A method for calculating gas action distance considering the interaction between injected gas and formation fluid

Abstract

The present invention provides a method for calculating the gas action distance taking into account the interaction between injected gas and formation fluid, and relates to the field of oil and natural gas development. Aiming at the problem that the interaction volume and action range of injected gas and formation fluid (crude oil and formation water) during reservoir gas injection is difficult to accurately predict, the present invention analyzes the dissolution effect of injected gas in formation crude oil and formation water, and combines an oil and gas reservoir engineering method to determine the volume of injected gas and formation fluid involved in dissolution, and uses an equivalent volume method to determine the action distance of injected gas. The method optimizes the calculation process, avoids the complexity of experiments and the calculation burden of numerical simulations, provides a more concise and efficient solution, and provides a theoretical basis for improving the accuracy and operability of gas injection schemes, especially in terms of improving oil and gas recovery rates.

Description

Technical Field

[0001] The invention belongs to the field of oil and natural gas development, and in particular relates to a gas action distance calculation method taking into account the interaction between injected gas and formation fluid. Background Art

[0002] Gas injection development in oil reservoirs is an effective way to improve oil recovery. By injecting gas, such as natural gas, carbon dioxide or air, into the formation, the viscosity of crude oil can be effectively reduced and the permeability of the reservoir can be increased. In gas injection development, the gas action distance directly affects the injection efficiency and the final recovery rate. Studying the gas action distance has important theoretical and practical significance for optimizing gas injection development strategies and improving recovery rates.

[0003] At present, Jiang Junshuai et al. have constructed a theoretical model of carbon dioxide throughput in tight oil reservoirs based on the mechanism of carbon dioxide convection and diffusion. The analytical solution of the theoretical model was obtained through the Laplace transform method, and the relationship curve between carbon dioxide concentration and injection radius was drawn. When the carbon dioxide concentration reaches a certain value, it can play a role in replacing crude oil in the reservoir matrix. It is believed that the radius corresponding to this concentration is the effective action distance of the gas (Jiang Junshuai, Liu Qingjie, Wang Jialu. Calculation method of the effective action radius of carbon dioxide throughput in tight oil reservoirs [J]. Science Technology and Engineering, 2020, 20(06): 2216-2222.); Gong Ruxiang et al. considered that part of the injected gas dissolved in the crude oil, and the undissolved part diffused to the periphery of the well, resulting in an increase in the gas saturation around the well. They used numerical simulation methods to construct grids and calculate the gas saturation of each grid at different times. They added the gas accumulation of each grid to obtain the total gas sweep volume, established a cylindrical model with hemispherical ends, and calculated the gas action distance based on the equivalent volume model (Gong Ruxiang. Calculation method of gas sweep radius of multi-element thermal fluid inhalation and exhalation [J]. Special Oil and Gas Reservoirs, 2016, 23(04): 119-122+157.); Huang Qianhui et al. combined the carbon dioxide inhalation and exhalation experiment with the nuclear magnetic resonance method, and used the T2 spectrum of the core after inhalation to reduce to the dry sample T2 spectrum as the The boundary of carbon dioxide completely entering the core and fully reacting with crude oil is obtained by analyzing the changes in the T2 spectrum of crude oil in the core under different conditions, obtaining the relationship between the carbon dioxide throughput and recovery degree and the throughput time, determining the time used for unit throughput distance of carbon dioxide injection in the core, and calculating the gas action distance based on the actual throughput time. This distance is considered to be the effective action distance (Huang Qianhui, Li Haibo, Yang Zhengming, et al., Experiment on the Action Distance of CO2 Injection in Shale (Tight) Reservoirs [J / OL]. Daqing Petroleum Geology and Development, 1-8[2024-09-16].).

