Experimental device for accurately simulating gas adsorption behavior of reservoir and use method of experimental device

Abstract

The invention discloses an experimental device for accurately simulating gas adsorption behavior of a reservoir and a use method thereof, the experimental device comprises an adsorption system, a gas supply system, a vacuum system and a data acquisition system, the adsorption system is used for placing a rock sample and simulating the actual working condition of the reservoir to perform an adsorption experiment; the gas supply system is used for supplying gas required by an experiment into the adsorption system; the vacuum system is used for vacuumizing internal devices and pipelines of the adsorption system to ensure the cleanliness of the system; and the data acquisition system is used for acquiring experimental data of the adsorption system and processing the experimental data. According to the invention, the high-temperature and high-pressure environment of the reservoir can be simulated, the adsorption process of gas in the porous medium can be accurately reproduced, and the real reservoir conditions can be better simulated, so that key data support is provided for reserve calculation of unconventional natural gas resources such as CBM (coalbed methane) and shale gas.

Description

Technical Field

[0001] The invention relates to an experimental device for accurately simulating reservoir gas adsorption behavior and a use method thereof, belonging to the technical field of natural gas development. Background Art

[0002] Natural gas development is inextricably linked to the gas transport mechanisms within reservoirs. Reservoir gas transport primarily involves adsorption, desorption, diffusion, and seepage. Adsorption is a crucial step in the transport process, and the adsorption capacity is a crucial parameter for assessing natural gas geological reserves. Therefore, accurately calculating the adsorption capacity of gas is fundamental for further exploring the adsorption characteristics and adsorption evolution of unconventional natural gas. It is also a crucial prerequisite for addressing a range of mine safety issues, such as coal and gas outbursts, and for promoting increased natural gas reserves and production. It is also of great significance in natural gas recovery, mine disaster management, and carbon dioxide geological storage.

[0003] The accuracy and reliability of test equipment have a direct impact on theoretical research, and improvements in theoretical research can also provide guidance for improving experimental equipment. To study the adsorption evolution of gases, a series of experimental apparatuses related to adsorption and diffusion have been developed based on different experimental requirements, and considerable research results have been achieved. In the field of gas adsorption, isothermal adsorption experiments based on gravimetric or volumetric methods are primarily used to determine the adsorption amount. To address the experimental difficulties and theoretical limitations of binary vapor adsorption, an automatic adsorption apparatus for measuring the individual adsorption isotherms of each component in binary vapor mixtures was developed [Development of Automatic Adsorption Apparatus for Binary Mixture: Measurement of Individual Adsorption Isotherms of Ethanol and Water from Their Mixed Vapors by Active Carbon Fiber]. This apparatus combines gravimetric and volumetric methods to measure the individual adsorption isotherms of each component in binary vapor mixtures without chemical analysis. The researchers also applied this apparatus to measure the adsorption isotherms of each component in a mixed vapor of ethanol and water, demonstrating that ethanol can be effectively separated from the mixed vapor using activated carbon fiber. In volumetric methods, estimating the free space volume is crucial for calculating adsorption. However, existing methods struggle to accurately estimate the free space volume. Therefore, a new volumetric gas adsorption apparatus (High Precision Volumetric Gas Adsorption Apparatus) has been developed that continuously measures the volume change of the free space to calculate gas adsorption, enabling highly accurate and repeatable adsorption measurements. This method is ideal for measuring samples with low surface areas.With the global carbon dioxide emissions increasing year by year, the application of carbon dioxide geological storage technology in deep unmineable coal seams has become one of the important ways to reduce carbon dioxide emissions and improve coalbed methane recovery [A review of coal properties pertinent to carbondioxide sequestration in coal seams: withspecial reference to Victorian browncoals] [Adsorption characteristics ofsupercritical carbon dioxide / CH4 on differenttypes of coal and a machine learning approach][Aminu MD, Nabavi SA,Rochelle CA, et al. A review of developments in carbon dioxide storage[J].Applied Energy, 2017, 208: 1389-1419.] [ Guan D,Gao P, Jiang Z, et al.Spatial evolution of carbon dioxide storage in depleted natural gas hydratereservoirs and its synergistic efficiency analysis[J]. Applied Energy, 2024,376: 124247.][Wang Y, Dai Z, Chen L, et al. An integrated multi-scale modelfor Carbon dioxide transport and storage in shale reservoirs[J]. Applied Energy, 2023, 331:120444.]. In order to reveal the influence mechanism of supercritical carbon dioxide on the pore structure and methane adsorption characteristics of coal, a supercritical fluid extraction device and microcalorimetry system were developed [Effects of supercritical carbon dioxide extraction on adsorption characteristics of methane on different types of coals].The device was used to study the adsorption behavior of methane on six coal samples treated with supercritical carbon dioxide, and the effects of supercritical extraction, coal rank and pressure on the methane adsorption amount, adsorption heat and pore structure were analyzed.

