Quantitative splitting method for contribution rate of carbon dioxide burying mechanism

Abstract

The invention discloses a carbon dioxide burying mechanism contribution rate quantitative splitting method, belongs to the technical field of oil and gas field development, and solves the problem that the contribution rates of different sealing mechanisms to the CO2 sealing amount cannot be quantitatively split in the prior art. A carbon dioxide oil displacement experiment is conducted, carbon dioxide gas is injected into the displacement rock core, and the water dissolution and storage contribution rate, the oil dissolution and storage contribution rate and the retention and storage contribution rate in the carbon dioxide oil displacement process are calculated; according to the method, a carbon dioxide water displacement experiment and a carbon dioxide oil displacement experiment are combined, on the basis of the mass conservation theory, the calculation method for the contribution rate of different quantitative splitting sealing mechanisms to the carbon dioxide sealing amount is established, the carbon dioxide burying potential under different geological conditions can be accurately evaluated, and therefore the optimal burying site is selected.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to a method for quantitatively splitting the contribution rate of a carbon dioxide storage mechanism. Background Art

[0002] CO2 geological storage is an important part of CCUS technology. On the premise of having complete geological data, well network system and transportation pipelines, CO2 enhanced oil and gas recovery and geological storage integrated technology (CO2-EOR) has considerable economic benefits. It has entered the commercial application stage abroad and the industrial demonstration stage in China. According to the main control factors of storage, the CO2 storage mechanism in CO2-EOR technology can be divided into free gas retention storage, water dissolution storage and oil dissolution storage. However, there is still a lack of research on the contribution rate of the above storage mechanisms to CO2 storage. Clarifying the contribution of different storage mechanisms to CO2 storage is conducive to the targeted development of CO2 storage technology and methods.

[0003] The Chinese invention patent with application number "202210302896.3" discloses "a method and device for evaluating CO2 storage in fractured oil reservoir geological bodies". The invention is based on the cores obtained from the target oil reservoir geological body. Through the formation water core displacement experiment, the carbon dioxide storage rate in the fractured cores with different conductivity is calculated, and the quantitative relationship between the carbon dioxide storage rate and the fracture parameters is obtained, which provides guidance for the optimization of the displacement method of fractured oil reservoirs. However, although the above patent has established a systematic evaluation method and device for evaluating CO2 oil recovery and storage efficiency, it does not consider the contribution of different storage mechanisms to CO2 storage, and only provides an overall storage potential evaluation method.

[0004] The Chinese invention patent with application number "202211620485.5" discloses "an injection and production method and system based on the carbon dioxide storage capacity in the oil recovery process". This method is based on the actual data of the oil field mine, and establishes a numerical model of five-point well network injection and production coupling and a numerical model of five-point well network continuous injection and production. According to the numerical model corresponding to the target injection and production method, the injection and production process parameters are obtained by simulation experiments under the target injection and production half-cycle ratio and the target injection and production cycle, and the carbon dioxide injection rate when the carbon dioxide storage capacity is the largest is determined. However, the above method also ignores the contribution rate and influence of different CO2 storage mechanisms on the maximum CO2 storage capacity. At the same time, the patent is mainly based on numerical simulation and has poor objectivity. In response to the above problems, we proposed a method for quantitative splitting of the contribution rate of carbon dioxide storage mechanism. Summary of the invention

[0005] The purpose of the present invention is to address the shortcomings of the prior art and provide a method for quantitatively splitting the contribution rate of carbon dioxide storage mechanisms, thereby solving the problem that the prior art cannot quantitatively split the contribution rates of different storage mechanisms to the CO2 storage amount.

[0006] The existing technology cannot quantitatively split the contribution rate of different storage mechanisms to the CO2 storage volume. In order to solve the above problems, we proposed a method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism. In short, when implementing the method, we first determine the carbon dioxide state parameters through carbon dioxide PVT test, and then select at least one group of displacement cores with the same physical properties as the target reservoir, wash the oil and dry the multiple groups of displacement cores, load the saturated water displacement cores into the core holder, and assemble the core holder in a single core displacement system. Then, open at least one group of valves of the single core displacement system to conduct carbon dioxide water displacement experiment, and at the same time, open at least one group of valves of the single core displacement system to conduct carbon dioxide oil displacement experiment, open at least one group of valves of the single core displacement system, inject carbon dioxide gas into the displacement core at a constant rate through the first ISCO pump, and use the oil-gas-water separation metering device to record the oil displacement water production V' wo , oil displacement production V' oo and oil displacement gas production V' co , calculate the CO2 oil displacement retention storage volume V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So , the final oil recovery storage capacity based on carbon dioxide is V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So Calculation of water dissolution storage contribution rate ξ during CO2 flooding w 、Oil dissolution storage contribution rateξ o and the retention storage contribution rateξ f , then change the injection rate, back pressure, temperature parameters in the carbon dioxide injection parameters, and the permeability and heterogeneity parameters in the core parameters, and repeat S20-SS70 to study the variation law of the contribution rate of the carbon dioxide storage mechanism under the influence of different parameters. In the embodiment of the present invention, a quantitative splitting method of the contribution rate of the carbon dioxide storage mechanism with simple principle and quantitative analysis is provided. Through the combination of carbon dioxide flooding water experiment and carbon dioxide flooding oil experiment, based on the theory of conservation of mass, a calculation method for quantitatively splitting the contribution rate of different storage mechanisms to the carbon dioxide storage amount is established, which can accurately evaluate the storage potential of carbon dioxide under different geological conditions, so as to select the optimal storage location, and can provide targeted theoretical guidance for carbon dioxide storage design, and also overcome the problem that the existing method cannot quantitatively split the contribution rate of different storage mechanisms to the CO2 storage amount, and the objectivity based on numerical simulation is poor.