[0004] In the actual gas injection development process, the reservoir structure is complex. When evaluating the gas action distance, there is a big difference between laboratory conditions and field conditions. The numerical simulation has many uncertainties. The theoretical model does not consider the interaction between the injected gas and the formation fluid. In addition, the existing evaluation methods have strong limitations. Therefore, it is necessary to establish a fast, effective and accurate gas action distance calculation method. Summary of the invention

[0005] Aiming at the problem that the interaction volume and action range of injected gas and formation fluid (crude oil and formation water) during reservoir gas injection are difficult to accurately predict, the present invention proposes a method for calculating the gas action distance that takes into account the interaction between injected gas and formation fluid; the present invention analyzes the dissolution of injected gas in formation crude oil and formation water, and determines the volume of injected gas and formation fluid involved in the dissolution through oil and gas reservoir engineering methods; uses the equivalent volume method to determine the action distance of injected gas; this method provides theoretical support for optimizing gas injection schemes, can effectively improve oil and gas recovery rates, and can be applied to fields such as carbon dioxide capture and storage.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical scheme, including the following steps:

[0007] Step S1. Obtain reservoir parameters, fluid property parameters, and injected gas parameters, such as porosity φ, reservoir thickness h, and formation crude oil density ρ o , formation water density ρ w 、Original gas-oil ratio R smi , gas-oil ratio after gas injection R sm , gas-water ratio R after gas injection sw , original gas-water ratio R swi , the solubility of injected gas in crude oil S om , solubility of injected gas in formation water S wm , injected gas volume G inj , injection gas volume coefficient B inj ;

[0008] Step S2. Considering the interaction between the injected gas and the formation oil, the part of the injected gas dissolved in the oil can be expressed as:

[0009] G so =(R sm -R smi )V oi (1.1)

[0010] Where: G so is the volume of injected gas dissolved in oil, m 3 ; R sm is the gas-oil ratio after gas injection, m 3 / m 3 ; R smi is the original gas-oil ratio, m 3 / m 3 ; V oi is the original volume of crude oil, m 3 ;

[0011] Step S3. Considering the interaction between the injected gas and the formation water, the part of the injected gas dissolved in the water can be expressed as:

[0012] G sw =(R sw -R swi )V wi (1.2)

[0013] Where: G sw is the volume of injected gas dissolved in water, m 3 ; R sw is the gas-water ratio after gas injection, m 3 / m 3 ; R swi is the original gas-water ratio, m 3 / m 3 ; V wi is the original water volume, m 3 ;

[0014] Step S4. The injected gas volume is divided into a dissolved part and a free part. The dissolved amount of the injected gas can be expressed as the part dissolved in the oil plus the part dissolved in the water:

[0015] G s =(R sm -R smi )V oi +(R sw -R swi )V wi (1.3)

[0016] Where: G s is the volume of injected gas dissolved, m 3 ;

[0017] Step S5. The free amount of injected gas can be expressed as the injected gas amount minus the dissolved amount of injected gas:

[0018] G f =G inj -G s (1.4)

[0019] Where: G f is the free volume of injected gas, m 3 ; G inj is the volume of injected gas, m 3 ;

[0020] Step S6. By the mole fraction of dissolved gas, the volume of injected gas in contact with crude oil and dissolved is obtained as:

[0021]

[0022] Where: V omT is the volume of oil that contacts and dissolves the injected gas, m 3 ; V wmT is the volume of formation water that contacts and dissolves the injected gas, m 3 ;M o is the molar molecular weight of the oil, g / mol; ρ o is the density of formation oil, g / cm 3 ;M w is the molar molecular weight of formation water, g / mol; ρ w is the density of water, g / cm 3 ; t is the mole fraction of injected gas; B inj is the volume coefficient of injected gas;

[0023] The volume of formation water that dissolves the injected gas is:

[0024]

[0025] Step S7. Factors (1.5) and (1.6) are not independent, and the volume of crude oil and formation water in contact with the injected gas cannot be directly calculated. Therefore, the concept of solubility is introduced. According to the solubility, the volume of the injected gas in contact with the crude oil and dissolved is:

