Gas-water-coal powder multiphase percolation experiment device and method

Abstract

This application provides an experimental apparatus and method for gas-water coal powder multiphase flow. The experimental apparatus includes: an inlet end, a liquid inlet end, an outlet end, a liquid outlet end, a coal reservoir simulation device, and a gas-liquid separation device. A gas-water coal powder multiphase fluid formed by coal powder water and medium gas is injected into the coal reservoir simulation device, and then separated into coalbed methane and liquid by the gas-liquid separation device. A first valve and a second valve are respectively installed at the inlet end and the liquid inlet end. First, second, third, and fourth pressure gauges measure the pressure at the inlet end, the liquid inlet end, the outlet end, and the liquid outlet end, respectively. Coal powder water of different concentrations is prepared, and each preset concentration of coal powder water is added to the coal reservoir simulation device in each experiment. The first and second valves are adjusted to regulate the flow rate at the inlet end and the liquid inlet end, resulting in coal powder water with different saturations. This yields phase permeation curves of coal powder water with different concentrations based on different preset saturations. This allows for the quantitative simulation of coal powder production dynamics in coal reservoirs, the study of gas-water production characteristics within coal reservoir cleavages, and thus guidance for coalbed methane reservoir drainage processes.

Description

Technical Field

[0001] This application relates to the field of coalbed methane geological engineering technology, specifically to a gas-water-coal powder multiphase flow experimental device and method. Background Technology

[0002] Unlike conventional oil and gas reservoirs, coalbed methane (CBM) reservoirs experience significant coal dust production during extraction. CBM reservoirs possess a dual-media system of matrix and cleavage, and the drainage process is consistently a two-phase flow (gas-liquid) stage, resulting in substantial coal dust production. Multiphase flow of coalbed methane, water, and coal dust is the norm during CBM drainage. Therefore, studying the phase permeability curves under multiphase flow of coalbed methane, water, and coal dust is crucial for understanding the production dynamics of CBM reservoirs and guiding the drainage process. However, current experimental methods cannot quantitatively simulate the dynamics of coal dust production in coal reservoirs, thus hindering the simulation of multiphase flow of coalbed methane, water, and coal dust and the testing of phase permeability curves. Summary of the Invention

[0003] The purpose of this application is to provide an experimental apparatus and method for gas-water-coal powder multiphase flow.

[0004] To achieve the above objectives, the first aspect of this application provides a gas-water-pulverized coal multiphase flow experimental apparatus, comprising: The air inlet is connected to the first end of the coal reservoir simulation device and is used to inject medium gas into the coal reservoir simulation device. The liquid inlet end is connected to the first end and is used to inject pulverized coal water into the coal reservoir simulation device. A coal reservoir simulation device is used to simulate the dynamic process of pulverized coal, water, and gas flowing together through the coal reservoir simulation device. A gas-liquid separation device, connected to a coal reservoir simulation device, is used to separate the gas-water-coal powder multiphase fluid flowing out of the coal reservoir simulation device into coalbed methane and coal powder-containing liquid. The gas outlet is connected to the second end of the gas-liquid separator, and coalbed methane flows out from the gas outlet. The liquid outlet end is connected to the second end, and the liquid flows out from the liquid outlet end; The first valve is located between the air inlet end and the first end, and is used to regulate the gas flow rate at the air inlet end; The second valve is located between the inlet end and the first end and is used to regulate the liquid flow rate at the inlet end. The first pressure gauge is installed between the first valve and the first end to detect the first pressure of the gas at the inlet end; The second pressure gauge is installed between the second valve and the first end to detect the second pressure of the liquid at the inlet end; The third pressure gauge is located between the second end and the outlet end and is used to detect the third pressure of the gas at the outlet end. The fourth pressure gauge is located between the second end and the outlet end and is used to detect the fourth pressure of the liquid at the outlet end.

