Method for measuring carbon dioxide dynamic constraint burying amount in carbon dioxide oil displacement burying process

Abstract

A method for measuring the carbon dioxide dynamic constraint burying amount in the carbon dioxide oil displacement burying process comprises the steps that based on a rock core displacement experiment, the porosity is calculated, and a to-be-measured rock core saturated with simulated oil is obtained; acquiring a CT value of the to-be-tested rock core saturated by the simulated oil, taking the CT value as an initial state, then performing carbon dioxide displacement, and acquiring CT values at different moments in the displacement process; drawing a relation curve of the carbon dioxide saturation and the relative permeability of the core to be measured; the on-way carbon dioxide relative permeability of the rock core to be measured at different moments is obtained; and calculating the carbon dioxide bound burying amount of the to-be-measured rock core at different moments. The method provided by the invention is combined with an on-line CT scanning technology, a relation curve of the rock core carbon dioxide saturation and the relative permeability can be accurately obtained, and then real-time dynamic observation of the carbon dioxide constraint retention condition in the carbon dioxide flooding embedding process is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon dioxide storage, and relates to a method for measuring the storage amount of carbon dioxide, in particular to a method for measuring the dynamic bound storage amount of carbon dioxide in the process of carbon dioxide flooding oil storage. BACKGROUND

[0002] Carbon dioxide flooding oil storage is a carbon capture and storage technology, that is, carbon dioxide is injected into a reservoir through an injection well to push crude oil to flow to a production well, increase the production of crude oil, and after the displacement process is completed, the carbon dioxide is extracted together with the crude oil, and after separation, the extracted carbon dioxide is re-injected into the reservoir for storage.

[0003] The storage amount of carbon dioxide is one of the focuses in the process of carbon dioxide capture, utilization and storage. Carbon dioxide storage mainly includes geological structure storage, bound storage, dissolution storage and mineralization storage. Among them, the bound storage relies on the capillary force in the rock pore. At present, the evaluation of the storage amount is still in the basic stage, and the evaluation method is basically based on the calculation of the theoretical storage amount of the reservoir by the volume method, mainly including the US-DOE evaluation method, the CSLF evaluation method and the USGS evaluation method. For example, CN115704785A discloses a method and device system for evaluating the carbon dioxide storage capacity based on nuclear magnetic resonance core flooding, which combines core flooding experiment and nuclear magnetic resonance testing means to provide a calculation method for the storage amount and storage capacity of carbon dioxide in different types of pores at the core scale, and evaluates the carbon dioxide storage capacity of the depleted oil and gas reservoir from the micro perspective. However, the process of carbon dioxide flooding oil storage is a dynamic cycle process, and the static evaluation method is not applicable.

[0004] Therefore, the application provides a method for measuring the dynamic bound storage amount of carbon dioxide in the process of carbon dioxide flooding oil storage by using online CT, which has important significance for large-scale carbon storage test and CCUS-EOR carbon storage evaluation. SUMMARY

[0005] The application aims to provide a method for measuring the dynamic bound storage amount of carbon dioxide in the process of carbon dioxide flooding oil storage, which uses online CT to obtain the dynamic bound storage amount of carbon dioxide in the process of carbon dioxide flooding oil storage, solves the problem that the static evaluation method of the prior art is not applicable to the dynamic flooding oil storage process, and realizes real-time dynamic monitoring of the bound storage amount of carbon dioxide.

[0006] To achieve the application purpose, the following technical scheme is adopted:

[0007] The application provides a method for measuring the dynamic bound storage amount of carbon dioxide in the process of carbon dioxide flooding oil storage, which includes the following steps:

[0008] (1) based on core displacement experiment, calculate the porosity of the measured core, and obtain the measured core saturated with simulated oil;

[0009] (2) CT scanning is performed on the measured core saturated with simulated oil to obtain the CT value as the initial state of the measured core, and then carbon dioxide displacement is performed on the measured core, and CT scanning is performed at different time points of the displacement process to obtain the CT value at different time points of the displacement process;

[0010] (3) the carbon dioxide saturation along the path of the measured core at different time points and the carbon dioxide relative permeability at the displacement outlet are calculated respectively, and the relationship curve of the carbon dioxide saturation and the relative permeability of the measured core is drawn;

[0011] (4) according to the relationship curve, the carbon dioxide relative permeability along the path of the measured core at different time points is obtained;

[0012] (5) the carbon dioxide bound storage amount of the measured core at different time points is calculated.

