Method for calculating dynamic reserves of fractured-vuggy carbonate reservoir

Abstract

The invention provides a method for calculating the dynamic reserves of a fractured-vuggy carbonate reservoir, and the method comprises the steps: a production well of the fractured-vuggy carbonate reservoir carries out gas injection oil replacement production, and the gas injection oil replacement production comprises a natural energy development stage and a gas injection oil replacement development stage; according to the elastic energy of the natural energy development stage and the elastic energy of the gas injection oil replacement development stage, material balance equations of the natural energy development stage and the gas injection oil replacement development stage are established respectively, and then according to actual production data, PVT parameters and the material balance equations of a production well, the dynamic reservoir reserves and the water volume are comprehensively solved. According to the calculation method, based on the elastic energy of the oil reservoir, the material balance equation is established, the dynamic reserves and the water volume of the oil reservoir can be solved according to a small amount of actual production data, the calculation method is simple, the calculation result is accurate, and the calculation method is suitable for the complex fracture-vuggy carbonate reservoir, especially the reservoir containing bottom water.

Description

Technical Field

[0001] This invention belongs to the field of oil reservoir development technology, and relates to a method for calculating oil reservoir reserves, particularly a method for calculating the dynamic reserves of fractured-vuggy carbonate reservoirs. Background Technology

[0002] Fractured-vuggy carbonate reservoirs are a unique type of reservoir characterized by significant burial depth and diverse reservoir space types, including large reservoir areas, dissolution cavities, dissolution pores, and tectonic fractures. Fractured-vuggy carbonate reservoirs exhibit strong heterogeneity in fracture and vuggy development, with uneven fracture and vuggy scale development, resulting in a random and discontinuous distribution of reservoir bodies and complex oil-water relationships. The calculation of geological reserves in fractured-vuggy carbonate reservoirs is uncertain; static methods such as seismic techniques are insufficient to accurately evaluate the distribution and development of underground fractures and vuggies, making it impossible to accurately determine reserves and water body size. Therefore, effectively evaluating the dynamic reserves of such reservoirs is crucial for the subsequent deployment of development wells and the formulation of development technology policies.

[0003] Conventional methods for calculating dynamic reserves include decline analysis, production indicator curves, well test interpretation, and production instability analysis. Simultaneously, methods for calculating reservoir dynamic reserves using water injection indicator curves have been developed to address the replenishment development methods of oil and gas wells. Among dynamic reserve calculation methods, well test interpretation is widely used. For example, Lü Jing et al. proposed a well-fracture-single-cavity well test interpretation model for fractured-vuggy carbonate reservoirs, established a corresponding mathematical model, and derived a model reserve calculation formula ("Application of Well-Friction-Single-Cavity Well Test Interpretation Model in Dynamic Reserve Calculation of Fractured-Vuggy Carbonate Reservoirs," Technical Research, 2021, No. 4). However, the connectivity of fractures and cavities in real underground reservoirs is complex, and the establishment of simple fracture-vuggy combination theoretical models cannot reflect the reservoir characteristics, resulting in low applicability and limited application scope of well test interpretation methods. Methods for calculating reservoir dynamic reserves based on actual production data have better accuracy and universality. CN117725851A, CN116029223A, and CN111794740A disclose methods for calculating dynamic reservoir reserves based on production data from water-drive development processes. While water injection can effectively replenish formation energy, it also increases the oil-water interface. Furthermore, research indicates the existence of "attic oil" in the remaining oil type of fractured-vuggy carbonate reservoirs, which is difficult to utilize using water injection for energy replenishment, leading to inaccurate reservoir reserve assessments. Currently, researchers have proposed using gas injection for oil displacement as a replacement technology and have verified its feasibility in improving the recovery rate of fractured-vuggy carbonate reservoirs.

[0004] Therefore, this invention provides a method for calculating the dynamic reserves of fractured-vuggy carbonate reservoirs based on gas injection and oil displacement development technology. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the dynamic reserves of fractured-vuggy carbonate reservoirs based on gas injection for oil displacement production. The method is simple and convenient, and the calculation results are accurate, based on the production data and material balance equations of gas injection for oil displacement.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for calculating the dynamic reserves of fractured-vuggy carbonate reservoirs, the method comprising:

[0008] Gas injection for oil replacement production is carried out in production wells of fractured-vuggy carbonate reservoirs. The gas injection for oil replacement production includes a natural energy development stage and a gas injection for oil replacement development stage.

