Device and method for visually monitoring migration and diffusion of CO2 injected into edge-bottom water gas reservoir

Abstract

The invention belongs to the technical field of gas field development and research, and discloses a device and method for visually monitoring migration and diffusion of CO2 injected into an edge-bottom water gas reservoir, and the device comprises a high-pressure piston container and an online nuclear magnetic clamp; a lower end interface of the high-pressure piston container is connected with the high-pressure ISCO injection pump, and an upper end interface of the high-pressure piston container is connected with an injection port of the on-line nuclear magnetic holder; an extraction port of the on-line nuclear magnetic holder is connected with the back-pressure valve, the back-pressure valve is connected with the gas-liquid separator, and the gas-liquid separator is respectively connected with the liquid metering device, the weighing device and the gas metering device; the upper end of the on-line nuclear magnetic holder is connected with the high-temperature and high-pressure circulating system, and covering pressure is provided for the on-line nuclear magnetic holder. The experimental pressure and temperature are accurately controlled, migration of CO2 in the edge-bottom water gas reservoir is truly simulated, the seepage condition of CO2 in a rock core is visualized in combination with online nuclear magnetic equipment, and certain guidance and technical support are provided for CO2 injection to improve the recovery efficiency of the edge-bottom water gas reservoir.

Description

Technical Field

[0001] This invention relates to the field of gas field development and research technology, specifically to a device and method for visually monitoring the migration and diffusion of CO2 injected into edge and bottom water gas reservoirs. Background Technology

[0002] During the development of edge-water gas reservoirs, as the reservoir pressure gradually decreases, edge water continuously intrudes into the gas-bearing area, forming a two-phase flow of gas and water in the reservoir. This reduces the gas phase flow capacity, causing a rapid decline in single-well productivity. Simultaneously, as water intrusion intensifies, water gradually penetrates to the bottom of the well, leading to a surge in the wellbore fluid level, increased abandonment pressure, and the sealing of a large amount of gas in the reservoir, reducing the gas recovery rate. The recovery rate of waterless gas reservoirs is usually above 80%, while the recovery rate of water-intruded gas reservoirs is usually below 40%. Moreover, when the low gas phase flow velocity in the wellbore cannot provide sufficient energy to carry out the liquid accumulated at the bottom of the well, drainage and other operations are required, increasing production costs.

[0003] Supercritical CO2 has a density close to that of a liquid and a viscosity close to that of a gas. Injecting CO2 can effectively replenish the energy of a gas reservoir and enhance its flow capacity. Furthermore, it can form slugs to prevent the intrusion of edge and bottom water. Therefore, conducting experiments on CO2 migration and diffusion in edge and bottom water gas reservoirs is of significant guiding importance for understanding the microscopic seepage mechanism and improving the recovery rate of edge and bottom water gas reservoirs. [1-3] .

[0004] Current experiments on CO2 migration and diffusion in edge-bottom water-gas reservoirs mainly employ core holders for displacement experiments. However, these experiments can only monitor the breakthrough time of CO2 migration and diffusion, making it difficult to realize the dynamic migration patterns of CO2 within the core and its distribution characteristics in different microscopic pore throats. Therefore, this paper designs an experimental device and method for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs, enabling real-time visual monitoring of CO2 migration and diffusion during these processes.

[0005] CN116877054A discloses a carbon dioxide displacement simulation experimental device with the following structure: a nitrogen source pipeline is connected to a core holder, and the displacement pump and piston cylinder pipeline are connected to the inlet end of the core holder. The carbon dioxide source is connected in parallel to both the pipeline connecting the displacement pump to the core holder and the pipeline connecting the nitrogen source to the core holder. Carbon dioxide is mixed separately with both gas and liquid before being used in the displacement experiment. After assembling the experimental device once, it can simulate displacement processes under different conditions such as carbon dioxide displacement alone, gas mixed displacement, and reverberant displacement, according to experimental needs, without the need for separate experimental setups, effectively saving labor costs and having a wide range of applications. However, this technical solution still cannot solve the aforementioned technical problems.

[0006] [1] Yang Dongsheng, Xie Kun, Yin Qingguo, et al. Current status and prospect of research on water intrusion patterns in edge-bottom water gas reservoirs [J]. Natural Gas Geoscience, 2024, 35(07):1304-1322.

[0007] [2] Hou Dali, Gong Fengming, Chen Bo, et al. Mechanism and storage effect of CO2 injection to enhance oil recovery in bottom water sandstone gas reservoirs [J]. Natural Gas Industry, 2024, 44(04): 93-103.