[0007] The present invention is implemented as follows: a method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism, comprising:

[0008] S10, determining carbon dioxide state parameters through carbon dioxide PVT testing, and outputting a carbon dioxide state parameter set;

[0009] S20, selecting at least one group of displacement cores with the same physical properties as the target reservoir, washing the oil and drying the multiple groups of displacement cores, using a vacuum pump to evacuate the displacement cores for 4 hours, and allowing the displacement cores to self-absorb saturated simulated water for more than 2 hours, and recording the displacement core volume V p ;

[0010] S30, loading the water-saturated displacement core into a core holder, assembling the core holder in a single core displacement system, checking the air tightness of the single core displacement system under a high pressure condition of not less than 18 MPa, connecting a carbon dioxide gas cylinder to a gas booster of the single core displacement system, and pumping carbon dioxide into a carbon dioxide piston container of the single core displacement system to a required pressure;

[0011] S40, open at least one set of valves of a single core displacement system to conduct a carbon dioxide water displacement experiment, use a first ISCO pump to inject carbon dioxide gas into the displacement core, and record the water production V of the water displacement through the oil, gas and water separation metering device. wo and water displacement gas production V co , the volume of carbon dioxide pumped in by the first ISCO pump measures the amount of carbon dioxide injected into the water drive V ci , calculate the water flooding storage rate η of carbon dioxide, where water flooding retention storage means that carbon dioxide is retained in the pores of the water displaced by it in the form of free gas, and calculate the water flooding retention storage capacity V Sf and the amount of water dissolved and stored V Sw ;

[0012] The water storage rate η of carbon dioxide is calculated by the following formula:

[0013]

[0014] V S =V ci -V co (2)

[0015] Among them, V s is the total amount of carbon dioxide flooding and storage, η is the carbon dioxide flooding and storage rate;

[0016] S50, open at least one set of valves in the single core displacement system to conduct a carbon dioxide flooding experiment, and record the final volume of produced water as the volume of crude oil saturated into the core V o ;

[0017] S60, open at least one set of valves of the single core displacement system, inject carbon dioxide gas into the displacement core at a constant rate through the first ISCO pump, and use the oil, gas and water separation metering device to record the oil displacement water production V' wo , oil displacement production V' oo and oil displacement gas production V' co , the volume of carbon dioxide pumped in by the first ISCO pump measures the amount of carbon dioxide injected into the oil recovery V' ci , calculate the CO2 oil displacement retention storage volume V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So ;

[0018] S70, obtaining the oil displacement retention storage volume V' of carbon dioxide Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So , based on the CO2 oil displacement retention storage capacity V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So Calculation of water dissolution storage contribution rate ξ during CO2 flooding w 、Oil dissolution storage contribution rateξ o and the retention storage contribution rateξ f ;

[0019] Among them, the contribution rate of water dissolution storage is ξ w 、Oil dissolution storage contribution rateξ o and the retention storage contribution rateξ f Calculated by the following formula:

[0020] ξ w =V' Sw / V' S (8)

[0021] ξ o =V' So / V' S (9)

[0022] ξ f =V' Sf / V' S (10)

[0023] S80, changing the injection rate, back pressure, and temperature parameters in the carbon dioxide injection parameters, and the permeability and heterogeneity parameters in the core parameters, and repeating S20-SS70.

[0024] The single core displacement system comprises:

[0025] Carbon dioxide cylinders, used to provide carbon dioxide gas;

[0026] A pump gas group is used to pump carbon dioxide gas into a single core displacement system, and the pump gas group is connected to the carbon dioxide gas cylinder;

[0027] A gas booster, connected to the carbon dioxide cylinder, for boosting the pressure of the carbon dioxide;

[0028] A simulation container group, the simulation container group is connected to the pump gas group, and the simulation container group is used to simulate the flow behavior of carbon dioxide, water, and oil fluids under formation conditions;

[0029] A six-way valve connected to the simulation container group;

[0030] The core holder is used to hold and protect the displacement core, and the core holder is connected to the six-way valve;

[0031] A back pressure valve is arranged on one side of the core holder, and the back pressure valve is connected to the core holder;

[0032] The oil, gas and water separation metering device is used to record the water production, oil production and gas production of oil displacement, and the oil, gas and water separation metering device is connected with the back pressure valve;

[0033] A valve group is used to open and close the single core displacement system.

[0034] The pump gas group comprises:

[0035] A first ISCO pump, the first ISCO pump is arranged on one side of the simulation container group, and the first ISCO pump is connected to the simulation container group;

[0036] The second ISCO pump is arranged at one side of the core holder, and the second ISCO pump is connected to the back pressure valve.

[0037] The simulation container group includes:

[0038] CO2 piston container;

[0039] Simulated water piston container;

[0040] The simulated oil piston container, the carbon dioxide piston container, the simulated water piston container, and the simulated oil piston container are respectively connected to the first ISCO pump, the gas booster, and the six-way valve.