[0009] Based on the elastic energy of the natural energy development stage and the gas injection oil replacement development stage, material balance equations are established for the natural energy development stage and the gas injection oil replacement development stage, respectively. Then, based on the actual production data of the production wells, PVT parameters, and material balance equations, the dynamic reserves and reservoir water volume are comprehensively solved.

[0010] The calculation method provided by this invention is based on gas injection for oil displacement production in fractured-vuggy carbonate reservoirs. According to the elastic energy form of the reservoir, the material balance equations for different development stages are accurately established. Combined with actual production data, the dynamic reserves of the reservoir can be accurately calculated. It is applicable to complex fractured-vuggy carbonate reservoirs. The calculation method is simple and the calculation results are accurate.

[0011] To address the current challenge of extracting residual "attic oil," which is difficult due to the density of water compared to oil, water injection for oil replacement occurs from the bottom, resulting in an oil-water interface higher than the perforated section of the production well. Therefore, water injection is insufficient to achieve the goal of secondary enhanced oil recovery. Gas injection for oil replacement is more suitable for addressing specific oilfield conditions. The calculation method provided in this invention extends dynamic reserve calculation to reservoirs containing enclosed water bodies, adding reservoir fluid description terms. It characterizes the development mechanism of fractured-vuggy carbonate reservoirs under the combined action of oil, gas, and water phases. Treating reservoir water and crude oil as a single karst system, and utilizing the differences in oil, gas, and water expansion effects, combined with the established reservoir interpretation model and stage-based elastic yields, the size of the reservoir water body can be calculated, significantly increasing the applicability to various reservoir applications.

[0012] Preferably, the elastic energy in the natural energy development stage includes the elastic expansion energy of crude oil, the elastic expansion energy of water, and the elastic expansion energy of rocks.

[0013] Preferably, the material balance equation for the natural energy development stage is:

[0014] N P1 B o1 =[NB oi(C o +C f )+WB wi (C w +C f )](P i -P1)

[0015] Where N is the dynamic reservoir reserves, W is the reservoir water volume, and P i P1 is the initial reservoir pressure, P2 is the reservoir pressure after a certain production time, and N is the reservoir pressure. P1 B represents the oil production rate when the reservoir pressure reaches P1. oi B is the crude oil volume factor in the initial state of the reservoir. wi B is the water volume factor in the initial state of the reservoir. o1 C is the crude oil volume factor at reservoir pressure P1. o C is the compressibility coefficient of crude oil. f C is the rock compressibility coefficient. w The water compressibility coefficient.

[0016] In this invention, the material balance equation for the natural energy development stage combines the expansion energy of crude oil and the expansion energy of natural water bodies.

[0017] Preferably, the elastic energy in the gas injection-to-oil development stage includes the elastic expansion energy of crude oil, the elastic expansion energy of water, the elastic expansion energy of injected gas, and the elastic expansion energy of rock.

[0018] Preferably, the material balance equation for the gas injection oil substitution development stage is:

[0019] N P3 B o3 =[G inj B g2 (C g +C f )+(NN P2 B o2 (C o +C f )+(WW P2 B w2 (C w +C f (P2-P3)

[0020] Where N is the dynamic reservoir reserves, W is the reservoir water volume, P2 is the initial reservoir pressure for gas injection and oil displacement development, and P3 is the reservoir pressure after a certain production time. P2 N represents the cumulative oil production prior to the gas injection-to-oil substitution development phase. P3 W represents the oil production rate at reservoir pressure P3. P2 G represents the cumulative water production prior to the gas injection-to-oil development phase. injB is the volume of gas injected. g2 B is the gas volume coefficient at reservoir pressure P2. o2 B is the crude oil volume factor at reservoir pressure P2. o3 B is the crude oil volume factor at reservoir pressure P3. w2 C is the water volume factor when the reservoir pressure is P2. g C is the gas compressibility coefficient. f C is the rock compressibility coefficient. o C is the compressibility coefficient of crude oil. w The water compressibility coefficient.

[0021] In this invention, the material balance equation for the gas injection oil replacement development stage combines the elastic expansion energy of crude oil, the elastic expansion energy of water body, and the elastic expansion energy of injected gas to characterize the state changes of the three phases of oil, gas, and water during the gas injection oil replacement stage.