[0013] The method provided by the application combines online CT scanning technology, and based on core displacement experiment, the relationship curve of the carbon dioxide saturation and the relative permeability of the core can be accurately obtained, and then the carbon dioxide relative permeability along the path of the measured core at different time points and the bound storage amount in the displacement process are calculated, and the real-time dynamic observation of the carbon dioxide bound retention in the carbon dioxide oil displacement and storage process is realized.

[0014] Preferably, the process of step (1) based on core displacement experiment, calculating the porosity of the measured core, and obtaining the measured core saturated with simulated oil comprises:

[0015] (a) determining the confining pressure and displacement pressure difference according to the physical parameters of the measured core;

[0016] (b) vacuumizing the measured core, then saturating it with carbon dioxide, and performing CT scanning respectively to calculate the porosity distribution of the measured core;

[0017] (c) vacuumizing the measured core, saturating it with water, and then displacing it with simulated oil, and the simulated oil is displaced to the outlet of the measured core without water or the displacement multiple is more than 20 PV, and the measured core saturated with simulated oil containing bound water is obtained.

[0018] Preferably, the calculation formula of the porosity is as follows:

[0019]

[0020] wherein, the porosity; CT Satured the CT value of the measured core saturated with carbon dioxide; CT Dry the CT value of the dry core; CTPhase CT is the CT value of carbon dioxide; CT Air CT is the CT value of air.

[0021] Preferably, the CT scanning process at different time points of the displacement process in step (2) comprises: CT scanning once every 60-120 s after the start of displacement, and CT scanning once every 40-100 min after the gas breakthrough at the outlet of the core to be tested.

[0022] Preferably, the formula for calculating the relative permeability of carbon dioxide in step (3) is as follows:

[0023]

[0024] K is the absolute permeability of the core to be tested; A is the cross-sectional area of the core; Δp is the pressure difference between the two ends of the core; V is the volume of fluid at the outlet. rg K is the relative permeability of carbon dioxide; f o is the oil content; L is the length of the core; Q t is the total flow rate; μ o is the viscosity of the simulated oil; μ g is the viscosity of carbon dioxide; K is the absolute permeability of the core to be tested; A is the cross-sectional area of the core; Δp is the pressure difference between the two ends of the core; V is the volume of fluid at the outlet.

[0025] Preferably, the formula for calculating the carbon dioxide saturation in step (3) is as follows:

[0026]

[0027] S is the carbon dioxide saturation; Phase1 is the porosity; CT Two CT is the CT value at any time point of the displacement process; CT Satured2 CT is the CT value of the simulated oil saturated core; CT Phase1 CT is the CT value of carbon dioxide; CT Phase2 CT is the CT value of the simulated oil.

[0028] Preferably, the calculation process of the dynamic carbon dioxide trapped storage in step (5) comprises: calculating the amount of mobile carbon dioxide along the path of the core to be tested according to the relative permeability of carbon dioxide along the path, and the carbon dioxide trapped storage is the difference between the total amount of carbon dioxide retained inside the core to be tested and the amount of mobile carbon dioxide along the path.

[0029] Preferably, the formula for calculating the amount of mobile carbon dioxide along the path is as follows:

[0030]

[0031] Q is the amount of mobile carbon dioxide along the path; K i i ​​is the relative permeability of carbon dioxide along the path; A is the core cross-sectional area; Δp is the differential pressure between the two ends of the core; μ i is the viscosity of carbon dioxide under the current temperature and pressure; L is the core length.

[0032] Preferably, the total amount of carbon dioxide trapped inside the core to be measured is the difference between the gas inlet and outlet amounts of the core to be measured during the displacement process.

[0033] Preferably, the determination method uses a non-steady-state displacement carbon dioxide trapping amount testing device, which comprises a core holder connected to a displacement assembly, a differential pressure recording assembly, a CT scanner, a confining pressure pump, a phase separator, a back pressure pump and a temperature control assembly, respectively.