[0041] The valve group includes valve A, valve B, valve C, valve D, valve E, valve F, valve G, valve H, valve I, valve J, and valve K. The valve A is arranged between the carbon dioxide cylinder and the gas booster, the valve B is installed at the exhaust port of the first ISCO pump, the valve C and valve F are respectively installed at both ends of the carbon dioxide piston container, the valve D and valve G are respectively installed at both ends of the simulated water piston container, the valve E and valve H are respectively installed at both ends of the simulated oil piston container, the valve H is arranged between the six-way valve and the core clamp, the valve I is arranged between the core clamp and the back pressure valve, the valve J is arranged between the oil, gas and water separation metering device and the back pressure valve, and the valve K is arranged between the second ISCO pump and the back pressure valve.

[0042] In step S40, when at least one set of valves of a single core displacement system is opened to perform a carbon dioxide flooding experiment, valve B, valve C, valve F, valve I, valve J and valve K are opened, and carbon dioxide gas is injected into the displacement core at a constant rate using a first ISCO pump;

[0043] Flooding water retention storage volume V Sf and the amount of water dissolved and stored V Sw Calculated by the following formula:

[0044] V Sf =V wo -V wi (3)

[0045] V S =V Sf +V Sw =(V ci -V co )-(V wo -V wi ) (4)

[0046] Among them, V Sf is the water retention storage capacity, V Sw Indicates the amount of water dissolved and stored in the flooding water, V s The total amount of carbon dioxide flooding and water storage.

[0047] In step S50, when at least one set of valves of a single core displacement system is opened to conduct a carbon dioxide oil recovery experiment, valve B, valve E, valve H, valve I, valve J and valve K are opened, and simulated oil is injected according to the cross-sectional area of ​​the displacement core until no water is produced, and then the injection speed of simulated oil is gradually increased 3-5 times.

[0048] In step S60, when carbon dioxide gas is injected into the displacement core at a constant rate through the first ISCO pump, valve B, valve D, valve E, valve G, valve H, valve I, valve J and valve K are opened;

[0049] CO2 oil displacement retention storage capacity V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So Calculated by the following formula:

[0050] V' Sf =V wo +V oo -V wi (5)

[0051]

[0052] V' S =V' Sf +V' Sw +V' So (7)

[0053] Among them, the amount of oil dissolved and stored is V' So is the total oil storage capacity V' S and oil displacement retention storage volume V' Sf and the amount of dissolved oil-displacement water V' So difference.

[0054] The displacement core is a natural core, an outcrop core or an artificial homogeneous core, the displacement core has a diameter of 3.8 cm, a length of 30 cm, a gas permeability of 800 mD, and a porosity of 25%;

[0055] The carbon dioxide PVT test was carried out using a conventional PVT test device, the reservoir temperature was 55°C, and the experimental pressures were 5MPa, 16MPa and 34MPa respectively.

[0056] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0057] The present invention provides a quantitative splitting method for the contribution rate of carbon dioxide storage mechanism which has a simple principle and can be quantitatively analyzed. By combining carbon dioxide water displacement experiments and carbon dioxide oil displacement experiments, a calculation method for quantitatively splitting the contribution rate of different storage mechanisms to the carbon dioxide storage amount is established based on the mass conservation theory. The carbon dioxide storage potential under different geological conditions can be accurately evaluated, so as to select the optimal storage site, and targeted theoretical guidance can be provided for carbon dioxide storage design. The problem that the existing methods cannot quantitatively split the contribution rate of different storage mechanisms to the CO2 storage amount and the objectivity based on numerical simulation is poor is overcome. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of the implementation flow of a method for quantitatively splitting the contribution rate of the carbon dioxide storage mechanism provided by the present invention.

[0059] Figure 2 It is a structural schematic diagram of a single core displacement system provided by the present invention.

[0060] Figure 3 The carbon dioxide storage rate curves of Examples 1 to 6 of the present invention are shown.

[0061] Figure 4 The storage contribution rate curves of various storage mechanisms in the carbon dioxide flooding experiment are shown.

[0062] In the figure: 1-carbon dioxide cylinder, 2-first ISCO pump, 3-valve group, 4-gas booster, 5-carbon dioxide piston container, 6-simulated water piston container, 7-simulated oil piston container, 8-six-way valve, 9-core clamp, 10-oil, gas and water separation metering device, 11-back pressure valve, 12-second ISCO pump. DETAILED DESCRIPTION