[0026]

[0027] Where: S om is the solubility of injected gas in crude oil, m 3 / m 3 ; S wm is the solubility of injected gas in formation water, m 3 / m 3 ;

[0028] The volume of formation water that dissolves the injected gas is:

[0029]

[0030] Step S8. The dissolved gas mole fraction and solubility can be obtained:

[0031] The volume of crude oil that contacts and dissolves the injected gas is:

[0032]

[0033] The volume of formation water that contacts and dissolves the injected gas is:

[0034]

[0035] Step S9. Based on the contact volume between the injected gas and the oil and formation water, the formation volume within the impact range of the injected gas is obtained:

[0036]

[0037] Where: φ is porosity, %; V G is the volume of the formation within the gas influence range, m 3 ;

[0038] Based on the equivalent volume method, the formation volume can be obtained as:

[0039]

[0040] Combining equations (1.11) and (1.12) yields the final gas action distance:

[0041]

[0042] Where: R e is the final action distance of the gas, m; h is the reservoir thickness, m;

[0043] Step S10: V G Substituting into formula (1.13), we can get the gas action distance:

[0044]

[0045] As a further description of the above technical solution:

[0046] The process of step S2 is as follows:

[0047] Step S21. The gas volume of the original crude oil can be expressed as:

[0048] V goi =R smi V oi (2.1)

[0049] Where: V goi is the gas volume of the original crude oil, m 3 ;

[0050] Step S22. The gas volume of crude oil after gas injection can be expressed as:

[0051] V go =R sm V oi (2.2)

[0052] Where: V go is the gas-containing volume of crude oil after gas injection, m 3 ;

[0053] Step S23. The portion of the injected gas dissolved in the oil can be expressed as:

[0054] G so =V go -V goi (2.3)

[0055] Substituting equations (2.1) and (2.2) into equation (2.3), we can get the dissolved portion of injected gas in oil as:

[0056] G so =(R sm -R smi )V oi (1.1).

[0057] As a further description of the above technical solution:

[0058] The process of step S3 is as follows:

[0059] Step S31. The original formation water gas volume can be expressed as:

[0060] V gwi =R swi V wi (3.1)

[0061] If there is no dissolved gas in the formation water before gas injection, then R swi =0;

[0062] Where: V gwi is the gas volume of the original crude oil, m 3 ;

[0063] Step S32. The gas volume of the formation water after gas injection can be expressed as:

[0064] V gw =R sw V wi (3.2)

[0065] Step S33. The portion of injected gas dissolved in formation water can be expressed as:

[0066] G sw =V gw -V gwi (3.3)

[0067] Substituting equations (3.1) and (3.2) into equation (3.3), we can obtain the dissolved portion of injected gas in formation water as:

[0068] G sw =(R sw -R swi )V wi (1.2).

[0069] As a further description of the above technical solution:

[0070] The process of step S4 is as follows:

[0071] Step S41. The amount of dissolved gas in the injected gas can be expressed as the injected gas dissolved in the crude oil plus the injected gas dissolved in the formation water:

[0072] G s =G so +G sw (4.1)

[0073] Step S42. Substituting equations (1.1) and (1.2) into equation (4.1), the dissolved gas volume of the injected gas is obtained as:

[0074] G s =(R sm -R smi )V oi +(R sw -R swi )V wi (1.3).