[0005] In embodiments of this application, the experimental apparatus further includes: a first flow meter disposed between the first valve and the first end, for detecting the gas flow rate at the inlet end; a second flow meter disposed between the second valve and the first end, for detecting the liquid flow rate at the liquid inlet end; a third flow meter disposed between the liquid outlet end and the second end, for detecting the liquid flow rate at the liquid outlet end; and a fourth flow meter disposed between the gas outlet end and the second end, for detecting the gas flow rate at the gas outlet end.

[0006] In the embodiments of this application, the experimental apparatus further includes: a gas supply device, disposed at the gas inlet end, for supplying gas to the coal reservoir simulation device; a stirring device, disposed at the liquid inlet end, for stirring coal powder water; a gas collection device, disposed at the gas outlet end, for collecting coalbed gas discharged from the gas-liquid separation device; and a liquid collection device, disposed at the liquid outlet end, for collecting liquid discharged from the gas-liquid separation device.

[0007] In the embodiments of this application, the experimental apparatus further includes: a third valve, disposed at the first end, wherein when the third valve is opened, pulverized coal water and medium gas enter the coal reservoir simulation device; a fourth valve, disposed at the second end, wherein when the fourth valve is opened, gas-water-pulverized coal multiphase fluid flows out of the coal reservoir simulation device; a fifth valve, disposed at the gas outlet end, wherein when the fifth valve is opened, coalbed methane flows out from the gas outlet end; and a sixth valve, disposed at the liquid outlet end, wherein when the sixth valve is opened, liquid flows out from the liquid outlet end.

[0008] A second aspect of this application provides a multiphase flow test method for gas-water-pulverized coal, applied to a multiphase flow test apparatus for gas-water-pulverized coal, the method comprising: Multiple preset concentrations of pulverized coal water are prepared, and each preset concentration of pulverized coal water is added to the coal reservoir simulation device through the inlet end in sequence. For each preset concentration of pulverized coal water, adjust the first valve and the second valve to ensure that the saturation of the preset concentration of pulverized coal water reaches the preset saturation level. For each preset concentration of pulverized coal water, determine the relative permeability of the water phase and the relative permeability of the gas phase at each preset saturation level; For each preset concentration of pulverized coal water, the relative permeability curves of pulverized coal water at the preset concentration based on different preset saturations are determined according to multiple gas phase relative permeability and water phase relative permeability of pulverized coal water at the preset concentration.

[0009] In the embodiments of this application, determining the relative permeability of the aqueous phase and the relative permeability of the gas phase of pulverized coal water at each preset saturation level for each preset concentration includes: for each preset concentration of pulverized coal water, when the liquid flow rate at the inlet end is the same as the liquid flow rate at the outlet end, and the gas flow rate at the inlet end is the same as the gas flow rate at the outlet end, the first pressure at the inlet end, the second pressure at the inlet end, the third pressure at the outlet end, and the fourth pressure at the outlet end of the pulverized coal water at each preset saturation level are obtained by using a first pressure gauge, a second pressure gauge, a third pressure gauge, and a fourth pressure gauge, respectively; for each preset concentration of pulverized coal water, determining the relative permeability of the aqueous phase and the relative permeability of the gas phase of the pulverized coal water at each preset saturation level based on the first pressure, the second pressure, the third pressure, and the fourth pressure.

[0010] In the embodiments of this application, determining the relative permeability of the aqueous phase and the relative permeability of the gas phase of pulverized coal water at each preset saturation level based on a first pressure, a second pressure, a third pressure, and a fourth pressure includes: determining the effective permeability of the aqueous phase of pulverized coal water at each preset saturation level based on a second pressure and a fourth pressure; determining the effective permeability of the gas phase of pulverized coal water at each preset saturation level based on a first pressure and a third pressure; determining the absolute permeability of pulverized coal water at each preset concentration; and determining the relative permeability of the aqueous phase of pulverized coal water at each preset saturation level based on the ratio between the effective permeability of the aqueous phase and the absolute permeability, and determining the relative permeability of the gas phase of pulverized coal water at each preset saturation level based on the ratio between the effective permeability of the gas phase and the absolute permeability.