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0064] The existing technology cannot quantitatively split the contribution rate of different storage mechanisms to the CO2 storage volume. In order to solve the above problems, we propose a method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism. In short, when implementing the method, the carbon dioxide state parameters are first determined through carbon dioxide PVT testing, and then at least one group of displacement cores with the same physical properties as the target reservoir are selected, and multiple groups of displacement cores are subjected to oil washing and drying treatments. The saturated displacement cores are loaded into the core holder 9, and the core holder 9 is assembled in a single core displacement system. Then, at least one group of valves of the single core displacement system is opened to conduct a carbon dioxide water flooding experiment, and at the same time, at least one group of valves of the single core displacement system is opened to conduct a carbon dioxide oil flooding experiment. At least one group of valves of the single core displacement system is opened, and carbon dioxide gas is injected into the displacement core at a constant rate through the first ISCO pump 2, and the oil-gas-water separation metering device 10 is used to record the oil displacement water production V' wo , oil displacement production V' oo and oil displacement gas production V' co , calculate the CO2 oil displacement retention storage volume V' Sf, Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So , the final oil recovery storage capacity based on carbon dioxide is V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So Calculation of water dissolution storage contribution rate ξ during CO2 flooding w 、Oil dissolution storage contribution rateξ o and the retention storage contribution rateξ f , then change the injection rate, back pressure, temperature parameters in the carbon dioxide injection parameters, and the permeability and heterogeneity parameters in the core parameters, and repeat S20-SS70 to study the variation law of the contribution rate of the carbon dioxide storage mechanism under the influence of different parameters. In the embodiment of the present invention, a quantitative splitting method of the contribution rate of the carbon dioxide storage mechanism with simple principle and quantitative analysis is provided. Through the combination of carbon dioxide flooding water experiment and carbon dioxide flooding oil experiment, based on the theory of conservation of mass, a calculation method for quantitatively splitting the contribution rate of different storage mechanisms to the carbon dioxide storage amount is established, which can accurately evaluate the storage potential of carbon dioxide under different geological conditions, so as to select the optimal storage location, and can provide targeted theoretical guidance for carbon dioxide storage design, and also overcome the problem that the existing method cannot quantitatively split the contribution rate of different storage mechanisms to the CO2 storage amount, and the objectivity based on numerical simulation is poor.

[0065] The embodiment of the present invention provides a method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism. Figure 1 The schematic diagram of the implementation process of the quantitative splitting method of the carbon dioxide storage mechanism contribution rate is shown. The quantitative splitting method of the carbon dioxide storage mechanism contribution rate specifically includes:

[0066] S10, determining carbon dioxide state parameters through carbon dioxide PVT testing, and outputting a carbon dioxide state parameter set;

[0067] In this embodiment, a conventional PVT test device is used to perform a PVT test on carbon dioxide during a carbon dioxide PVT test, and the operating volume (i.e., reservoir temperature and pressure conditions) under reservoir temperature and pressure conditions (depending on the actual reservoir) is calculated. Unless otherwise specified, all carbon dioxide mentioned in this embodiment refers to the converted operating volume. In addition, the volume of carbon dioxide under different temperature and pressure conditions can also be calculated in combination with empirical formulas and theoretical formulas such as the standard gas state equation (gaseous state) and Peng's equation (supercritical state), which are also applicable to this embodiment. However, its accuracy is poorer than that of the PVT test. During the test, the reservoir temperature was 55°C, and the experimental pressures were 5MPa, 16MPa, and 34MPa, respectively. The specific volumes of carbon dioxide obtained from the test were 0.010m 3 / Kg,0.0018m 3 / Kg and 0.001m 3 / Kg. Under working conditions, its density is close to that of water, and the volume of carbon dioxide during the experiment can be calculated based on the law of conservation of mass.

[0068] S20, selecting at least one group of displacement cores with the same physical properties as the target reservoir, washing the oil and drying the multiple groups of displacement cores, using a vacuum pump to evacuate the displacement cores for 4 hours, and allowing the displacement cores to self-absorb saturated simulated water for more than 2 hours, and recording the displacement core volume V p In this embodiment, the displacement core is a natural core, an outcrop core or an artificial homogeneous core, the diameter of the displacement core is 3.8 cm, the length is 30 cm, the gas permeability is 800 mD, and the porosity is 25%; at the same time, in order to ensure the experimental accuracy, the pore volume of the length displacement core is generally not less than 50 mL.

[0069] S30, the water-saturated displacement core is loaded into the core holder 9, the core holder 9 is assembled in the single core displacement system, the air tightness of the single core displacement system is checked under a high pressure condition of not less than 18 MPa, the carbon dioxide cylinder 1 is connected to the gas booster 4 of the single core displacement system, and carbon dioxide is pumped into the carbon dioxide piston container 5 of the single core displacement system to the required pressure;

[0070] In this embodiment, the core holder 9 saturated with water is connected to the experimental process according to the arrangement relationship of the single core displacement system, and the air tightness of the system is checked under a high pressure of 35 MPa. The carbon dioxide cylinder 1 is connected to the gas booster 4, and carbon dioxide is filled into the carbon dioxide piston container 5 to the pressure required for the experiment. During the carbon dioxide pressurization process, all valve groups 3 are first closed, and valves A and F are opened. After the pressure in valve F reaches the preset pressure, valves A and F are closed. Valve K is opened, and a certain value of back pressure is applied to the back pressure valve 11 using the second ISCO pump 12.

[0071] S40, open at least one set of valves of a single core displacement system to conduct a carbon dioxide water displacement experiment, use a first ISCO pump 2 to inject carbon dioxide gas into the displacement core, and record the water production V of the water displacement through the oil, gas and water separation metering device 10. wo and water displacement gas production V co The volume of carbon dioxide pumped in by the first ISCO pump 2 measures the amount of carbon dioxide injected into the water V ci , calculate the water flooding storage rate η of carbon dioxide, where water flooding retention storage means that carbon dioxide is retained in the pores of the water displaced by it in the form of free gas, and calculate the water flooding retention storage capacity V Sf and the amount of water dissolved and stored V Sw ;

[0072] The water storage rate η of carbon dioxide is calculated by the following formula:

[0073]

[0074] V S =V ci -V co (2)

[0075] Among them, V s is the total amount of carbon dioxide stored in water flooding, η is the carbon dioxide storage rate in water flooding; the storage of carbon dioxide mainly comes from retention storage and water dissolution storage, among which retention storage is mainly the retention of carbon dioxide in the pores of the water displaced by it in the form of free gas, and the retention storage amount V Sf Calculated by formula (3); the corresponding water-soluble storage volume V Sw The total storage volume V S The difference between the retained storage volume and the retained storage volume is calculated using formula (4).