[0022] Preferably, the actual production data includes the production indicator curve of the production well, the gas injection volume, and the water production volume, and the elastic yield of the development stage is determined based on the production indicator curve.

[0023] Preferably, the PVT parameters include the compressibility coefficients of crude oil, gas, water, and rock, and the volume coefficients of crude oil, water, and gas.

[0024] Preferably, the process of comprehensively solving for the dynamic reserves and water volume of the reservoir includes:

[0025] (1) Transform the material balance equations of the natural energy development stage and the gas injection oil substitution development stage into expressions for the elastic yield M1 of the natural energy development stage and the elastic yield M2 of the gas injection oil substitution development stage, respectively.

[0026] (2) Simplify the expressions of M1 and M2 to obtain the expressions of reservoir dynamic reserves N and reservoir water volume W respectively;

[0027] (3) Substitute the actual production data and PVT parameters of the production well into the calculation to obtain the values ​​of reservoir dynamic reserves N and reservoir water volume W.

[0028] Preferably, the expression for the elastic yield M1 is:

[0029]

[0030] Where M1 is the elastic yield during the natural energy development phase, and P i P1 is the initial reservoir pressure, P2 is the reservoir pressure after a certain production time, and N is the reservoir pressure. P1 Let N be the oil production rate when the reservoir pressure reaches P1, and B be the dynamic reservoir reserves. oi B is the crude oil volume factor in the initial state of the reservoir.wi B is the water volume factor in the initial state of the reservoir. o1 C is the crude oil volume factor at reservoir pressure P1. o C is the compressibility coefficient of crude oil. f C is the rock compressibility coefficient. w The water compressibility coefficient.

[0031] Preferably, the expression for the elastic yield M2 is:

[0032]

[0033] Where M2 is the elastic yield during the gas injection oil displacement development stage, P2 is the initial reservoir pressure during gas injection oil displacement development, P3 is the reservoir pressure after a certain production time, and N... P3 G represents the oil production rate at reservoir pressure P3. inj For the injection volume, N P2 W represents the cumulative oil production prior to the gas injection-to-oil development phase. P2 B represents the cumulative water production prior to the gas injection-to-oil development phase. g2 B is the gas volume coefficient at reservoir pressure P2. o2 B is the crude oil volume factor at reservoir pressure P2. o3 B is the crude oil volume factor at reservoir pressure P3. w2 C is the water volume factor when the reservoir pressure is P2. g C is the gas compressibility coefficient. f C is the rock compressibility coefficient. o C is the compressibility coefficient of crude oil. w The water compressibility coefficient.

[0034] Preferably, the expression for the dynamic reserves N of the oil reservoir is:

[0035]

[0036] Preferably, the expression for the reservoir water volume W is:

[0037]

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The calculation method provided by this invention characterizes the development mechanism of fractured-vuggy carbonate reservoirs under the combined action of oil, gas and water. It regards reservoir water and crude oil as the same karst system. By considering the difference in expansion effects of oil, gas and water, and combining it with the established reservoir interpretation model, the size of the reservoir water body is solved based on the elastic yield of the stage. It is applicable to reservoirs with special residual oil type - attic oil in fractured-vuggy carbonate rocks, thus expanding the scope of application of reservoirs. The calculation method is simple and the calculation results are accurate. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of gas injection for oil displacement production in fractured-vuggy carbonate reservoirs provided in Example 1;

[0041] Figure 2 This is a schematic diagram of the natural energy development stage of the fractured-vuggy carbonate reservoir provided in Example 1;

[0042] Figure 3 This is a schematic diagram of the gas injection and oil displacement development stage of the fractured-vuggy carbonate reservoir provided in Example 1;

[0043] Wherein: 1-fractured carbonate rock; 2-production well; 3-oil storage tank; 4-oil reservoir crude oil; 5-reservoir water; 6-gas;

[0044] Figure 4 This is a production indicator curve diagram of the production well of the water-bearing body provided in Example 2. Detailed Implementation

[0045] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0046] Example 1

[0047] This embodiment provides a method for calculating the dynamic reserves of fractured-vuggy carbonate reservoirs, the calculation method including:

[0048] Gas injection for oil replacement production is carried out in production wells of fractured-vuggy carbonate reservoirs. The gas injection for oil replacement production includes a natural energy development stage and a gas injection for oil replacement development stage.