[0034] The displacement assembly comprises an oil pump connected to the core holder, a water pump and an intermediate container connected to each other and to the core holder.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] The method provided by the present application combines online CT scanning technology and is based on core displacement experiments, so that the relationship curve between carbon dioxide saturation and relative permeability of the core can be accurately obtained, and then the amount of carbon dioxide trapped in the core and the amount of trapped carbon dioxide at different times during the displacement process can be calculated, thereby realizing real-time dynamic observation of the trapped carbon dioxide during the carbon dioxide oil displacement and storage process. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a structural schematic diagram of the non-steady-state displacement carbon dioxide trapping amount testing device provided in Example 1;

[0038] Among them, 1, oil pump; 2, water pump; 3, intermediate container; 4, differential pressure sensor; 5, CT scanner; 6, core holder; 7, confining pressure pump; 8, computer; 9, phase separator; 10, back pressure pump; 11, temperature control box; 12-18, control valve;

[0039] Figure 2 is a CT value diagram of CT scanning of the core to be measured provided in Example 1;

[0040] Figure 3 is a porosity distribution diagram of the core to be measured provided in Example 1;

[0041] Figure 4 is a carbon dioxide saturation along the path diagram of the core to be measured provided in Example 1;

[0042] Figure 5 is a relationship curve between carbon dioxide saturation and relative permeability of the core to be measured provided in Example 1;

[0043] Figure 6 is a relative permeability plot of carbon dioxide along the path of the core to be tested provided in Example 1;

[0044] Figure 7 is the amount of mobile carbon dioxide along the path of the core to be tested provided in Example 1. DETAILED DESCRIPTION

[0045] The technical solutions of the present application are further illustrated by the specific embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0046] Example 1

[0047] The present embodiment provides a method for measuring the dynamic bound storage amount of carbon dioxide in the process of carbon dioxide flooding oil storage, which uses a non-steady-state displacement carbon dioxide retention amount testing device, and the method comprises the following steps:

[0048] (1) Based on the core displacement experiment, the porosity of the core to be tested is calculated, and the core to be tested saturated with simulated oil is obtained.

[0049] Specifically, (1.1) the core to be tested is placed in a core holder, vacuumed and then CT scanned, and then the core is saturated with carbon dioxide and CT scanned again to obtain the average CT value of each scanning plane of the core to be tested. The porosity of the core to be tested is calculated by the obtained CT value, and the porosity distribution along the axial section of the core to be tested is obtained. The calculation formula of the porosity is as follows:

[0050]

[0051] wherein, is the porosity; CT Satured is the CT value of the core to be tested saturated with carbon dioxide; CT Dry is the CT value of the dry core; CT Phase is the CT value of carbon dioxide; CT Air is the CT value of air;

[0052] (1.2) The core to be tested is placed in a core holder, vacuumed and then CT scanned, saturated with water, and then injected into the core to be tested at a constant pressure of 1 MPa using simulated oil for displacement, and gradually increased to 3 MPa and 5 MPa until the displacement multiple is above 20 PV, to obtain the core to be tested saturated with simulated oil containing bound water.

[0053] (2) CT scanning of the core sample saturated with simulated oil to obtain CT value as the initial state of the core sample, and then performing carbon dioxide displacement on the core sample, and CT scanning at different time points of the displacement process to obtain CT value at different time points of the displacement process;

[0054] Specifically, the core sample saturated with simulated oil is recorded at 0 min, CO2 is injected at a constant pressure of 5 MPa, and the amount of carbon dioxide gas, the pressure difference at the inlet and outlet of the core sample is measured at the same time. At the beginning of displacement, CT scanning is performed every 120 seconds, and the pressure difference, the amount of oil and gas at the outlet are recorded every 10 minutes. After gas is observed at the outlet of the core sample, CT scanning is performed every 40 minutes in the later stage of displacement, and CT scanning is performed every 100 minutes in the later stage of displacement to obtain CT value at different time points of the displacement process.