[0076] In step S40 of this embodiment, when at least one set of valves of a single core displacement system is opened to perform a carbon dioxide flooding experiment, valve B, valve C, valve F, valve I, valve J, and valve K are opened, and the first ISCO pump 2 is used to inject carbon dioxide gas into the displacement core at a constant rate;

[0077] Flooding water retention storage volume V Sf and the amount of water dissolved and stored V Sw Calculated by the following formula:

[0078] V Sf =V wo -V wi (3)

[0079] V S =V Sf +V Sw =(V ci -V co )-(V wo -V wi ) (4)

[0080] Among them, V Sf is the water retention storage capacity, V Sw Indicates the amount of water dissolved and stored in the flooding water, V s The total amount of carbon dioxide flooding and water storage.

[0081] In particular, the present invention is also applicable to the splitting of the carbon dioxide storage mechanism in the carbon dioxide foam flooding process. In this case, the foaming agent and carbon dioxide need to be injected into the core holder 9 at the same time, and the other processes remain unchanged. If it is a carbon dioxide displacement process, the liquid injection amount V in formula (3) is wi0. In order to better measure the gas-liquid volume, a certain mass fraction of defoaming agent needs to be dissolved in the water of the drainage gas recovery device.

[0082] S50, open at least one set of valves in the single core displacement system to conduct a carbon dioxide flooding experiment, and record the final volume of produced water as the volume of crude oil saturated into the core V o ;

[0083] In step S50, when at least one set of valves of a single core displacement system is opened to carry out a carbon dioxide flooding experiment, a displacement core with parallel comparison is selected to repeat S20 and S30, valve B, valve E, valve H, valve I, valve J and valve K are opened, and simulated oil is injected at a rate of 0.1 mL / min until no water is produced, and then the injection rate of simulated oil is gradually increased to 0.2 mL / min, 0.3 mL / min and 0.5 mL / min, respectively, and simulated oil is injected according to the cross-sectional area of ​​the displacement core until no water is produced, and then the injection rate of simulated oil is gradually increased 3-5 times.

[0084] S60, open at least one set of valves of the single core displacement system, inject carbon dioxide gas into the displacement core at a constant rate through the first ISCO pump 2, and use the oil, gas and water separation metering device 10 to record the oil displacement water production V' wo , oil displacement production V' oo and oil displacement gas production V' co , the volume of carbon dioxide pumped in by the first ISCO pump 2 measures the amount of carbon dioxide injected into the oil recovery V' ci , calculate the CO2 oil displacement retention storage volume V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So ;

[0085] In step S60, when carbon dioxide gas is injected into the displacement core at a constant rate through the first ISCO pump 2, valve B, valve D, valve E, valve G, valve H, valve I, valve J and valve K are opened;

[0086] CO2 oil displacement retention storage capacity V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So Calculated by the following formula:

[0087] V' Sf =V wo +V oo -V wi (5)

[0088] Assuming that the amount of dissolved carbon dioxide per unit water volume remains constant during carbon dioxide flooding and oil flooding, the amount of dissolved water stored in the oil flooding process V' Sw It can be calculated by formula (6):

[0089]

[0090] V' S =V' Sf +V' Sw +V' So (7)

[0091] Where: V p +V wi -V wo =V p -(V wo -V wi ), which is the amount of water remaining in the core after CO2 flooding; V p -V o V' is the amount of water remaining in the core after CO2 flooding saturates the oil. wi -V' wo =-(V' wi -V' wo ), and similarly, the amount of water retained in the core after carbon dioxide flooding, where V' is the amount of oil dissolved and stored in the flooding oil. So is the total oil storage capacity V' S and oil displacement retention storage volume V' Sf and the amount of dissolved oil-displacement water V' So difference.

[0092] S70, obtaining the oil displacement retention storage volume V' of carbon dioxide Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So , based on the CO2 oil displacement retention storage capacity V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So Calculation of water dissolution storage contribution rate ξ during CO2 flooding w 、Oil dissolution storage contribution rateξ o and the retention storage contribution rateξ f ;

[0093] Among them, the contribution rate of water dissolution storage is ξ w 、Oil dissolution storage contribution rateξ o and the retention storage contribution rateξ f Calculated by the following formula:

[0094] ξ w =V'Sw / V' S (8)

[0095] ξ o =V' So / V' S (9)

[0096] ξ f =V' Sf / V' S (10)

[0097] S80, change the injection rate, back pressure, temperature parameters in the carbon dioxide injection parameters, permeability, heterogeneity parameters in the core parameters, repeat S20-SS70 to study the change law of the contribution rate of carbon dioxide storage mechanism under the influence of different parameters.

[0098] In the embodiment of the present invention, a quantitative splitting method for the contribution rate of carbon dioxide storage mechanism which is simple in principle and can be quantitatively analyzed is provided. By combining carbon dioxide water displacement experiments and carbon dioxide oil displacement experiments, a calculation method for quantitatively splitting the contribution rate of different storage mechanisms to the carbon dioxide storage amount is established based on the mass conservation theory. The storage potential of carbon dioxide under different geological conditions can be accurately evaluated, so as to select the optimal storage site, and targeted theoretical guidance can be provided for carbon dioxide storage design. The problem that the existing methods cannot quantitatively split the contribution rate of different storage mechanisms to the CO2 storage amount and the objectivity based on numerical simulation is poor is overcome.