[0008] [3] Li Yang, Huang Wenhuan, Jin Yong, et al. Development and application of CO2 flooding enhanced oil recovery technology for different reservoir types in Sinopec under the dual carbon vision [J]. Oil and Gas Reservoir Evaluation and Development, 2021, 11(06):793-804+790. Summary of the Invention

[0009] The purpose of this invention is to provide a device and method for visually monitoring the migration and diffusion of CO2 in edge-bottom water-gas reservoirs, so as to realize the monitoring of the dynamic migration process of CO2 in the core, better understand the microscopic seepage mechanism of CO2 migration and diffusion in edge-bottom water-gas reservoirs, and provide certain guidance for improving the recovery rate of CO2 injection in edge-bottom water-gas reservoirs.

[0010] A device for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs includes a high-pressure piston container and an online nuclear magnetic resonance (NMR) clamp. The lower interface of the high-pressure piston container is connected to a high-pressure ISCO injection pump, and the upper interface is connected to the injection port of the online NMR clamp. The production port of the online NMR clamp is connected to a backpressure valve, which is connected to a gas-liquid separator. The gas-liquid separator is connected to a liquid metering device, a weighing device, and a gas metering device, respectively. The upper end of the online NMR clamp is connected to a high-temperature and high-pressure circulation system to provide pressure for the online NMR clamp.

[0011] Furthermore, the gas metering device is a chromatograph.

[0012] Furthermore, the high-temperature and high-pressure circulation system consists of: a confining pressure tracking pump, a circulation pump, a heat exchanger, and a temperature circulation system.

[0013] Furthermore, the online NMR holder contains a core sample, with the left side designated as the injection port and the right side as the extraction port.

[0014] Furthermore, the high-pressure piston container is configured as three: high-pressure piston container A, high-pressure piston container B, and high-pressure piston container C.

[0015] Furthermore, high-pressure piston container A is filled with H2O, high-pressure piston container B is filled with CH4, and high-pressure piston container C is filled with CO. 2。

[0016] A method for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs includes the following steps:

[0017] (1) The pretreated core was placed in an online nuclear magnetic resonance holder and the original formation water T2 spectrum was tested;

[0018] (2) Open valve V8, start confining pressure tracking pump 8, set pressure difference, apply confining pressure, and heat the system temperature to the formation temperature through the temperature circulation system;

[0019] (3) Open valves V2, V5, V7, and V9, and start the high-pressure ISCO injection pump to displace the core to the bound water saturation level;

[0020] (4) Open valve V10, start the back pressure control pump, set the back pressure valve pressure to the formation pressure, saturate the core with methane to the formation pressure, and simulate the gas reservoir charging process.

[0021] (5) Close valves V2 and V5, open valves V1 and V4, and gradually reduce the pressure of the back pressure valves until the pressure is abandoned by the back pressure control pump to simulate the water invasion process of the gas reservoir. At the same time, monitor the water invasion process and the degree of production by online nuclear magnetic resonance.

[0022] (6) Close valves V1 and V4, open valves V3 and V6, control the injection pressure and injection volume of CO2 through the high-pressure ISCO injection pump, monitor the T2 spectrum in real time through online nuclear magnetic resonance equipment, analyze the distribution characteristics of CO2 in different pore throats, and determine the gas-water distribution at different locations based on the layered T2 spectrum and nuclear magnetic resonance imaging.

[0023] (7) The CO2 breakthrough time and the composition of the produced gas are monitored in real time by a gas phase metering device at the outlet end. By comparing the layered T2 spectrum and nuclear magnetic resonance imaging at different times, the CO2 diffusion coefficient is calculated, and the visualization monitoring of CO2 migration and diffusion in the bottom water gas reservoir is realized.

[0024] Further pretreatment includes cleaning and drying the reservoir core, testing the core porosity and permeability, placing the core into a saturation device, and using formation water to vacuum saturate the core.

[0025] Furthermore, the saturation time is generally 20-30 hours.

[0026] Furthermore, the pressure difference is typically 5-10 MPa.

[0027] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0028] This invention innovatively designs a method and device for visually monitoring the migration and diffusion of CO2 in edge-bottom water-gas reservoirs. It precisely controls the experimental pressure and temperature, realistically simulates the migration of CO2 in edge-bottom water-gas reservoirs, and, combined with online NMR equipment, visualizes the seepage of CO2 in the core, providing guidance and technical support for improving the recovery rate of edge-bottom water-gas reservoirs through CO2 injection.