[0055] (3) calculating the carbon dioxide saturation along the core sample and the carbon dioxide relative permeability at the displacement outlet at different time points, respectively, and drawing the relationship curve between the carbon dioxide saturation and the relative permeability of the core sample;

[0056] Specifically, (3.1) according to the gas-liquid data at the displacement outlet of the core sample in the displacement process, the carbon dioxide relative permeability at the displacement outlet of the core sample at each time point is calculated;

[0057] The calculation formula of the carbon dioxide relative permeability is as follows:

[0058]

[0059] Wherein, K rg is the carbon dioxide relative permeability; f o is the oil content; L is the core length; Q t is the total flow rate; μ o is the viscosity of the simulated oil; μ g is the viscosity of carbon dioxide; K is the absolute permeability of the core sample; A is the core cross-sectional area; Δp is the pressure difference between the two ends of the core; V is the fluid volume at the outlet.

[0060] (3.2) calculating the carbon dioxide saturation along the core sample at each time point according to the CT value;

[0061] The calculation formula of the carbon dioxide saturation is as follows:

[0062]

[0063] Wherein, S Phase1 is the carbon dioxide saturation; is the porosity; CT Two is the CT value at any time point of the displacement process; CT Satured2 is the CT value of the core sample saturated with simulated oil; CTPhase1 CT is the CT value of carbon dioxide; CT Phase2 CT is the CT value of the simulation oil;

[0064] (3.3) According to the relative permeability of carbon dioxide at the outlet of the core to be tested and the carbon dioxide saturation along the path, a relationship curve of carbon dioxide saturation and relative permeability is drawn.

[0065] (4) According to the relationship curve, the relative permeability of carbon dioxide along the path of the core to be tested at different times is obtained.

[0066] (5) The amount of carbon dioxide trapped in the core to be tested at different times is calculated;

[0067] Specifically, (5.1) the amount of carbon dioxide along the path in the core to be tested at different times is calculated according to the relative permeability of carbon dioxide along the path, and the calculation formula of the amount of carbon dioxide along the path is as follows:

[0068]

[0069] Wherein, Q i is the amount of carbon dioxide along the path; K i is the relative permeability of carbon dioxide along the path; A is the cross-sectional area of the core; Δp is the pressure difference between the two ends of the core; μ i is the viscosity of carbon dioxide under the current temperature and pressure; L is the length of the core;

[0070] (5.2) The difference between the gas inlet amount and the gas outlet amount of the core to be tested at different times during the displacement process is the total amount of carbon dioxide retained in the core to be tested at different times;

[0071] (5.3) The amount of carbon dioxide trapped at different times is the difference between the total amount of carbon dioxide retained in the core to be tested at different times and the amount of carbon dioxide along the path.

[0072] In this embodiment, the non-steady state displacement carbon dioxide retention amount testing device is as shown in Figure 1 The non-steady state displacement carbon dioxide retention amount testing device comprises a core holder 6 connected with a displacement assembly, a differential pressure recording assembly, a CT scanner 5, a confining pressure pump 7, a phase separator 9, a back pressure pump 10 and a heating and temperature control box 11 respectively;

[0073] The displacement assembly comprises an oil pump 1 connected to the core holder 6, a water pump 2 and an intermediate container 3 connected to each other and to the core holder 6, and the water pump 2 and the intermediate container 3 are used to inject carbon dioxide for displacement;

[0074] The differential pressure recording assembly comprises a differential pressure sensor 4 and a computer 8;

[0075] The connecting pipeline of the connection is provided with a control valve 12-18.

[0076] Example 2

[0077] The embodiment provides a method for measuring dynamic bound storage amount of carbon dioxide in a carbon dioxide oil displacement storage process. The method for measuring provided in the embodiment 1 is used to realize a specific measuring process to illustrate the technical scheme of the application. The method for measuring comprises the following steps:

[0078] (1) According to the method for measuring relative permeability of two-phase fluid in rock (GB / T 28912-2012), the displacement differential pressure of the experiment is 2 MPa. In order to avoid the phenomenon of carbon dioxide miscible displacement, the injection pressure is kept at 5 MPa, and the back pressure is controlled at 3 MPa.