[0099] In this embodiment, if Figure 2 As shown, the single core displacement system comprises:

[0100] A carbon dioxide gas cylinder 1, used for providing carbon dioxide gas;

[0101] A pump gas group is used to pump carbon dioxide gas into a single core displacement system, and the pump gas group is connected to the carbon dioxide gas cylinder 1;

[0102] The gas booster 4 is connected to the carbon dioxide cylinder 1 and is used to pressurize the carbon dioxide. The gas booster 4 is a pneumatic booster, a plunger type, or a diaphragm type booster;

[0103] A simulation container group, the simulation container group is connected to the pump gas group, and the simulation container group is used to simulate the flow behavior of carbon dioxide, water, and oil fluids under formation conditions;

[0104] A six-way valve 8 is connected to the simulation container group;

[0105] The core holder 9 is used to hold and protect the displacement core, and the core holder 9 is connected to the six-way valve 8;

[0106] A back pressure valve 11 is arranged on one side of the core holder 9, and the back pressure valve 11 is connected to the core holder 9;

[0107] The oil, gas and water separation metering device 10 is used to record the oil displacement water production, oil displacement oil production and oil displacement gas production, and the oil, gas and water separation metering device 10 is connected to the back pressure valve 11;

[0108] In this embodiment, the oil, gas and water separation metering device 10 is an oil, gas and water three-phase metering device. The oil, gas and water separation metering device 10 is used in conjunction with the water drainage gas production method to record the volume of carbon dioxide produced, the volume of water produced and the volume of oil produced, and the volume of carbon dioxide retained and sealed and the volume of carbon dioxide dissolved and sealed are obtained based on the principle of conservation of mass.

[0109] A valve group 3 is used to open and close the single core displacement system.

[0110] In this embodiment, the pump gas group includes:

[0111] A first ISCO pump 2, the first ISCO pump 2 is arranged on one side of the simulation container group, and the first ISCO pump 2 is connected to the simulation container group;

[0112] The second ISCO pump 12 is disposed at one side of the core holder 9 , and the second ISCO pump 12 is connected to the back pressure valve 11 .

[0113] In this embodiment, the first ISCO pump 2 and the second ISCO pump 12 have the same specifications, and the first ISCO pump 2 and the second ISCO pump 12 have the functions of accurately controlling flow rate and pressure, pulse-free flow, corrosion resistance, multiple operation modes and easy operation. The model is 30D, 65D, 65DM, 100DX, 260D, 500D or 1000D.

[0114] The simulation container group includes:

[0115] Carbon dioxide piston container 5;

[0116] Simulated water piston container 6;

[0117] The simulated oil piston container 7, the carbon dioxide piston container 5, the simulated water piston container 6, and the simulated oil piston container 7 are respectively connected to the first ISCO pump 2, the gas booster 4 and the six-way valve 8.

[0118] The valve group 3 includes valve A, valve B, valve C, valve D, valve E, valve F, valve G, valve H, valve I, valve J, and valve K. The valve A is arranged between the carbon dioxide cylinder 1 and the gas booster 4, the valve B is installed at the exhaust port of the first ISCO pump 2, the valve C and valve F are respectively installed at both ends of the carbon dioxide piston container 5, the valve D and valve G are respectively installed at both ends of the simulated water piston container 6, the valve E and valve H are respectively installed at both ends of the simulated oil piston container 7, the valve H is arranged between the six-way valve 8 and the core holder 9, the valve I is arranged between the core holder 9 and the back pressure valve 11, the valve J is arranged between the oil-gas-water separation metering device 10 and the back pressure valve 11, and the valve K is arranged between the second ISCO pump 12 and the back pressure valve 11. It should be noted that the valves A, valve B, valve C, valve D, valve E, valve F, valve G, valve H, valve I, valve J, and valve K are fixedly installed by means of flange sealing assembly and buckle.

[0119] According to the method of this embodiment, the contribution rate of different storage mechanisms to carbon dioxide storage can be quantitatively calculated by conducting carbon dioxide water displacement experiments and oil displacement experiments. A total of 3 groups of carbon dioxide water displacement experiments and 3 groups of carbon dioxide oil displacement experiments were carried out, and the specific implementation steps are as follows:

[0120] Example 1

[0121] This example is a carbon dioxide flooding experiment. In S40, the carbon dioxide injection rate is 0.1 mL / min, the core pore volume displaced is 85.02 mL, the back pressure is 16 MPa, and the other steps are the same as S10-S80.

[0122] Example 2

[0123] This example is a carbon dioxide flooding experiment. In S40, the carbon dioxide injection rate is 0.2 mL / min, the core pore volume displaced is 86.24 mL, the back pressure is 16 MPa, and the other steps are the same as S10-S80.

[0124] Example 3

[0125] This example is a carbon dioxide flooding experiment. In S40, the carbon dioxide injection rate is 0.3 mL / min, the core pore volume displaced is 85.39 mL, the back pressure is 16 MPa, and the other steps are the same as S10-S80.

[0126] Example 4

[0127] This example is a carbon dioxide flooding experiment. In S50, the carbon dioxide injection rate is 0.2 mL / min, the core pore volume displaced is 85.67 mL, the back pressure is 5 MPa, and the other steps are the same as S10-S80.