[0029] An experimental apparatus and method for visually monitoring CO2 migration and diffusion in edge-bottom water gas reservoirs utilizes real-time T2 spectra, layered T2 spectra, and NMR imaging capabilities of online NMR to perform real-time visual monitoring of gas-water distribution in core samples. This allows for observation of the dynamic migration patterns of CO2 within the core and its distribution characteristics in different microscopic pore throats. At the outlet end, gas chromatography is used to monitor the CO2 breakthrough time and produced gas composition in real time. By comparing layered T2 spectra and NMR imaging at different times, the CO2 diffusion coefficient is calculated, achieving visual monitoring of CO2 migration and diffusion in edge-bottom water gas reservoirs. Compared to traditional thermo-barrier systems, this apparatus and method, through a gas booster pump and temperature circulation system, allows for more convenient and precise control of experimental pressure and temperature, simulating the real-world CO2 flooding situation in edge-bottom water gas reservoirs. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0031] Figure 1 This is a schematic diagram of the structure of the present invention.

[0032] The attached diagram lists the components represented by each number as follows:

[0033] 1. High-pressure piston container A, 2. High-pressure piston container B, 3. High-pressure piston container C, 4. High-pressure ISCO injection pump, 5. Heat exchanger, 6. Temperature circulation system, 7. Circulation pump, 8. Confining pressure tracking pump, 9. Online NMR clamp, 10. Pressure sensor, 11. Data acquisition unit, 12. Computer, 13. Back pressure control pump, 14. Back pressure valve, 15. Gas-liquid separator, 16. Weighing device, 17. Gas metering device. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0035] Example 1

[0036] This invention presents a self-designed device for visually monitoring the migration and diffusion of CO2 in edge-bottom water-gas reservoirs, comprising a high-pressure piston container and an online NMR holder 9; the lower end of the high-pressure piston container is connected to a high-pressure ISCO injection pump 4, and the upper end is connected to the injection port of the online NMR holder 9; the production port of the online NMR holder 9 is connected to a backpressure valve 14, which is connected to a gas-liquid separator 15, which is connected to a liquid metering device, a weighing device 16, and a chromatograph; the upper end of the online NMR holder 9 is connected to a high-temperature and high-pressure circulation system to provide pressure for the online NMR holder 9.

[0037] The high-temperature and high-pressure circulation system consists of: a confining pressure tracking pump 8, a circulation pump 7, a heat exchanger 5, and a temperature circulation system 6.

[0038] The online NMR holder 9 contains a core sample, with the left side designated as the injection port and the right side as the extraction port. Furthermore, three high-pressure piston containers are configured: high-pressure piston container A1, high-pressure piston container B2, and high-pressure piston container C3. High-pressure piston container A1 contains H2O, high-pressure piston container B2 contains CH4, and high-pressure piston container C3 contains CO. 2。

[0039] Example 2

[0040] The specific experimental procedures are as follows:

[0041] (1) Clean and dry the reservoir core;

[0042] (2) Test the porosity and permeability of the core sample;

[0043] (3) The core was placed in the overburden saturation device and the formation water was used to vacuum overburden saturation for 24 hours;

[0044] (4) Place the core into the online NMR holder 9 and test the original formation water T2 spectrum;

[0045] (5) Open valve V8, start confining pressure tracking pump 13, set pressure difference (5MPa), apply confining pressure, and heat the system temperature to the formation temperature through temperature circulation system 6;

[0046] (6) Open valves V2, V5, V7, and V9, and start the high-pressure ISCO injection pump 4 to displace the core to the bound water saturation level;

[0047] (7) Open valve V10, start back pressure control pump 13, set back pressure valve 14 to formation pressure, saturate core with methane to formation pressure, and simulate gas reservoir charging process.

[0048] (8) Close valves V2 and V5, open valves V1 and V4, and gradually reduce the pressure of back pressure valve 14 until the abandoned pressure through back pressure control pump 13 to simulate the water invasion process of the gas reservoir. At the same time, monitor the water invasion process and the degree of production through online nuclear magnetic resonance.

[0049] (9) Close valves V1 and V4, open valves V3 and V6, control the injection pressure and injection volume of CO2 through high-pressure ISCO injection pump 4, monitor the T2 spectrum in real time through online nuclear magnetic resonance equipment, analyze the distribution characteristics of CO2 in different pore throats, and determine the gas-water distribution at different locations based on the layered T2 spectrum and nuclear magnetic resonance imaging.