[0004] Traditional devices have facilitated the study of adsorption and diffusion behavior to a certain extent, laying the foundation for further improving natural gas recovery and addressing a series of problems that arise during the extraction process. However, they still have the following shortcomings: (1) The experimental operation is complicated and it is difficult to replace the sample. (2) The airtightness is not ideal and it is easy to leak when the experimental pressure is too high. (3) In order to improve the adsorption efficiency, the experimental devices in the past mostly used granular samples. However, this deviates from the conditions under in situ reservoir conditions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an experimental device for accurately simulating the adsorption behavior of reservoir gas and a method of using the same, so as to solve the technical problems existing in the above-mentioned prior art.

[0006] The technical solution adopted by the present invention is: an experimental device for accurately simulating the adsorption behavior of reservoir gas, including an adsorption system, a gas supply system, a vacuum system and a data acquisition system. The adsorption system is used to place rock samples and simulate the actual working conditions of the reservoir to conduct adsorption experiments; the gas supply system is used to supply the gas required for the experiment to the interior of the adsorption system; the vacuum system is used to vacuum the internal devices and pipelines of the adsorption system to ensure the cleanliness of the system; the data acquisition system is used to collect the experimental data of the adsorption system and process it.

[0007] Preferably, the adsorption system includes a standard chamber, a sample chamber and a triaxial compression system. The sample chamber includes a core holder, which is provided with a temperature measuring port and a ring pressure port. The temperature measuring port is installed with a temperature sensor for detecting the temperature inside the adsorption system, and the ring pressure port is provided with a pressure sensor for detecting the pressure inside the adsorption system. The temperature sensor and the pressure sensor are both electrically connected to the data acquisition system; a heating mechanism is provided inside the adsorption system.

[0008] Preferably, the gas supply system includes a He gas cylinder and a carbon dioxide gas cylinder, and the He gas cylinder and the carbon dioxide gas cylinder are both connected to the interior of the adsorption system through pipelines. Valves and pressure gauges are provided on the pipelines connecting the He gas cylinder and the carbon dioxide gas cylinder to the adsorption system. The carbon dioxide gas is used for adsorption experiments of the adsorption system, and the He gas is used to detect whether the adsorption system is leaking, flush the pipeline, and is also used as a reference gas when doing adsorption experiments.

[0009] Preferably, the vacuum system includes a vacuum pump, which is connected to the interior of the adsorption system through a pipeline, and the pipeline connecting the vacuum pump and the adsorption system is provided with a valve and a pressure gauge.

[0010] Preferably, the data acquisition system includes a control cabinet, a computer host and a display, the control cabinet is electrically connected to the computer host, and the computer host is electrically connected to the display; the adsorption system, the vacuum system and the air supply system are all electrically connected to the control cabinet; the operator sets the initial parameters of the temperature and pressure of the adsorption system through the computer host, and the computer host controls the adsorption system, the air supply system, the vacuum system and the data acquisition system to work automatically through the control cabinet, and then the system automatically completes the data collection and processing, and generates original data reports, analysis reports and related curve charts to intuitively display the instrument's workflow and experimental results.