[0128] Example 5

[0129] This example is a carbon dioxide flooding experiment. In S50, the carbon dioxide injection rate is 0.2 mL / min, the core pore volume displaced is 85.97 mL, the back pressure is 16 MPa, and the other steps are the same as S10-S80.

[0130] Example 6

[0131] This example is a carbon dioxide flooding experiment. In S50, the carbon dioxide injection rate is 0.2 mL / min, the core pore volume displaced is 86.31 mL, the back pressure is 34 MPa, and the other steps are the same as S10-S80.

[0132] Table 1 shows the test results of the sealing rate and sealing contribution rate of Examples 1 to 6 of the present invention.

[0133] Table 1

[0134]

[0135]

[0136] and Figure 3 The carbon dioxide storage rate curves of Examples 1 to 6 of the present invention are shown. Figure 3 The results show that the overall storage rate of CO2 flooding water is lower than that of CO2 flooding oil. This is mainly because CO2 can be miscible with crude oil, especially under high pressure conditions. As the injection rate increases, the storage rate of CO2 gradually increases. This is because the increase in injection pressure causes more water to be displaced and produced. The higher the pressure of the CO2 flooding experiment and the closer it is to the miscible pressure, the higher the CO2 storage rate. This is mainly because the oil recovery efficiency is improved and the pore space that CO2 can occupy is increased.

[0137] Figure 4 The storage contribution rate curves of various storage mechanisms in the CO2 flooding experiment are shown. Figure 4 It shows that the contribution rate of carbon dioxide retention storage is obviously the largest, at more than 68%, and gradually increases with the increase of experimental pressure, which is mainly due to the improved oil recovery effect. At the same time, the water dissolution storage rate remains basically unchanged, because there is no external water supply during the carbon dioxide recovery experiment, and the residual water content in the core remains basically unchanged. Figure 4 Note that the contribution rate of carbon dioxide storage is: retention storage > oil dissolution storage > water dissolution storage.

[0138] In summary, the present invention provides a method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism. In an embodiment of the present invention, a method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism is provided, which has a simple principle and can be quantitatively analyzed. By combining carbon dioxide water displacement experiments and carbon dioxide oil displacement experiments, based on the theory of conservation of mass, a calculation method for quantitatively splitting the contribution rate of different storage mechanisms to the carbon dioxide storage amount is established. The storage potential of carbon dioxide under different geological conditions can be accurately evaluated, so as to select the optimal storage site, and targeted theoretical guidance can be provided for carbon dioxide storage design. The problem that the existing methods cannot quantitatively split the contribution rate of different storage mechanisms to the CO2 storage amount and the objectivity based on numerical simulation is poor is overcome.

[0139] It should be noted that, for the above-mentioned embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the described order of actions, because according to the present invention, some steps may be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0140] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on these embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field can still combine, add, delete or make other adjustments to the features in the various embodiments of the present invention according to the circumstances without conflict, without making creative work, so as to obtain different other technical solutions that do not deviate from the concept of the present invention in essence, and these technical solutions also belong to the scope of protection of the present invention.

Claims

1. A method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism, characterized in that: include: S10, determining carbon dioxide state parameters through carbon dioxide PVT testing, and outputting a carbon dioxide state parameter set; S20, selecting at least one group of displacement cores with the same physical properties as the target reservoir, washing the oil and drying the displacement cores, using a vacuum pump to evacuate the displacement cores for 4 hours, allowing the displacement cores to self-absorb saturated simulated water for more than 2 hours, and recording the displacement core volume V p ; S30, loading the water-saturated displacement core into a core holder, assembling the core holder in a single core displacement system, checking the air tightness of the single core displacement system under a high pressure condition of not less than 18 MPa, connecting a carbon dioxide gas cylinder to a gas booster of the single core displacement system, and pumping carbon dioxide into a carbon dioxide piston container of the single core displacement system to a required pressure; S40, open at least one set of valves of a single core displacement system to conduct a carbon dioxide water displacement experiment, use a first ISCO pump to inject carbon dioxide gas into the displacement core, and record the water production V of the water displacement through the oil, gas and water separation metering device. wo and water displacement gas production V co , the volume of carbon dioxide pumped in by the first ISCO pump measures the amount of carbon dioxide injected into the water drive V ci , calculate the water flooding storage rate η of carbon dioxide, where water flooding retention storage means that carbon dioxide is retained in the pores of the water displaced by it in the form of free gas, and calculate the water flooding retention storage capacity V Sf and the amount of water dissolved and stored V Sw ; The water storage rate η of carbon dioxide is calculated by the following formula: V S =V ci -V co (2) Among them, V s is the total amount of carbon dioxide flooding and storage, η is the carbon dioxide flooding and storage rate; S50, open at least one set of valves in the single core displacement system to conduct a carbon dioxide flooding experiment, and record the final volume of produced water as the volume of crude oil saturated into the core V o ; S60, open at least one set of valves of the single core displacement system, inject carbon dioxide gas into the displacement core at a constant rate through the first ISCO pump, and use the oil, gas and water separation metering device to record the oil displacement water production V' wo , oil displacement production V' oo and oil displacement gas production V' co , the volume of carbon dioxide pumped in by the first ISCO pump measures the amount of carbon dioxide injected into the oil recovery V' ci , calculate the CO2 oil displacement retention storage volume V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So .