[0075] As a further description of the above technical solution:

[0076] The process of step S6 is as follows:

[0077] Step S61. In the reservoir, the injected gas is dissolved in the crude oil and the formation water, so the molar fraction of the dissolved gas can be expressed as the ratio of the amount of dissolved gas substance to the amount of total substance:

[0078]

[0079] Where: t is the mole fraction of dissolved injected gas; n sm The amount of dissolved gas injected, mol; n om The amount of crude oil that contains dissolved gas, mol; n wm is the amount of substance in the formation water that dissolves the gas, mol;

[0080] Step S62. Under standard ground conditions, the amount of substances dissolved in the injected gas can be calculated by the ideal gas state equation:

[0081] PV=Zn sm RT(6.2)

[0082] Where: P is the pressure under standard conditions 0.101325MPa; V is the volume of underground dissolved injected gas m 3 ; Z is the deviation factor under ideal conditions, at this time Z = 1; R is the gas constant, which is 8.314 J / (mol·K); T is the temperature under standard conditions, 293.15 K;

[0083] Therefore, the amount of dissolved gas is:

[0084]

[0085] Step S63. The amount of substance dissolved in the crude oil injected into the gas can be obtained by the definition of the amount of substance:

[0086]

[0087] Step S64. The amount of substance in the formation water that dissolves the injected gas can be obtained by the definition of the amount of substance:

[0088]

[0089] Step S65. Substituting equations (6.3), (6.4), and (6.5) into equation (6.2) yields:

[0090] The volume of crude oil that dissolves the injected gas is:

[0091]

[0092] By transforming formula (1.5), the volume of formation water that dissolves the injected gas can be obtained as:

[0093]

[0094] As a further description of the above technical solution:

[0095] The process of step S7 is as follows:

[0096] Step S71. The solubility of the injected gas in the oil is:

[0097]

[0098] Step S72. The solubility of the injected gas in water is:

[0099]

[0100] Step S73. The volume of the dissolved portion of the injected gas is the volume of the portion of the injected gas dissolved in the crude oil plus the portion of the injected gas dissolved in the formation water. Therefore, substituting equations (7.1) and (7.2) into equation (4.1), we get:

[0101] The volume of crude oil that dissolves the injected gas is:

[0102]

[0103] The volume of formation water that dissolves the injected gas is:

[0104]

[0105] As a further description of the above technical solution:

[0106] The process of step S8 is as follows:

[0107] Step S81. Combining equation (1.5) with equation (1.7), the volume of crude oil that contacts and dissolves the injected gas is:

[0108]

[0109] Step S82. Combining equation (1.8) with equation (1.9), the volume of formation water that contacts and dissolves the injected gas is:

[0110]

[0111] Compared with the prior art, the present invention has the following beneficial effects:

[0112] The present invention proposes a method for calculating the interaction distance between injected gas and formation fluid (crude oil and formation water) through the method of oil and gas reservoir engineering, aiming to accurately calculate the amount of interaction between injected gas and formation fluid and determine the effective action distance of gas in the reservoir based on the equivalent volume principle; different from the traditional method relying on experiments or numerical simulations, the present invention systematically analyzes the dissolution characteristics of injected gas in formation fluids through theoretical analysis of gas reservoir engineering, combined with formation parameters and fluid characteristics; the method simplifies the calculation process, avoids the complexity of experiments and the calculation burden of numerical simulations, and provides a more concise and efficient solution; this calculation method provides a theoretical basis for improving the accuracy and operability of gas injection schemes, especially in improving oil and gas recovery rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0113] Figure 1 A flow chart of a method for calculating gas action distance taking into account the interaction between injected gas and formation fluid;

[0114] Figure 2 is a solubility curve of the injected gas in oil according to one embodiment of the present invention;

[0115] Figure 3 is a solubility curve of the injected gas in formation water according to one embodiment of the present invention;

[0116] Figure 4 is the gas-oil ratio after gas injection at different pressures according to one embodiment of the present invention;

[0117] Figure 5 is the gas-water ratio after gas injection at different pressures according to one embodiment of the present invention;

[0118] Figure 6 Graph 1 is the gas action distance under different pressures according to an embodiment of the present invention. DETAILED DESCRIPTION

[0119] The present invention is further described below with reference to the accompanying drawings and examples, so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, they are all protected.