[0011] A method for using an experimental device for accurately simulating reservoir gas adsorption behavior comprises the following steps: (1) Place the core sample in the core holder of the adsorption system sample chamber and check the air tightness of the adsorption system; (2) Calibrate the free space volume of the adsorption system; (3) Conduct adsorption test: ① Use the vacuum system to evacuate the interior of the adsorption system; ② Use the heating mechanism of the adsorption system to preheat the adsorption system to the experimental set temperature and maintain it; ③Open the gas source valve of the gas supply system cylinder and fill the adsorption system with adsorption gas to the experimental target pressure value; ④Open the isolation valve between the reference chamber and the sample chamber to allow the gas in the reference chamber to enter the sample chamber and begin adsorption; ⑤ Open the computer software of the data acquisition system and start collecting data with a cycle of 30 seconds. When there is no obvious change in pressure for more than 10 hours, it means that the adsorption has reached equilibrium. Then record the equilibrium pressure value; ⑥ Repeat steps ③, ④, and ⑤ until the end of the experiment.

[0012] Preferably, the specific steps of free space volume calibration are as follows: (1) Start the vacuum pump to evacuate the adsorption system for more than 0.5 h; (2) Loading the axial pressure and confining pressure to the set values ​​through the triaxial compression system; (3) Slowly fill the reference chamber with helium; (4) After the pressure stabilizes, record the pressure value in the reference chamber; (5) Open the valve connecting the reference chamber and the sample chamber, wait for the pressure to stabilize, and then record the pressure values ​​in the reference chamber and the sample chamber again; (6) Calculate the free space volume of the sample chamber based on the gas state equation and the principle of conservation of matter.

[0013] Beneficial effects of the present invention: 1. The experimental operation is simple and the sample can be easily replaced.

[0014] 2. The present invention adopts an electrically controlled pneumatic valve to replace the mechanical hand-controlled valve of the traditional device, which has the advantages of good switching performance, fast switching speed, high pressure resistance, and good sealing performance.

[0015] 3. The present invention comprehensively considers the influence of temperature field, stress field, etc. on gas adsorption and adsorption, and realizes the study of gas adsorption evolution law under multi-field coupling. The constant temperature system of the present invention is equipped with a columnar core holder that can withstand high temperature and high pressure, so as to better simulate real reservoir conditions.

[0016] 4. This invention plays a crucial role in the development and assessment of unconventional natural gas resources. It can simulate the high-temperature, high-pressure environment of reservoirs and accurately reproduce the gas adsorption process in porous media, providing key data support for the reserve calculation of unconventional natural gas resources such as coalbed methane (CBM) and shale gas. Furthermore, this invention can be used to study the transport characteristics of carbon dioxide in reservoirs, providing a scientific basis for evaluating the effectiveness of carbon dioxide geological storage. The experimental results obtained using this invention not only help optimize natural gas extraction strategies and improve recovery rates, but also provide a solid theoretical foundation for reserve assessment and rational resource development. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0018] The figure marks in the drawings of the specification include: vacuum system 10, vacuum pump 11, valve 12, pressure gauge 13, adsorption system 20, sample chamber 21, standard chamber 22, triaxial compression system 23, gas supply system 30, He gas cylinder 31, carbon dioxide gas cylinder 32, and pressure regulating valve 33. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0020] Example 1: An experimental device that accurately simulates the adsorption behavior of reservoir gases, such as Figure 1As shown, it includes an adsorption system 20, a gas supply system 30, a vacuum system 10 and a data acquisition system. The adsorption system 20 is used to place rock samples and simulate the actual working conditions of the reservoir to conduct adsorption experiments; the gas supply system 30 is used to supply the gas required for the experiment to the inside of the adsorption system 20; the vacuum system 10 is used to vacuum the internal devices and pipelines of the adsorption system 20 to ensure the cleanliness of the system; the data acquisition system is used to collect and process the experimental data of the adsorption system 20.