[0049] (1) Based on the elastic energy of the natural energy development stage and the gas injection oil substitution development stage, establish the material balance equation:

[0050] (1.1) Natural Energy Development Stage:

[0051] like Figure 1 As shown, the production well adopts the natural energy development method for production. In the natural energy development stage, the driving energy comes from the elastic expansion energy of the reservoir itself, including the elastic expansion energy of crude oil, the elastic expansion energy of water and the elastic expansion energy of rock.

[0052] The initial reservoir pressure of the production well is P i After a period of production, the reservoir pressure drops to P1. The material balance equation for the natural energy development stage is established as follows:

[0053] N P1 B o1 =[NBoi (C o +C f )+WB wi (C w +C f )](P i -P1)

[0054] Where N is the dynamic reservoir reserves, W is the reservoir water volume, and P i P1 is the initial reservoir pressure, P2 is the reservoir pressure after a certain production time, and N is the reservoir pressure. P1 B represents the oil production rate when the reservoir pressure reaches P1. oi B is the crude oil volume factor in the initial state of the reservoir. wi B is the water volume factor in the initial state of the reservoir. o1 C is the crude oil volume factor at reservoir pressure P1. o C is the compressibility coefficient of crude oil. f C is the rock compressibility coefficient. w The water compressibility coefficient.

[0055] (1.2) Gas injection for oil substitution development stage:

[0056] like Figure 2 As shown, after a period of natural energy development and production, the oil-water interface rises, water is encountered in the reservoir, and development shifts to gas injection for oil displacement. After gas injection for oil displacement, the oil-water interface declines, as... Figure 3 As shown.

[0057] During the gas injection-to-oil stage, the energy sources for reservoir development include gas elastic energy, crude oil elastic energy, water elastic energy, and rock elastic energy.

[0058] The initial reservoir pressure for gas injection and oil displacement development in a production well is P2. After a period of production, the reservoir pressure changes to P3. The material balance equation for the gas injection and oil displacement development stage is as follows:

[0059] N P3 B o3 =[G inj B g2 (C g +C f )+(NN P2 B o2 (C o +C f )+(WW P2 B w2 (C w +C f (P2-P3)

[0060] Where N is the dynamic reservoir reserves, W is the reservoir water volume, P2 is the initial reservoir pressure for gas injection and oil displacement development, and P3 is the reservoir pressure after a certain production time. P3 N represents the oil production rate at reservoir pressure P3. P2 W represents the cumulative oil production prior to the gas injection-to-oil development phase. P2 G represents the cumulative water production prior to the gas injection-to-oil development phase. inj B is the volume of gas injected. g2 B is the gas volume coefficient at reservoir pressure P2. o2 B is the crude oil volume factor at reservoir pressure P2. o3 B is the crude oil volume factor at reservoir pressure P3. w2 C is the water volume factor when the reservoir pressure is P2. g C is the gas compressibility coefficient. f C is the rock compressibility coefficient. o C is the compressibility coefficient of crude oil. w The water compressibility coefficient.

[0061] (2) Based on the material balance equation, the expressions for the elastic yield M1 in the natural energy development stage and the elastic yield M2 in the gas injection oil replacement development stage are obtained. By combining and simplifying these expressions, the expressions for the reservoir dynamic reserves N and the reservoir water volume W are obtained.

[0062] (2.1) The expression for the elastic yield M1 in the natural energy development stage is obtained by transforming the material balance equation in the natural energy development stage:

[0063]

[0064] The expression for the elastic yield M1 is transformed and simplified as follows:

[0065] M1B o1 =NB oi (C o +C f )+WB wi (C w +C f )

[0066] This leads to the relationship between reservoir dynamic reserves and reservoir water volume:

[0067]

[0068] (2.2) The material balance equation for the gas injection oil displacement development stage is transformed to obtain the expression for the elastic yield M2 of the gas injection oil displacement development stage:

[0069]

[0070] The expression for the elastic yield M2 is transformed and simplified as follows:

[0071] M2B o3 =G inj B g2 (C g +C f )+(NN P2 B o2 (C o +C f )+(WW P2 B w2 (C w +C f )

[0072] Then, the relationship between the dynamic reserves of the reservoir and the volume of water in the reservoir obtained during the natural energy development stage is as follows:

[0073]

[0074] Substituting into the above expression for elastic yield M2, we get:

[0075]

[0076] Simplifying the above equation, we obtain the expression for the dynamic reserves N of the reservoir as follows:

[0077]

[0078] Substituting the above expression for reservoir dynamic reserves into the relationship between reservoir dynamic reserves and reservoir water volume, we obtain the expression for reservoir water volume W:

[0079]

[0080] (3) Calculate the reservoir dynamic reserves N and reservoir water volume W by substituting the actual production data and PVT parameters of the production well into the expressions.