[0079] The core to be measured is placed into a core holder, vacuumized and then CT scanned. The core is saturated with carbon dioxide and then scanned again. Then, the core to be measured is vacuumized and saturated with water, and then CT scanned. Then, the simulated oil is injected into the core to be measured at a constant pressure of 1 MPa to displace, and the pressure is gradually increased to 3 MPa and 5 MPa until the displacement multiple is greater than 20 PV. The core to be measured saturated with the simulated oil and containing bound water is obtained, and CT scanned to obtain the average CT values of the vacuumized core dry scanning, gas saturation, water saturation and oil saturation, wherein the scanning voltage is set to 120 kV, the scanning current is 100 mA, the scanning mode is axial scanning along the core to be measured, and the average CT values of the CT scanning are obtained. The results are shown in the following table. Figure 2

[0080] The porosity distribution of the core to be measured along the axial section is calculated according to the CT values, and the results are shown in the following table. Figure 3

[0081] The core to be measured saturated with the simulated oil is recorded as the 0 min time point of the displacement process.

[0082] (2) Carbon dioxide is injected at a constant pressure of 5 MPa, and the carbon dioxide inlet flow, the pressure difference between the inlet and outlet of the core to be measured is measured. At the beginning of displacement, CT scanning is performed every 120 seconds, and the pressure difference, the oil production and the gas production at the outlet are recorded every 10 minutes. After the gas is observed at the outlet of the core, CT scanning is performed every 40 minutes in the later stage of displacement, and CT scanning is performed every 100 minutes in the later stage of displacement. The CT values of the CT scanning at different time points in the displacement process are obtained.

[0083] (3) According to the gas-liquid data of the displacement outlet of the core to be measured in the displacement process, the carbon dioxide relative permeability of the displacement outlet of the core to be measured at each time point is calculated.

[0084] ​​The carbon dioxide saturation along the core at each moment was calculated based on the CT values ​​of the CT scans at different moments during the displacement process. The carbon dioxide saturation along the core at 60 min, 90 min, 180 min, and 270 min was obtained as follows: Figure 4 As shown;

[0085] According to the corresponding relationship between the carbon dioxide relative permeability and carbon dioxide saturation at the outlet of the core to be tested, the relationship curve between carbon dioxide saturation and relative permeability is obtained. The relationship curve is as follows: Figure 5 Middle K rg As shown, where K ro It represents the relative permeability of saturated oil.

[0086] (4) According to the relationship curve between carbon dioxide saturation and relative permeability, the relative permeability along the core to be tested is obtained from the carbon dioxide saturation along the core to be tested. The relative permeabilities along the core to be tested at 60 min, 90 min, 180 min and 270 min are as follows: Figure 6 shown.

[0087] (5) The amount of movable carbon dioxide along the core to be tested is calculated based on the relative permeability along the core. The amount of movable carbon dioxide along the core at 60 min, 90 min, 180 min and 270 min is as follows: Figure 7 As shown;

[0088] The difference between the gas intake and gas output of the core to be tested at each moment is the total amount of carbon dioxide retained inside the core to be tested. The bound carbon dioxide storage capacity at different moments is the difference between the total amount of carbon dioxide retained inside the core to be tested and the amount of movable carbon dioxide along the core.

[0089] Table 2

[0090] Carbon dioxide sequestered (mL) 60 min 0.33 90 min 0.36 180 min 0.38 270 min 0.42

[0091] In summary, the method provided by the present invention, combined with online CT scanning technology, can accurately derive the relationship curve between carbon dioxide saturation and relative permeability in the core based on core displacement experiments. This allows calculation of the amount of carbon dioxide retained and bound in the core at different times during the displacement process, thus enabling real-time dynamic observation of the carbon dioxide retention and binding during the carbon dioxide flooding and storage process.