[0021] In this embodiment, Figure 1 As shown, the adsorption system 20 includes a standard chamber 22, a sample chamber 21 and a triaxial compression system 23. The standard chamber 22 is a reference chamber, the sample chamber 21 is used to place samples, and the triaxial compression system 23 is used to load axial pressure and confining pressure to simulate actual reservoir conditions.

[0022] In this embodiment, the sample chamber 21 includes a core holder, which is provided with a temperature measuring port and a ring pressure port. The temperature measuring port is installed with a temperature sensor for detecting the temperature inside the adsorption system 20, and the ring pressure port is provided with a pressure sensor for detecting the pressure inside the adsorption system 20. The temperature sensor and the pressure sensor are both electrically connected to the data acquisition system; a heating mechanism is provided inside the adsorption system 20, and the heating mechanism is an electric heating plate.

[0023] In this embodiment, two sets of core holders are provided: Φ25 × 25–100 mm (25 mm diameter, 25–100 mm height) and Φ50 × 50–100 mm (50 mm diameter, 50–100 mm height). The size is selected based on actual needs. The two sets of core holders are connected in parallel.

[0024] In this embodiment, the gas supply system 30 includes a He gas cylinder 31 and a carbon dioxide gas cylinder 32. The He gas cylinder 31 and the carbon dioxide gas cylinder 32 are both connected to the interior of the adsorption system 20 through pipelines. A valve 12 and a pressure gauge 13 are provided on the pipeline connecting the He gas cylinder 31 and the carbon dioxide gas cylinder 32 to the adsorption system 20. The carbon dioxide gas is used for the adsorption experiment of the adsorption system 20, and the He gas is used to detect whether the adsorption system 20 is leaking and to flush the pipeline. It is also used as a reference gas when doing adsorption experiments.

[0025] In this embodiment, the vacuum system 10 includes a vacuum pump 11 , which is connected to the interior of the adsorption system 20 via a pipeline. The pipeline connecting the vacuum pump 11 and the adsorption system 20 is provided with a valve 12 , a pressure gauge 13 and a pressure regulating valve 33 .

[0026] In this embodiment, the data acquisition system includes a control cabinet, a computer host and a display. The control cabinet is electrically connected to the computer host, and the computer host is electrically connected to the display; the adsorption system 20, the vacuum system 10 and the air supply system are all electrically connected to the control cabinet; the operator sets the initial parameters of the temperature and pressure of the adsorption system 20 through the computer host, and the host controls the adsorption system 20, the air supply system 30, the vacuum system 10 and the data acquisition system through the control cabinet to automatically operate. Then the system automatically completes the data collection and processing, and generates original data reports, analysis reports and related curve charts to intuitively display the instrument's workflow and experimental results.

[0027] In this embodiment, the maximum confining pressure provided by the manual pump of the adsorption system 20 is 60 MPa; the applicable core size of the adsorption system 20 is 80–100 mm; the lower limit of the operating temperature of the diffusion system is room temperature, and the upper limit is 120°C; the accuracy of the pressure sensor is 0.25%, and the pressure difference accuracy is 0.05%.

[0028] This embodiment also discloses a method for using an experimental device for accurately simulating reservoir gas adsorption behavior, including the following steps: (1) Place the cylindrical core sample into the core holder of the sample chamber 21 of the adsorption system 20 and perform an airtightness check on the adsorption system 20. To ensure that the system remains airtight at the highest experimental pressure, the gas pressure filled during the airtightness check must not be lower than the maximum experimental pressure. Observe continuously for 24 hours. If the pressure in the system remains basically stable, the system is considered to be airtight. Otherwise, refill the sample chamber 21 and recheck the airtightness.