[0011] In the embodiments of this application, for each preset concentration of pulverized coal water, determining the effective permeability of the aqueous phase at each preset saturation level based on the second pressure and the fourth pressure includes calculating the effective permeability of the aqueous phase according to the following formula (1): (1) in, This refers to the effective permeability of the aqueous phase in pulverized coal water. This refers to the preset saturation level of the pulverized coal water. This refers to the viscosity of the coal powder water. This refers to the length of the coal reservoir simulation device. This refers to the flow rate of liquid entering the coal reservoir simulation device at the inlet end. This refers to the cross-sectional area of ​​the coal reservoir simulation device. It refers to the pressure difference between the fourth pressure and the second pressure.

[0012] In the embodiments of this application, determining the effective gas-phase permeability of pulverized coal water at each preset saturation level based on the first pressure and the third pressure for each preset concentration of pulverized coal water includes: determining the gas viscosity and deviation coefficient of the experimental device based on the arithmetic mean of the first pressure and the third pressure for each preset concentration of pulverized coal water; obtaining the device parameters of the coal reservoir simulation device, including the device cross-sectional area and device length; and determining the effective gas-phase permeability of pulverized coal water at each preset saturation level for each preset concentration of pulverized coal water based on the device parameters, gas viscosity, deviation coefficient, first pressure, and third pressure.

[0013] In the embodiments of this application, for each preset concentration of pulverized coal water, determining the relative permeability of the gas phase of the pulverized coal water at each preset saturation level based on device parameters, gas viscosity, deviation coefficient, first pressure, and third pressure includes calculating the relative permeability of the gas phase according to the following formula (2): (2) in, This refers to the effective gas-phase permeability of pulverized coal water. This refers to the preset saturation level of the pulverized coal water. This refers to standard atmospheric pressure. This refers to the gas flow rate entering the coal reservoir simulation device at the inlet end. This refers to the gas viscosity of coalbed methane under average pressure in a coal reservoir simulation device. This refers to the length of the coal reservoir simulation device. This refers to the cross-sectional area of ​​the coal reservoir simulation device. The deviation coefficient of coalbed methane in a coal reservoir simulation device under average pressure, where average pressure refers to the arithmetic mean of the first and third pressures. This refers to the first pressure. It refers to the third pressure.

[0014] The above-described gas-water-coal powder multiphase flow experimental device and method are used. The experimental device includes: an inlet end, a liquid inlet end, an outlet end, a coal reservoir simulation device, and a gas-liquid separation device. This device separates the gas-water-coal powder multiphase fluid formed by coal powder water and the medium gas into coalbed methane and liquid. A first valve and a second valve are respectively installed at the inlet end and the liquid inlet end. First, second, third, and fourth pressure gauges measure the pressure at the inlet end, the liquid inlet end, the outlet end, and the liquid inlet end, respectively. Coal powder water of different concentrations is prepared, and each preset concentration is added to the coal reservoir simulation device in each experiment. The first and second valves are adjusted to regulate the flow rates at the inlet end and the inlet end, resulting in coal powder water with different saturations. This yields phase permeation curves of coal powder water with different concentrations based on different preset saturations. This allows for the quantitative simulation of coal powder production dynamics in coal reservoirs, the study of gas-water production characteristics within coal reservoir cleavages, and thus guidance for coalbed methane drainage processes.

[0015] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. In the drawings: Figure 1 A schematic diagram of a gas-water-coal pulverized coal multiphase flow experimental apparatus according to an embodiment of this application is shown. Figure 2 A schematic diagram of the flow chart of a gas-water-coal pulverized coal multiphase flow experimental apparatus according to another embodiment of this application is shown. Figure 3 A schematic diagram of a coal reservoir simulation apparatus according to an embodiment of this application is shown. Figure 4 The schematic diagram illustrates a flow chart of a gas-water-coal pulverized coal multiphase flow experimental method according to an embodiment of this application.