[0050] (10) The CO2 breakthrough time and the composition of the produced gas are monitored in real time by a chromatograph at the outlet end. By comparing the layered T2 spectrum and nuclear magnetic resonance imaging at different times, the CO2 diffusion coefficient is calculated, and the visualization monitoring of CO2 migration and diffusion in the bottom water gas reservoir is realized.

[0051] The above are merely preferred embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions, or improvements made to the technical solutions described in the foregoing embodiments, or to some of the technical features, shall fall within the protection scope of the present invention.

[0052] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

Claims

1. A device for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs, characterized in that, It includes a high-pressure piston container and an online nuclear magnetic resonance (NMR) clamp (9); the lower end of the high-pressure piston container is connected to a high-pressure ISCO injection pump (4), and the upper end is connected to the injection port of the online NMR clamp (9); the extraction port of the online NMR clamp (9) is connected to a back pressure valve (14), the back pressure valve (14) is connected to a gas-liquid separator (15), the gas-liquid separator (15) is connected to a liquid metering device, a weighing device (16) and a gas metering device (17) respectively; the upper end of the online NMR clamp (9) is connected to a high-temperature and high-pressure circulation system.

2. The device for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs according to claim 1, characterized in that, The gas metering device (17) is a chromatograph.

3. The device for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs according to claim 1, characterized in that, The high-temperature and high-pressure circulation system consists of: a confining pressure tracking pump (8), a circulation pump (7), a heat exchanger (5), and a temperature circulation system (6).

4. The device for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs according to claim 1, characterized in that, The online nuclear magnetic resonance holder (9) contains a core sample, with the left side designated as the injection port and the right side as the extraction port.

5. The device for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs according to claim 1, characterized in that, The high-pressure piston container is configured as three: high-pressure piston container A (1), high-pressure piston container B (2), and high-pressure piston container C (3).

6. The device for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs according to claim 5, characterized in that, High-pressure piston container A(1) contains H2O, high-pressure piston container B(2) contains CH4, and high-pressure piston container C(3) contains CO. 2。 7. A method for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs, characterized in that, Includes the following steps: (1) The pretreated core was placed in an online nuclear magnetic resonance holder and the original formation water T2 spectrum was tested; (2) Open valve V8, start confining pressure tracking pump (8), set pressure difference, apply confining pressure, and heat the system temperature to the formation temperature through temperature circulation system (6); (3) Open valves V2, V5, V7, and V9, and start the high-pressure ISCO injection pump (4) to displace the core to the bound water saturation level; (4) Open valve V10, start back pressure control pump (13), set back pressure valve (14) pressure to formation pressure, saturate core with methane to formation pressure, and simulate gas reservoir charging process; (5) Close valves V2 and V5, open valves V1 and V4, and gradually reduce the pressure of back pressure valve (14) until the abandoned pressure through back pressure control pump (13) to simulate the water invasion process of the gas reservoir. At the same time, monitor the water invasion process and the degree of production through online nuclear magnetic resonance. (6) Close valves V1 and V4, open valves V3 and V6, control the injection pressure and injection volume of CO2 through the high-pressure ISCO injection pump (4), monitor the T2 spectrum in real time through online nuclear magnetic resonance equipment, analyze the distribution characteristics of CO2 in different pore throats, and determine the gas-water distribution at different locations based on the layered T2 spectrum and nuclear magnetic resonance imaging. (7) The CO2 breakthrough time and the composition of the produced gas are monitored in real time by a gas phase metering device at the outlet end. By comparing the layered T2 spectrum and nuclear magnetic resonance imaging at different times, the CO2 diffusion coefficient is calculated, and the visualization monitoring of CO2 migration and diffusion in the bottom water gas reservoir is realized.

8. The method for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs according to claim 1, characterized in that, The pretreatment in step (1) includes cleaning and drying the reservoir core, testing the core porosity and permeability, placing the core into the overburden saturation device, and using formation water to vacuum overburden saturation.

9. The method for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs according to claim 8, characterized in that, The time for saturation by pressure covering is 20-30 hours.

10. The method for visually monitoring CO2 migration and diffusion in edge-bottom water-gas reservoirs according to claim 1, characterized in that, The pressure difference in step (2) is 5-10 MPa.

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