[0029] (2) Calibrate the free space volume of the adsorption system 20. Since helium molecules are very small and do not undergo adsorption with coal, helium is usually used when calibrating the free space volume. The free space volume refers to the volume occupied by the free gas in the sample chamber 21, which mainly includes the sample void volume, the remaining sample chamber 21 volume excluding the sample, and the pipeline volume between the sample chamber 21 and the valve 12. According to the method of Guo et al. [Guo W, Xiong W, Gao S, et al. Isothermal adsorption / desorption characteristics of shale gas[J]. Journal of CentralSouth University (Science and Technology), 2013, 44(7): 2836-2840.], the free space volume of the sample chamber 21 is equal to the difference between the volume of the sample chamber 21 and the sample skeleton volume.

[0030] In this embodiment, the specific steps of free space volume calibration are as follows: ① Start the vacuum pump 11 to evacuate the adsorption system 20 for more than 0.5 hours. The vacuum system 10 consists of a VP750-30L vacuum pump 11, a vacuum valve, and a vacuum hose. Before each experiment or cyclic experiment, the system must be used to evacuate the experimental device and its pipelines for at least 0.5 hours to remove contaminants in the pipelines. The vacuuming time can be adjusted appropriately according to the sample size and gas type, but it must not exceed 5 hours. During the specific operation, the vacuum valve should be opened first to allow the vacuum pump 11 to circulate and extract the gas inside the system, and then the impurities should be discharged from the pump through the vent valve to ensure the cleanliness of the system. This process follows the following steps: The vacuum valve is activated to allow the vacuum pump 11 to be connected to the system.

[0031] The vacuum pump 11 starts working to circulate and extract the gas in the system.

[0032] Operate the vent valve in a timely manner to discharge the gas containing impurities out of the system to ensure that the impurities do not flow back.

[0033] Monitor the vacuum until the desired vacuum level for the experiment is reached.

[0034] ② The axial pressure and confining pressure are loaded to the set values ​​through the triaxial compression system 23. The loading order is to add the confining pressure first and then the axial pressure. The unloading order is the opposite of the loading order. ③ Slowly fill the reference chamber with helium; ④ After the pressure stabilizes, record the pressure value in the reference chamber; ⑤ Open the valve 12 connecting the reference chamber and the sample chamber 21, and record the pressure values ​​in the reference chamber and the sample chamber 21 again after the pressure stabilizes; ⑥ Calculate the free space volume of the sample chamber 21 based on the gas state equation and the principle of conservation of matter.

[0035] (3) Conduct adsorption test: ① Using the vacuum system 10 to evacuate the interior of the adsorption system 20; ② Using the heating mechanism of the adsorption system 20 to preheat the adsorption system 20 to the experimental set temperature and maintain it; ③ Open the gas supply system 30 and the gas source valve of the He gas cylinder 31 to fill the adsorption gas into the adsorption system 20 to the experimental target pressure value; ④ Open the isolation valve between the reference chamber and the sample chamber 21 to allow the gas in the reference chamber to enter the sample chamber 21 and begin adsorption; ⑤ Open the computer software of the data acquisition system and start collecting data with a cycle of 30 seconds. When there is no obvious change in pressure for more than 10 hours, it means that the adsorption has reached equilibrium. Then record the equilibrium pressure value; ⑥ Repeat steps ③, ④, and ⑤ until the end of the experiment.

[0036] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An experimental device for accurately simulating reservoir gas adsorption behavior, characterized by: It includes an adsorption system, an air supply system, a vacuum system and a data acquisition system. The adsorption system is used to place rock samples and simulate the actual working conditions of the reservoir to conduct adsorption experiments; the air supply system is used to supply the gas required for the experiment to the inside of the adsorption system; the vacuum system is used to vacuum the internal devices and pipelines of the adsorption system to ensure the cleanliness of the system; the data acquisition system is used to collect and process the experimental data of the adsorption system.