[0081] (3.1) Obtain the production indicator curve for gas injection to replace oil production in production wells, namely the relationship curve between pressure and cumulative oil production.

[0082] Based on the production indicator curve, the natural energy development stage and the gas injection oil replacement development stage of the production well are divided.

[0083] Based on the production instruction curve, determine the pressure drop and cumulative oil production at each development stage. The cumulative oil production per unit pressure drop is used as the elastic yield, i.e.:

[0084]

[0085]

[0086] Determine the elastic yield M1 for the natural energy development stage and the elastic yield M2 for the gas injection-to-oil development stage.

[0087] (3.2) Obtain the gas injection volume and the cumulative water production before the gas injection and oil replacement development stage of the production well.

[0088] (3.3) Obtain the PVT parameters of the production well.

[0089] PVT parameters include crude oil compressibility, gas compressibility, water compressibility, rock compressibility, crude oil volume factor in the initial reservoir state, water volume factor in the initial reservoir state, crude oil volume factor in the natural energy development stage, crude oil volume factor in the gas injection-to-oil development stage, water volume factor in the gas injection-to-oil development stage, and gas volume factor.

[0090] PVT parameters were obtained through PVT report analysis.

[0091] (3.4) Substitute the data obtained in (3.1)-(3.3) into the expressions for reservoir dynamic reserves N and reservoir water volume W to calculate the values ​​of reservoir dynamic reserves N and reservoir water volume W.

[0092] Example 2

[0093] This embodiment provides a method for calculating the dynamic reserves of fractured-vuggy carbonate reservoirs. Taking a production well in a water-bearing reservoir as the research object, the specific technical solution of the present invention is illustrated. The calculation method includes the following steps:

[0094] (1) Establish the material balance equations for the natural energy development stage and the gas injection oil substitution development stage.

[0095] The material balance equation for the natural energy development stage is:

[0096] N P1 B o1 =[NB oi (C o +C f )+WB wi (C w +C f )](P i -P1)

[0097] Where N is the dynamic reservoir reserves, W is the reservoir water volume, and P i P1 is the initial reservoir pressure, P2 is the reservoir pressure after a certain production time, and N is the reservoir pressure. P1 B represents the oil production rate when the reservoir pressure reaches P1. oi B is the crude oil volume factor in the initial state of the reservoir. wiB is the water volume factor in the initial state of the reservoir. o1 C is the crude oil volume factor at reservoir pressure P1. o C is the compressibility coefficient of crude oil. f C is the rock compressibility coefficient. w The water compressibility coefficient.

[0098] The material balance equation for the gas injection oil substitution stage is:

[0099] N P3 B o3 =[G inj B g2 (C g +C f )+(NN P2 B o2 (C o +C f )+(WW P2 B w2 (C w +C f (P2-P3)

[0100] Where N is the dynamic reservoir reserves, W is the reservoir water volume, P2 is the initial reservoir pressure for gas injection and oil displacement development, and P3 is the reservoir pressure after a certain production time. P2 N represents the cumulative oil production prior to the gas injection-to-oil substitution development phase. P3 W represents the oil production rate at reservoir pressure P3. P2 G represents the cumulative water production prior to the gas injection-to-oil development phase. inj B is the volume of gas injected. g2 B is the gas volume coefficient at reservoir pressure P2. o2 B is the crude oil volume factor at reservoir pressure P2. o3 B is the crude oil volume factor at reservoir pressure P3. w2 C is the water volume factor when the reservoir pressure is P2. g C is the gas compressibility coefficient. f C is the rock compressibility coefficient. o C is the compressibility coefficient of crude oil. w The water compressibility coefficient.

[0101] (2) Based on the material balance method in the development stage, the expression for the elastic yield in the development stage is obtained. After simplifying the equations, the expressions for the dynamic reserves N and the water volume W in the reservoir are obtained.

