficients of the gas production equation of the gas well.

7. The method for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir according to claim 1, characterized in that, The water production equation after the gas well encounters water is: Expression of coefficient A1: Expression of coefficient B1: Where: q w - Daily water production; T sc - Standard state temperature; T - Reservoir temperature; Psc - Standard state pressure; ρ w - Formation water density; ρ sc - Natural gas density under standard state; K rgi - Gas-phase relative permeability of the reservoir in its original state; K rwc - Water-phase relative permeability of the reservoir after water flooding.

8. A system for predicting the water drainage capacity of a gas well after water breakthrough in a water drive gas reservoir, characterized in that, Including: An acquisition module: used to acquire the basic parameters of the water-drive gas reservoir; A first fitting formula calculation module: used to establish a fitting formula for the natural gas compressibility factor and the natural gas viscosity based on the basic parameters of the water-drive gas reservoir; A second fitting formula calculation module: establishing a fitting formula for the gas-phase relative permeability and the water-phase relative permeability according to the basic parameters of the water-drive gas reservoir; A permeability calculation module: used to calculate the gas-phase relative permeability under the original reservoir state and the water-phase relative permeability of the reservoir after water drive according to the fitting formula of the natural gas compressibility factor of the basic parameters of the water-drive gas reservoir, the fitting formula of the natural gas viscosity, the fitting formula of the gas-phase relative permeability, and the fitting formula of the water-phase relative permeability; An equation establishment module: used to establish a gas production equation for a gas well based on the binomial fitting results of the square difference of the gas well testing pressure and the daily gas production; Water production equation establishment module after water breakthrough: It is used to calculate the coefficients of the water production equation after water breakthrough of a gas well based on the gas production equation of the gas well, the original gas-phase relative permeability of the reservoir, and the water-phase relative permeability of the reservoir after water flooding, and establish the water production equation after water breakthrough of the gas well; Curve plotting module: It is used to calculate the daily water production of the gas well at different bottom-hole pressures after water breakthrough of the gas well according to the water production equation after water breakthrough of the gas well, and plot the relationship curve between the daily water production of the gas well and the bottom-hole pressure after water breakthrough of the gas well; Output module: It is used to output the gas production equation of the gas well, the water production equation after water breakthrough of the gas well, and the relationship curve between the daily water production of the gas well and the bottom-hole pressure after water breakthrough of the gas well.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for predicting the drainage capacity of a gas well in a water-drive gas reservoir after water breakthrough as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for predicting the drainage capacity of a gas well in a water-drive gas reservoir after water breakthrough as described in any one of claims 1 to 7.

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