[0017] Explanation of reference numerals in the attached figures Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustration and explanation of the embodiments of this application and are not intended to limit the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] Figure 1 A schematic diagram of a gas-water-pulverized coal multiphase flow experimental apparatus according to an embodiment of this application is shown. (Reference) Figure 1 In one embodiment, a gas-water-coal pulverized coal multiphase flow experimental apparatus is provided, comprising: The air inlet 110 is connected to the first end A of the coal reservoir simulation device 120 and is used to inject medium gas into the coal reservoir simulation device. The liquid inlet end 130 is connected to the first end A and is used to inject pulverized coal water into the coal reservoir simulation device 120. The coal reservoir simulation device 120 is used to simulate the dynamic process of coal powder water and medium gas flowing together through the coal reservoir simulation device. A gas-liquid separation device, connected to a coal reservoir simulation device 120, is used to separate the gas-water-coal powder multiphase fluid flowing out of the coal reservoir simulation device 120 into coalbed methane and coal powder-containing liquid. The gas outlet 140 is connected to the second end B of the gas-liquid separator 160, and the coalbed methane flows out from the gas outlet 140. The liquid outlet 150 is connected to the second end B, and the liquid flows out from the liquid outlet 150. The first valve 161 is located between the air inlet end 110 and the first end A, and is used to regulate the gas flow rate of the air inlet end 110. The second valve 162 is located between the liquid inlet end and the first end and is used to regulate the liquid flow rate at the liquid inlet end. The first pressure gauge 171 is installed between the first valve 161 and the first end A, and is used to detect the first pressure of the gas at the inlet end 110; The second pressure gauge 172 is located between the second valve 162 and the first end A, and is used to detect the second pressure of the liquid at the inlet end 150; The third pressure gauge 173 is located between the second end B and the outlet end 140 and is used to detect the third pressure of the gas at the outlet end 140. The fourth pressure gauge 174 is located between the second end B and the outlet end 150 and is used to detect the fourth pressure of the liquid at the outlet end 150.

[0020] Seepage refers to the flow process of gas-liquid two-phase flow in a porous medium (coal seam). To study the seepage law of gas-liquid two-phase flow in coalbed methane reservoirs, the coal reservoir simulation device in the gas-water-coal powder multiphase seepage experimental apparatus of this application simulates the seepage characteristics of coal seam samples, simulating the dynamic process of coal powder water and medium gas flowing together through the coal reservoir simulation device, forming a gas-water-coal powder multiphase fluid. Specifically, medium gas is injected into the coal reservoir simulation device 120 through the gas inlet 110. The medium gas can be pure methane or a methane-based gas that can be adsorbed into the coal seam, or it can be configured with different components such as CH4+N2+CO2, depending on the research purpose. Coal powder water is injected into the coal reservoir simulation device 120 through the liquid inlet 130. Coal powder water refers to a mixture of coal powder and water. The gas-water-coal powder multiphase fluid of medium gas and medium gas flows into the coal reservoir simulation device 120 from end A, and after separation by the gas-liquid separation device 160, flows out from end B. Coalbed methane is discharged from the gas outlet 140, and the separated coal-powder-containing liquid flows out from the liquid outlet 150. The first pressure gauge 171, the second pressure gauge 172, the third pressure gauge 173, and the fourth pressure gauge 174 can record the pressure changes along the flow path of gas and water when simulating the seepage of coal seam samples using the gas-water-coal-powder multiphase seepage experimental device. This allows for the determination of the gas-liquid phase seepage curve of the target coal seam sample, quantitative simulation of coal powder production dynamics in the coal reservoir, and study of gas-water production characteristics within coal reservoir cleavages. Ultimately, this enables the calculation and prediction of gas and water production and recovery rates, guiding the coalbed methane reservoir drainage process.