2. The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism according to claim 1, characterized in that: The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism also includes: S70, obtaining the oil displacement retention storage volume V' of carbon dioxide Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So , based on the CO2 oil displacement retention storage capacity V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So Calculation of water dissolution storage contribution rate ξ during CO2 flooding w 、Oil dissolution storage contribution rateξ o and the retention storage contribution rateξ f ; Among them, the contribution rate of water dissolution storage is ξ w 、Oil dissolution storage contribution rateξ o and the retention storage contribution rateξ f Calculated by the following formula: ξ w =V' Sw / V' S (8) ξ o =V' So / V' S (9) ξ f =V' Sf / V' S (10) S80, changing the injection rate, back pressure, and temperature parameters in the carbon dioxide injection parameters, and the permeability and heterogeneity parameters in the core parameters, and repeating S20-SS70.

3. The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism according to claim 1, characterized in that: The single core displacement system comprises: Carbon dioxide cylinders, used to provide carbon dioxide gas; A pump gas group is used to pump carbon dioxide gas into a single core displacement system, and the pump gas group is connected to the carbon dioxide gas cylinder; A gas booster, connected to the carbon dioxide cylinder, for boosting the pressure of the carbon dioxide; A simulation container group, the simulation container group is connected to the pump gas group, and the simulation container group is used to simulate the flow behavior of carbon dioxide, water, and oil fluids under formation conditions; A six-way valve connected to the simulation container group; The core holder is used to hold and protect the displacement core, and the core holder is connected to the six-way valve; A back pressure valve is arranged on one side of the core holder, and the back pressure valve is connected to the core holder; The oil, gas and water separation metering device is used to record the water production, oil production and gas production of oil displacement, and the oil, gas and water separation metering device is connected with the back pressure valve; A valve group is used to open and close the single core displacement system.

4. The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism according to claim 3, characterized in that: The pump gas group comprises: A first ISCO pump, the first ISCO pump is arranged on one side of the simulation container group, and the first ISCO pump is connected to the simulation container group; The second ISCO pump is arranged at one side of the core holder, and the second ISCO pump is connected to the back pressure valve.

5. The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism according to claim 4, characterized in that: The simulation container group includes: CO2 piston container; Simulated water piston container; The simulated oil piston container, the carbon dioxide piston container, the simulated water piston container, and the simulated oil piston container are respectively connected to the first ISCO pump, the gas booster, and the six-way valve.

6. The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism according to claim 5, characterized in that: The valve group includes valve A, valve B, valve C, valve D, valve E, valve F, valve G, valve H, valve I, valve J, and valve K. The valve A is arranged between the carbon dioxide cylinder and the gas booster, the valve B is installed at the exhaust port of the first ISCO pump, the valve C and valve F are respectively installed at both ends of the carbon dioxide piston container, the valve D and valve G are respectively installed at both ends of the simulated water piston container, the valve E and valve H are respectively installed at both ends of the simulated oil piston container, the valve H is arranged between the six-way valve and the core clamp, the valve I is arranged between the core clamp and the back pressure valve, the valve J is arranged between the oil, gas and water separation metering device and the back pressure valve, and the valve K is arranged between the second ISCO pump and the back pressure valve.

7. The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism according to claim 1, characterized in that: In step S40, when at least one set of valves of a single core displacement system is opened to perform a carbon dioxide flooding experiment, valve B, valve C, valve F, valve I, valve J and valve K are opened, and carbon dioxide gas is injected into the displacement core at a constant rate using a first ISCO pump; Flooding water retention storage volume V Sf and the amount of water dissolved and stored V Sw Calculated by the following formula: V Sf =V wo -V wi (3) V S =V Sf +V Sw =(V ci -V co )-(V wo -V wi ) (4) Among them, V Sf is the water retention storage capacity, V Sw Indicates the amount of water dissolved and stored in the flooding water, V s The total amount of carbon dioxide flooding and water storage.

8. The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism according to claim 7, characterized in that: In step S50, when at least one set of valves of a single core displacement system is opened to conduct a carbon dioxide oil recovery experiment, valve B, valve E, valve H, valve I, valve J and valve K are opened, and simulated oil is injected according to the cross-sectional area of ​​the displacement core until no water is produced, and then the injection speed of simulated oil is gradually increased 3-5 times.

9. The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism according to claim 1, characterized in that: In step S60, when carbon dioxide gas is injected into the displacement core at a constant rate through the first ISCO pump, valve B, valve D, valve E, valve G, valve H, valve I, valve J and valve K are opened; CO2 oil displacement retention storage capacity V' Sf , Dissolved storage volume of oil displacement water V' Sw , Dissolved oil storage volume V' So Calculated by the following formula: V' Sf =V wo +V oo -V wi (5) V S '=V S ' f +V S ' w +V S ' o (7) Among them, the amount of oil dissolved and stored is V' So is the total oil storage capacity V' S and oil displacement retention storage volume V' Sf and the amount of dissolved oil-displacement water V' So difference.

10. The method for quantitatively splitting the contribution rate of carbon dioxide storage mechanism according to claim 9, characterized in that: The displacement core is a natural core, an outcrop core or an artificial homogeneous core, the displacement core has a diameter of 3.8 cm, a length of 30 cm, a gas permeability of 800 mD, and a porosity of 25%; The carbon dioxide PVT test was carried out using a conventional PVT test device, the reservoir temperature was 55°C, and the experimental pressures were 5MPa, 16MPa and 34MPa respectively.

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