[0102] The expression for the elastic yield M1 in the natural energy development stage is obtained by transforming the material balance equation of the natural energy development stage:

[0103]

[0104] The expression for the elastic yield M2 in the gas injection oil displacement development stage is obtained by transforming the material balance equation of the gas injection oil displacement development stage:

[0105]

[0106] By combining the expressions for elastic yields M1 and M2, the expressions for reservoir dynamic reserves and reservoir water volume are derived.

[0107] The expression for dynamic oil reservoir reserves is:

[0108]

[0109] The expression for the volume of water in an oil reservoir is:

[0110]

[0111] (3) Obtain actual production data and PVT parameters of production wells, and calculate reservoir dynamic reserves and reservoir water volume.

[0112] Production indicator curve of production wells as follows Figure 4 As shown, the production indicator curve is divided into the natural energy development stage and the gas injection replacement oil development stage.

[0113] The pressure drop, P, during the natural energy development phase can be read from the production indicator curve. i -P1 is 40MPa, and the cumulative oil production is N. P1 3602.62m 3 Calculate the elastic yield M1 during the natural energy development phase:

[0114]

[0115] M1 is 90.0655m 3 / MPa.

[0116] The pressure drop during the gas injection and oil replacement development phase is read from the production indication curve, i.e., P2-P3 is 40 MPa, and the cumulative oil production is N. P3 It is 2749.22m 3 Calculate the elastic yield M2 during the gas injection oil substitution development stage:

[0117]

[0118] M2 is 68.7305m 3 / MPa.

[0119] The gas injection volume (G) in the gas injection process for oil displacement in production wells. inj 250,000m 3 .

[0120] The volume of water produced during the gas injection and oil displacement process in a production well, i.e., W P2 500m 3 .

[0121] The PVT parameters of the production wells are shown in Table 1.

[0122] Table 1

[0123] parameter numerical values <![CDATA[Crude oil compressibility factor (C o , MPa -1 )]]> 0.002 <![CDATA[Gas compressibility factor (C g , MPa -1 )]]> 0.006 <![CDATA[Compressibility coefficient of water body (C w , MPa -1 )]]> 0.0005 <![CDATA[Rock compressibility coefficient (C f , MPa -1 )]]> 0.0004 <![CDATA[Initial oil formation volume factor (B oi )]]> 2.4 <![CDATA[Initial water volume factor (B wi )]]> 1.1 <![CDATA[Crude oil volume factor (B o1 )]]> 2 <![CDATA[Crude oil volume factor (B o2 , B o3 )]]> 2.2 <![CDATA[Water volume coefficient (B w2 )]]> 1.2 <![CDATA[Gas volume factor (B g2 )]]> 2.50E-03

[0124] Substituting the elastic yield, gas injection volume, produced water volume, and PVT parameters into the expressions for reservoir dynamic reserves N and reservoir water volume W, the dynamic reserves N were calculated to be 29600 m³. 3 The reservoir water volume W is 9560 m³. 3 .

[0125] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for calculating the dynamic reserves of fractured-vuggy carbonate reservoirs, characterized in that, The calculation method includes: Gas injection for oil replacement production is carried out in production wells of fractured-vuggy carbonate reservoirs. The gas injection for oil replacement production includes a natural energy development stage and a gas injection for oil replacement development stage. Based on the elastic energy of the natural energy development stage and the gas injection oil replacement development stage, material balance equations are established for the natural energy development stage and the gas injection oil replacement development stage, respectively. Then, based on the actual production data of the production well, PVT parameters, and the material balance equations, the dynamic reserves and reservoir water volume are comprehensively solved.

2. The calculation method according to claim 1, characterized in that, The elastic energy in the natural energy development stage includes crude oil elastic expansion energy, water body elastic expansion energy, and rock elastic expansion energy. The material balance equation for the natural energy development phase is as follows: N P1 B o1 =[NB oi (C o +C f )+WB wi (C w +C f )](P i -P1) Where N is the dynamic reservoir reserves, W is the reservoir water volume, and P i P1 is the initial reservoir pressure, P2 is the reservoir pressure after a certain production time, and N is the reservoir pressure. P1 B represents the oil production rate when the reservoir pressure reaches P1. oi B is the crude oil volume factor in the initial state of the reservoir. wi B is the water volume factor in the initial state of the reservoir. o1 C is the crude oil volume factor at reservoir pressure P1. o C is the compressibility coefficient of crude oil. f C is the rock compressibility coefficient. w The water compressibility coefficient.