[0021] refer to Figure 1 In one embodiment, the experimental apparatus further includes: a first flow meter 181, disposed between the first valve 161 and the first end A, for detecting the gas flow rate at the inlet end 110; a second flow meter 182, disposed between the second valve 162 and the first end A, for detecting the liquid flow rate at the liquid inlet end 130; a third flow meter 183, disposed between the outlet end 150 and the second end B, for detecting the liquid flow rate at the outlet end 150; and a fourth flow meter 184, disposed between the outlet end 140 and the second end B, for detecting the gas flow rate at the outlet end 140.

[0022] refer to Figure 1In one embodiment, the experimental apparatus further includes: a third valve 163, located at the first end A, which, when opened, allows pulverized coal water and medium gas to enter the coal reservoir simulation device 120; a fourth valve 164, located at the second end B, which, when opened, allows the gas-water-pulverized coal multiphase fluid to flow out of the coal reservoir simulation device; a fifth valve 165, located at the gas outlet 140, which, when opened, allows coalbed methane to flow out of the gas outlet 140; and a sixth valve 166, located at the liquid outlet 150, which, when opened, allows liquid to flow out of the liquid outlet 150. By setting up the above multiple valves, the flow of gas and liquid along the process can be controlled at any time, facilitating research and teaching demonstrations by experimental personnel.

[0023] refer to Figure 2 In one embodiment, the experimental apparatus further includes: a gas supply device 210, located at the gas inlet, for supplying gas to the coal reservoir simulation device; a stirring device 220, located at the liquid inlet 130, for stirring coal powder water; a gas collection device 230, located at the gas outlet 140, for collecting coalbed methane discharged from the gas-liquid separator 160; and a liquid collection device 240, located at the liquid outlet 150, for collecting liquid discharged from the gas-liquid separator 160. The gas supply device can be a gas cylinder, the liquid collection device can be a return water tank, and the gas collection device can be a gas collection cylinder. The gas cylinder can inject medium gas at a set pressure, causing the medium gas to fill and adsorb into the fractures and pores of the coal seam sample in the coal reservoir simulation device.

[0024] refer to Figure 3 In one implementation, the coal reservoir simulation device 120 can be filled with rectangular transparent blocks of different sizes, with gaps between these blocks to simulate the cleavage and fractures in the coal reservoir. Then, a top plate is placed over the coal reservoir simulation device 120. During the experiment, the seepage process of coalbed methane from the coal reservoir simulation device can be observed visually, simulating the formation of a gas-water-coal-powder multiphase fluid by the co-flow of pulverized coal, water, and gaseous media through the coal reservoir, thus achieving visualized observation of the gas-water-coal-powder multiphase seepage process in the coal reservoir.

[0025] Figure 4 A schematic flowchart of a gas-water-pulverized coal multiphase flow experimental method according to an embodiment of this application is shown. (Reference) Figure 4 A method for multiphase flow experiment of gas-water-pulverized coal is provided, which is applied to a multiphase flow experiment device of gas-water-pulverized coal. The method includes: S402, configured with multiple preset concentrations of pulverized coal water, and sequentially adding each preset concentration of pulverized coal water to the coal reservoir simulation device through the inlet end.

[0026] S404, for each preset concentration of pulverized coal water, adjust the first valve and the second valve so that the saturation of the preset concentration of pulverized coal water reaches the preset saturation level.

[0027] S406, for each preset concentration of pulverized coal water, determine the relative permeability of the water phase and the relative permeability of the gas phase at each preset saturation level.

[0028] S408, for each preset concentration of pulverized coal water, determine the relative permeability curve of pulverized coal water at the preset concentration based on different preset saturations according to multiple gas phase relative permeability and water phase relative permeability of pulverized coal water at the preset concentration.