[0120] Example

[0121] A method for calculating the gas action distance taking into account the interaction between the injected gas and the formation fluid. The calculation process is shown in Figure 1 , including the following steps in sequence:

[0122] Step S1. Taking the injection of carbon dioxide into a certain oil reservoir as an example, obtain the fluid property parameters and the injected gas parameters (the values ​​are shown in Table 1):

[0123] Table 1 Injected gas, fluid properties and reservoir parameters

[0124] parameter Value parameter Value Current formation pressure (MPa) 27 <![CDATA[Injected gas volume G inj (m 3 )]]> <![CDATA[3.845×10 8 ]]> Porosity φ(%) 14.5 Reservoir thickness (m) 17 <![CDATA[The density of formation water ρ w (g / cm 3 )]]> 1 <![CDATA[Crude oil density ρ o (g / cm 3 )]]> 0.775 <![CDATA[Original oil-in-place volume V oi (m 3 )]]> <![CDATA[2.243×10 6 ]]> <![CDATA[Molar mass of water M w (g / mol)]]> 18 <![CDATA[Original water-containing volume V wi (m 3 )]]> <![CDATA[9.613×10 5 ]]> <![CDATA[Molar molecular weight M of crude oil o (g / mol)]]> 243 <![CDATA[Original gas-oil ratio Rsmi (m 3 / m 3 )]]> 115 Mole fraction of dissolved injected gas t 0.5862 <![CDATA[Injection gas volume coefficient B inj > 0.74

[0125] Step S2. Considering the interaction between the injected gas and the formation oil, the part of the injected gas dissolved in the oil can be expressed as:

[0126] S21. As shown in Table 1, the original gas-oil ratio of the reservoir can be obtained, so the gas volume of the original crude oil can be expressed as:

[0127] V goi =115×2.243×10 6 =2.579×10 8 m 3

[0128] S22. Figure 4 As shown in the figure, the gas-oil ratio of the reservoir after gas injection under this pressure can be obtained, so the gas-containing volume of the crude oil after gas injection can be expressed as:

[0129] V go =185×2.243×10 6 =4.149×10 8 m 3

[0130] S23. The portion of injected gas dissolved in oil can be expressed as:

[0131] G so =4.149×10 8 -2.579×10 8 =1.57×10 8 m 3

[0132] S3. Considering the interaction between injected gas and formation water, the part of injected gas dissolved in water can be expressed as:

[0133] S31. The original formation water gas volume can be expressed as:

[0134] V gwi =0×9.613×10 5 m 3

[0135] There is no dissolved gas in the formation water before gas injection, so R swi =0.

[0136] S32. Figure 5 As shown in the figure, the gas-water ratio of the reservoir after gas injection under this pressure can be obtained, so the gas-containing volume of formation water after gas injection can be expressed as:

[0137] V gw =76×9.613×10 5 =7.306×10 7 m 3

[0138] S33. The part of injected gas dissolved in formation water can be expressed as:

[0139] G sw =7.306×10 7 -0=7.306×10 7 m 3

[0140] S4. The injected gas volume is divided into a dissolved part and a free part. The dissolved volume of the injected gas can be expressed as the part dissolved in oil plus the part dissolved in water.

[0141] S41. The amount of dissolved gas in injected gas can be expressed as the injected gas dissolved in crude oil plus the injected gas dissolved in formation water:

[0142] G s =1.57×10 8 +7.306×10 7 =2.301×10 8 m 3

[0143] S42. The amount of dissolved gas injected is:

[0144] G s =(R sm -R smi )V oi +(R sw -R swi )V wi

[0145] S5. The free amount of injected gas can be expressed as the injected gas amount minus the dissolved amount of injected gas:

[0146] G f =3.845×10 8 -2.301×10 8 =1.544×10 8 m 3

[0147] S6. The volume of injected gas in contact with and dissolved in crude oil can be obtained by the mole fraction of dissolved gas.