3. The calculation method according to claim 1 or 2, characterized in that, The elastic energy in the gas injection oil replacement development stage includes crude oil elastic expansion energy, water body elastic expansion energy, injected gas elastic expansion energy, and rock elastic expansion energy. The material balance equation for the gas injection oil substitution development stage is as follows: N P3 B o3 =[G inj B g2 (C g +C f )+(N-N P2 )B o2 (C o +C f )+(W-W P2 )B w2 (C w +C f )](P2-P3) Where N is the dynamic reservoir reserves, W is the reservoir water volume, P2 is the initial reservoir pressure for gas injection and oil displacement development, and P3 is the reservoir pressure after a certain production time. P2 N represents the cumulative oil production prior to the gas injection-to-oil substitution development phase. P3 W represents the oil production rate at reservoir pressure P3. P2 G represents the cumulative water production prior to the gas injection-to-oil development phase. inj B is the volume of gas injected. g2 B is the gas volume coefficient at reservoir pressure P2. o2 B is the crude oil volume factor at reservoir pressure P2. o3 B is the crude oil volume factor at reservoir pressure P3. w2 C is the water volume factor when the reservoir pressure is P2. g C is the gas compressibility coefficient. f C is the rock compressibility coefficient. o C is the compressibility coefficient of crude oil. w The water compressibility coefficient.

4. The calculation method according to any one of claims 1-3, characterized in that, The actual production data includes the production indicator curve of the production well, the gas injection volume, and the water production volume. The elastic yield rate of the development stage is determined based on the production indicator curve.

5. The calculation method according to any one of claims 1-4, characterized in that, The PVT parameters include the compressibility coefficients of crude oil, gas, water, and rock, as well as the volume coefficients of crude oil, water, and gas.

6. The calculation method according to any one of claims 1-5, characterized in that, The process of comprehensively solving for reservoir dynamic reserves and reservoir water volume includes: (1) Transform the material balance equations of the natural energy development stage and the gas injection oil substitution development stage into expressions for the elastic yield M1 of the natural energy development stage and the elastic yield M2 of the gas injection oil substitution development stage, respectively. (2) Simplify the expressions of M1 and M2 to obtain the expressions of reservoir dynamic reserves N and reservoir water volume W respectively; (3) Substitute the actual production data and PVT parameters of the production well into the calculation to obtain the values ​​of reservoir dynamic reserves N and reservoir water volume W.

7. The calculation method according to claim 6, characterized in that, The expression for the elastic yield M1 is: Where M1 is the elastic yield during the natural energy development phase, and P i P1 is the initial reservoir pressure, P2 is the reservoir pressure after a certain production time, and N is the reservoir pressure. P1 Let N be the oil production rate when the reservoir pressure reaches P1, and B be the dynamic reservoir reserves. oi B is the crude oil volume factor in the initial state of the reservoir. wi B is the water volume factor in the initial state of the reservoir. o1 C is the crude oil volume factor at reservoir pressure P1. o C is the compressibility coefficient of crude oil. f C is the rock compressibility coefficient. w The water compressibility coefficient.

8. The calculation method according to claim 6 or 7, characterized in that, The expression for the elastic yield M2 is: Where M2 is the elastic yield during the gas injection oil displacement development stage, P2 is the initial reservoir pressure during gas injection oil displacement development, P3 is the reservoir pressure after a certain production time, and N... P3 G represents the oil production rate at reservoir pressure P3. inj For the injection volume, N P2 W represents the cumulative oil production prior to the gas injection-to-oil development phase. P2 B represents the cumulative water production prior to the gas injection-to-oil development phase. g2 B is the gas volume coefficient at reservoir pressure P2. o2 B is the crude oil volume factor at reservoir pressure P2. o3 B is the crude oil volume factor at reservoir pressure P3. w2 C is the water volume factor when the reservoir pressure is P2. g C is the gas compressibility coefficient. f C is the rock compressibility coefficient. o C is the compressibility coefficient of crude oil. w The water compressibility coefficient.

9. The calculation method according to any one of claims 6-8, characterized in that, The expression for the dynamic reserves N of the reservoir is:

10. The calculation method according to any one of claims 6-9, characterized in that, The expression for the reservoir water volume W is:

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