[0092] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for measuring the dynamic amount of carbon dioxide sequestration in a carbon dioxide flooding oil reservoir, characterized by, The determination method comprises the following steps: (1) calculating the porosity of the measured core based on the core displacement experiment, and obtaining the measured core saturated with simulated oil; (2) CT scanning the measured core saturated with simulated oil to obtain the CT value as the initial state of the measured core, then performing carbon dioxide displacement on the measured core, and performing CT scanning at different time points of the displacement process to obtain the CT value at different time points of the displacement process; (3) calculating the carbon dioxide saturation along the path of the measured core and the carbon dioxide relative permeability at the displacement outlet at different time points, respectively, and drawing a relationship curve between the carbon dioxide saturation and the relative permeability of the measured core; (4) obtaining the carbon dioxide relative permeability along the path of the measured core at different time points according to the relationship curve; (5) calculating the carbon dioxide bound storage amount of the measured core at different time points.

2. The assay method according to claim 1, characterized by The process of calculating the porosity of the measured core based on the core displacement experiment in step (1) comprises: (a) vacuumizing the measured core, then saturating it with carbon dioxide, and performing CT scanning respectively to calculate the porosity distribution of the measured core; (b) vacuumizing the measured core, saturating it with water, and then displacing it with simulated oil, until the simulated oil displacement reaches the outlet of the measured core without water or the displacement multiple is more than 20 PV, to obtain the measured core saturated with simulated oil containing bound water.

3. The assay method according to claim 1 or 2, characterized in that, The calculation formula of the porosity is as follows: wherein, is the porosity; CT Satured is the CT value of the core to be measured saturated with carbon dioxide; CT Dry is the CT value of the dry core; CT Phase is the CT value of carbon dioxide; CT Air is the CT value of air.

4. Assay according to any one of claims 1 to 3, characterized in that The process of performing CT scanning at different time points of the displacement process in step (2) comprises: performing CT scanning once every 60-120 s after the displacement starts, and performing CT scanning once every 40-100 min after gas is observed at the displacement outlet of the measured core.

5. Assay according to any one of claims 1 to 4, characterized in that The calculation formula of the carbon dioxide relative permeability in step (3) is as follows: where K rg is the relative permeability of carbon dioxide; f o is the oil content; L is the length of the core; Q t is the total flow rate; μ o is the viscosity of the simulated oil; μ g is the viscosity of carbon dioxide; K is the absolute permeability of the core to be tested; A is the cross-sectional area of the core; Δp is the pressure difference between the two ends of the core; and V is the volume of fluid at the outlet.

6. Assay according to any one of claims 1 to 5, characterized in that The calculation formula of the carbon dioxide saturation in step (3) is as follows: where S Phase1 is the carbon dioxide saturation; is the porosity; CT Two is the CT value at any time during the displacement process; CT Satured2 is the CT value of the core to be tested saturated with the simulated oil; CT Phase1 is the CT value of the carbon dioxide; CT Phase2 is the CT value of the simulated oil.

7. Assay according to any one of claims 1 to 6, characterized in that The calculation process of the dynamic carbon dioxide bound storage amount in step (5) comprises: calculating the movable carbon dioxide amount along the path of the measured core according to the carbon dioxide relative permeability, and the carbon dioxide bound storage amount is the difference between the total amount of carbon dioxide retained in the measured core and the movable carbon dioxide amount along the path.

8. The assay method according to claim 7, characterized by The calculation formula of the movable carbon dioxide amount along the path is as follows: wherein Q i is the amount of mobile carbon dioxide along the path; K i is the relative permeability of carbon dioxide along the path; A is the cross-sectional area of the core; Δp is the pressure differential across the core; μ i is the viscosity of carbon dioxide at the current temperature and pressure; and L is the length of the core.

9. The assay method according to claim 7 or 8, characterized in that, The total amount of carbon dioxide retained in the measured core is the difference between the gas inlet amount and the gas outlet amount of the measured core during the displacement process.

10. Assay according to any one of claims 1 to 9, characterized in that, The determination method uses a non-steady-state displacement carbon dioxide retention amount testing device, and the non-steady-state displacement carbon dioxide retention amount testing device comprises a core holder connected with a displacement assembly, a differential pressure recording assembly, a CT scanner, a confining pressure pump, a phase separator, a back pressure pump and a temperature control assembly, respectively; The displacement assembly comprises an oil pump, a water pump and an intermediate container, the oil pump is connected to the core holder, and the water pump and the intermediate container are connected and connected to the core holder.

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