[0148] S61. In the reservoir, the injected gas is dissolved in the crude oil and formation water, so the molar fraction of dissolved gas can be expressed as the ratio of the amount of dissolved gas substance to the amount of total substance:

[0149]

[0150] S62. Under standard surface conditions, the amount of substances dissolved in the injected gas can be calculated using the ideal gas state equation:

[0151] PV=Zn sm RT

[0152] The amount of dissolved gas is calculated as:

[0153]

[0154] S63. The amount of substance dissolved in the crude oil injected into the gas can be obtained by the definition of the amount of substance:

[0155]

[0156] S64. The amount of substance in the formation water that dissolves the injected gas can be obtained by the definition of the amount of substance:

[0157]

[0158] S65. The volume of crude oil that dissolves the injected gas is:

[0159]

[0160] Substituting the above formula, we can get the volume of formation water that dissolves the injected gas:

[0161]

[0162] S7. Because the above two equations are not independent, the volumes of crude oil and formation water in contact with the injected gas cannot be directly calculated. Therefore, the concept of solubility is introduced to obtain the volume of the injected gas in contact with and dissolved in crude oil.

[0163] S71. The solubility of injected gas in oil is:

[0164]

[0165] S72. The solubility of injected gas in water is:

[0166]

[0167] S73. The volume of the dissolved portion of the injected gas is the portion of the injected gas dissolved in the crude oil plus the portion of the injected gas dissolved in the formation water:

[0168] The volume of crude oil that dissolves the injected gas is:

[0169]

[0170] The volume of formation water that dissolves the injected gas is:

[0171]

[0172] S8. The volume of crude oil that contacts and dissolves the injected gas can be obtained by the dissolved gas mole fraction and solubility. The solubility of the injected gas in the crude oil at this pressure is as follows: Figure 2 As shown in Figure 2, the solubility of injected gas in formation water is Figure 3 shown.

[0173] The volume of crude oil that contacts and dissolves the injected gas in S81 is:

[0174]

[0175] S82. The volume of formation water that contacts and dissolves the injected gas is:

[0176]

[0177] S9. Based on the equivalent volume method and combined with the formation volume within the gas influence range, the gas action distance can be obtained.

[0178] S91. Based on the contact volume between the injected gas and the oil and formation water, the formation volume within the impact range of the injected gas is obtained:

[0179]

[0180] S92. Based on the equivalent volume method, the formation volume can be obtained as:

[0181]

[0182] S93. and The final gas action distance can be obtained by combining:

[0183]

[0184] S10. The final gas action distance is:

[0185]

[0186] The solubility of injected gas in oil and water, gas-water ratio, and gas-oil ratio will change with different pressures, so the gas action distance will also change. The gas action distance under different pressures can be seen Figure 6 (Solubility under different pressures is shown in Table 2).

[0187] Table 2. Solubility of injected gas in oil and water at different pressures (T = 353.15K)

[0188] Pressure(MPa) <![CDATA[Solubility of injected gas in oil (m 3 / m 3 )]]> <![CDATA[Solubility of the injected gas in formation water / 10 -3 (m 3 / m 3 )]]> 5 59 1.45 10 75 3.78 15 92 4.68 20 113 5.13 25 136 7.01 30 158 8.78 35 167 9.21 40 179 9.87