2. The experimental device for accurately simulating reservoir gas adsorption behavior according to claim 1, characterized in that: The adsorption system includes a standard chamber, a sample chamber and a triaxial compression system. The sample chamber includes a core holder. The core holder is provided with a temperature measuring port and a ring pressure port. The temperature measuring port is installed with a temperature sensor for detecting the temperature inside the adsorption system. The ring pressure port is provided with a pressure sensor for detecting the pressure inside the adsorption system. The temperature sensor and the pressure sensor are both electrically connected to the data acquisition system; a heating mechanism is provided inside the adsorption system.

3. The experimental device for accurately simulating reservoir gas adsorption behavior according to claim 1, characterized in that: The gas supply system includes a He gas cylinder and a carbon dioxide gas cylinder, both of which are connected to the interior of the adsorption system through pipelines. Valves and pressure gauges are provided on the pipelines connecting the He gas cylinder and the carbon dioxide gas cylinder to the adsorption system. The carbon dioxide gas is used for adsorption experiments of the adsorption system, and the He gas is used to detect whether the adsorption system is leaking and to flush the pipeline. It is also used as a reference gas when doing adsorption experiments.

4. The experimental device for accurately simulating reservoir gas adsorption behavior according to claim 1, characterized in that: The vacuum system includes a vacuum pump, which is connected to the interior of the adsorption system through a pipeline. The pipeline connecting the vacuum pump and the adsorption system is provided with a valve and a pressure gauge.

5. The experimental device for accurately simulating reservoir gas adsorption behavior according to claim 1, characterized in that: The data acquisition system includes a control cabinet, a computer host and a display. The control cabinet is electrically connected to the computer host, and the computer host is electrically connected to the display. The adsorption system, the vacuum system and the air supply system are all electrically connected to the control cabinet. The operator sets the initial parameters of the temperature and pressure of the adsorption system through the computer host, and the computer host controls the adsorption system, the air supply system, the vacuum system and the data acquisition system to work automatically through the control cabinet. Then the system automatically completes data collection and processing, and generates original data reports, analysis reports and related curve charts to intuitively display the instrument's workflow and experimental results.

6. A method for using the experimental device for accurately simulating reservoir gas adsorption behavior according to any one of claims 1 to 5, characterized in that: The following steps are involved: Place the cylindrical core sample into the core holder of the sample chamber of the adsorption system and check the air tightness of the adsorption system; Calibrate the free space volume of the adsorption system; Conduct adsorption test: ① Use the vacuum system to evacuate the interior of the adsorption system; ② Use the heating mechanism of the adsorption system to preheat the adsorption system to the experimental set temperature and maintain it; ③Open the gas source valve of the gas supply system cylinder and fill the adsorption system with adsorption gas to the experimental target pressure value; ④Open the isolation valve between the reference chamber and the sample chamber to allow the gas in the reference chamber to enter the sample chamber and begin adsorption; ⑤ Open the computer software of the data acquisition system and start collecting data with a cycle of 30 seconds. When there is no obvious change in pressure for more than 10 hours, it means that the adsorption has reached equilibrium. Then record the equilibrium pressure value; ⑥ Repeat steps ③, ④, and ⑤ until the end of the experiment.

7. The method for using the experimental device for accurately simulating reservoir gas adsorption behavior according to claim 6, characterized in that: The specific steps for free space volume calibration are as follows: (1) Start the vacuum pump to evacuate the adsorption system for more than 0.5 h; (2) Loading the axial pressure and confining pressure to the set values ​​through the triaxial compression system; (3) Slowly fill the reference chamber with helium; (4) After the pressure stabilizes, record the pressure value in the reference chamber; (5) Open the valve connecting the reference chamber and the sample chamber, wait for the pressure to stabilize, and then record the pressure values ​​in the reference chamber and the sample chamber again; (6) Calculate the free space volume of the sample chamber based on the gas state equation and the principle of conservation of matter.

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