[0189] The above description is not intended to be a formal limitation on the present invention. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for calculating the gas action distance taking into account the interaction between the injected gas and the formation fluid, characterized in that: The following steps are involved: Step S1. Obtain reservoir parameters, fluid property parameters, and injected gas parameters, such as porosity φ, reservoir thickness h, and formation crude oil density ρ o , formation water density ρ w 、Original gas-oil ratio R smi , Gas-oil ratio after gas injection R sm , gas-water ratio R after gas injection sw , original gas-water ratio R swi , solubility of injected gas in crude oil S om , solubility of injected gas in formation water S wm , injected gas volume G inj , injection gas volume coefficient B inj ; Step S2. Considering the interaction between the injected gas and the formation oil, the part of the injected gas dissolved in the oil can be expressed as: G so =(R sm -R smi )V oi (1.1) Where: G so is the volume of injected gas dissolved in oil, m 3 ; R sm is the gas-oil ratio after gas injection, m 3 / m 3 ; R smi is the original gas-oil ratio, m 3 / m 3 ; V oi is the original volume of crude oil, m 3 ; Step S3. Considering the interaction between the injected gas and the formation water, the part of the injected gas dissolved in the water can be expressed as: G sw =(R sw -R swi )V wi (1.2) Where: G sw is the volume of injected gas dissolved in water, m 3 ; R sw is the gas-water ratio after gas injection, m 3 / m 3 ; R swi is the original gas-water ratio, m 3 / m 3 ; V wi is the original water volume, m 3 ; Step S4. The injected gas volume is divided into a dissolved part and a free part. The dissolved amount of the injected gas can be expressed as the part dissolved in the oil plus the part dissolved in the water: G s =(R sm -R smi )V oi +(R sw -R swi )V wi (1.3) Where: G s is the volume of injected gas dissolved, m 3 ; Step S5. The free amount of injected gas can be expressed as the injected gas amount minus the dissolved amount of injected gas: G f =G inj -G s (1.4) Where: G f is the free volume of injected gas, m 3 ; G inj is the volume of injected gas, m 3 ; Step S6. By the mole fraction of dissolved gas, the volume of injected gas in contact with crude oil and dissolved is obtained as: Where: V omT is the volume of oil that contacts and dissolves the injected gas, m 3 ; V wmT is the volume of formation water that contacts and dissolves the injected gas, m 3 ; M o is the molar molecular weight of the oil, g / mol; ρ o is the density of formation oil, g / cm 3 ;M w is the molar molecular weight of formation water, g / mol; ρ w is the density of water, g / cm 3 ; t is the mole fraction of injected gas; B inj is the volume coefficient of injected gas; The volume of formation water that dissolves the injected gas is: Step S7. Factors (1.5) and (1.6) are not independent, and the volume of crude oil and formation water in contact with the injected gas cannot be directly calculated. Therefore, the concept of solubility is introduced. According to the solubility, the volume of the injected gas in contact with the crude oil and dissolved is: Where: S om is the solubility of injected gas in crude oil, m 3 / m 3 ; S wm is the solubility of injected gas in formation water, m 3 / m 3 ; The volume of formation water that dissolves the injected gas is: Step S8. The dissolved gas mole fraction and solubility can be obtained: The volume of crude oil that contacts and dissolves the injected gas is: The volume of formation water that contacts and dissolves the injected gas is: Step S9. Based on the contact volume between the injected gas and the oil and formation water, the formation volume within the impact range of the injected gas is obtained: Where: φ is porosity, %; V G is the volume of the formation within the gas influence range, m 3 ; Based on the equivalent volume method, the formation volume can be obtained as: Combining equations (1.11) and (1.12) yields the final gas action distance: Where: R e is the final action distance of the gas, m; h is the reservoir thickness, m; Step S10: V G Substituting into formula (1.13), we can get the gas action distance:

2. A method for calculating gas action distance considering the interaction between injected gas and formation fluid according to claim 1, characterized in that: The process of step S2 is as follows: Step S21. The gas volume of the original crude oil can be expressed as: V goi =R smi V oi (2.1) Where: V goi is the gas volume of the original crude oil, m 3 ; Step S22. The gas volume of crude oil after gas injection can be expressed as: V go =R sm V oi (2.2) Where: V go is the gas-containing volume of crude oil after gas injection, m 3 ; Step S23. The portion of the injected gas dissolved in the oil can be expressed as: G so =V go -V goi (2.3) Substituting equations (2.1) and (2.2) into equation (2.3), we can get the dissolved portion of injected gas in oil as: G so =(R sm -R smi )V oi (1.1)。 3. The method for calculating the gas action distance considering the interaction between the injected gas and the formation fluid according to claim 1, characterized in that: The process of step S3 is as follows: Step S31. The original formation water gas volume can be expressed as: V gwi =R swi V wi (3.1) If there is no dissolved gas in the formation water before gas injection, then R swi =0; Where: V gwi is the gas volume of the original crude oil, m 3 ; Step S32. The gas volume of the formation water after gas injection can be expressed as: V gw =R sw V wi (3.2) Step S33. The portion of injected gas dissolved in formation water can be expressed as: G sw =V gw -V gwi (3.3) Substituting equations (3.1) and (3.2) into equation (3.3), we can obtain the dissolved portion of injected gas in formation water as: G sw =(R sw -R swi )V wi (1.2)。 4. The method for calculating the gas action distance considering the interaction between the injected gas and the formation fluid according to claim 1, characterized in that: The process of step S4 is as follows: Step S41. The amount of dissolved gas in the injected gas can be expressed as the injected gas dissolved in the crude oil plus the injected gas dissolved in the formation water: G s =G so +G sw (4.1) Step S42. Substituting equations (1.1) and (1.2) into equation (4.1), the dissolved gas volume of the injected gas is obtained as: G s =(R sm -R smi )V oi +(R sw -R swi )V wi (1.3)。 5. The method for calculating the gas action distance considering the interaction between the injected gas and the formation fluid according to claim 1, characterized in that: The process of step S6 is as follows: Step S61. In the reservoir, the injected gas is dissolved in the crude oil and the formation water, so the molar fraction of the dissolved gas can be expressed as the ratio of the amount of dissolved gas substance to the amount of total substance: Where: t is the mole fraction of dissolved injected gas; n sm The amount of substance injected with gas for dissolution, mol; n om is the amount of substance in crude oil that dissolves gas, mol; n wm is the amount of substance in the formation water that dissolves the gas, mol; Step S62. Under standard ground conditions, the amount of substances dissolved in the injected gas can be calculated by the ideal gas state equation: PV=Zn sm RT(6.2) Where: P is the pressure under standard conditions 0.101325MPa; V is the volume of underground dissolved injected gas m 3 ; Z is the deviation factor under ideal conditions, at this time Z = 1; R is the gas constant, which is 8.314 J / (mol·K); T is the temperature under standard conditions, 293.15 K; Therefore, the amount of dissolved gas is: Step S63. The amount of substance dissolved in the crude oil injected into the gas can be obtained by the definition of the amount of substance: Step S64. The amount of substance in the formation water that dissolves the injected gas can be obtained by the definition of the amount of substance: Step S65. Substituting equations (6.3), (6.4), and (6.5) into equation (6.2) yields: The volume of crude oil that dissolves the injected gas is: By transforming formula (1.5), the volume of formation water that dissolves the injected gas can be obtained as:

6. The method for calculating the gas action distance considering the interaction between the injected gas and the formation fluid according to claim 4, characterized in that: The process of step S7 is as follows: Step S71. The solubility of the injected gas in the oil is: Step S72. The solubility of the injected gas in water is: Step S73. The volume of the dissolved portion of the injected gas is the volume of the portion of the injected gas dissolved in the crude oil plus the portion of the injected gas dissolved in the formation water. Therefore, substituting equations (7.1) and (7.2) into equation (4.1), we get: The volume of crude oil that dissolves the injected gas is: The volume of formation water that dissolves the injected gas is:

7. The method for calculating the gas action distance considering the interaction between the injected gas and the formation fluid according to claim 1, characterized in that: The process of step S8 is as follows: Step S81. Combining equation (1.5) with equation (1.7), the volume of crude oil that contacts and dissolves the injected gas is: Step S82. Combining equation (1.8) with equation (1.9), the volume of formation water that contacts and dissolves the injected gas is:

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