[0029] Specifically, coal powder of standard mesh size is ground and screened, and multiple coal powder water solutions with different preset concentrations are prepared. Starting from the lowest concentration, the prepared coal powder water solutions of preset concentrations are added to the air inlet 110 during each test, and the coal powder water is stirred to ensure uniform mixing. The first valve 161 and the second valve 162 are adjusted to control the flow rate of the medium gas and coal powder water entering the coal reservoir simulation device 120 through the air inlet 110 and the liquid inlet 130, so that the saturation of the coal powder water solution of preset concentration reaches the preset saturation level.

[0030] Because the pore structure of coal and its role in reservoirs differ from those of conventional reservoirs, the representation of the relative permeability curve of coal-rock gas-water also has its unique characteristics. Water in the micropores of bedrock is bound water; its water saturation level does not affect seepage. The relative permeability of coal-rock gas and water is the relative permeability of the gas and water phases within the cleavage. The absolute permeability curve should reflect the flow characteristics of gas and water within the cleavage; that is, the saturation reflecting the change in relative permeability is not the total water saturation within the sample, but rather the water saturation within the cleavage. The unique characteristics of the pore structure and its role determine that the effect of relative permeability of coal-rock gas and water also differs from that of conventional natural gas reservoirs. In conventional natural gas reservoirs, the initial producing phase is the gas phase, and gas-water two-phase flow only appears towards the end of gas production. At this point, relative permeability data of gas and water are needed to study the flow characteristics of the gas and water phases as saturation changes and to calculate gas recovery. However, the initial producing phase of coalbed methane reservoirs is the water phase. Therefore, gas and water relative permeability data are needed for coalbed methane reservoirs to study the gas and water production characteristics within coal reservoir cleavages, and to calculate and predict gas and water production and recovery rates. Thus, when the saturation of pulverized coal water reaches a preset saturation level, the pressure readings of the first pressure gauge 171, the second pressure gauge 172, the third pressure gauge 173, and the fourth pressure gauge 174 are read to determine the relative permeability of the water phase and the relative permeability of the gas phase at each preset saturation level. Based on the multiple relative permeability of the gas phase and the relative permeability of the water phase at each preset concentration of pulverized coal water, the relative permeability curves of pulverized coal water at each preset concentration based on different preset saturation levels can be determined.

[0031] In one embodiment, determining the relative permeability of the aqueous phase and the relative permeability of the gas phase at each preset saturation level for each preset concentration of pulverized coal water includes: for each preset concentration of pulverized coal water, with the liquid flow rate at the inlet end being the same as the liquid flow rate at the outlet end, and the gas flow rate at the inlet end being the same as the gas flow rate at the outlet end, obtaining the first pressure at the inlet end, the second pressure at the inlet end, the third pressure at the outlet end, and the fourth pressure at the outlet end of the pulverized coal water at each preset saturation level using a first pressure gauge, a second pressure gauge, a third pressure gauge, and a fourth pressure gauge, respectively; and determining the relative permeability of the aqueous phase and the relative permeability of the gas phase at each preset saturation level for each preset concentration of pulverized coal water based on the first pressure, the second pressure, the third pressure, and the fourth pressure.

[0032] The flow rates of the medium gas and pulverized coal water entering the coal reservoir simulation device 120 through the air inlet 110 and liquid inlet 130 are controlled by adjusting the first valve 161 and the second valve 162, so that the saturation of the pulverized coal water at the preset concentration reaches the preset saturation level. For each preset concentration of pulverized coal water, multiple multiphase flow tests with different preset saturation levels can be performed. The liquid flow rates at the liquid inlet and liquid outlet, as well as the gas flow rates at the air inlet and air outlet, can be determined by the readings of the first flow meter 181, the second flow meter 182, the third flow meter 183, and the fourth flow meter 184. When the flow rates of the first flow meter 181 and the fourth flow meter 184 are the same and remain stable, and the flow rates of the second flow meter 182 and the third flow meter 183 are the same and remain stable, it indicates that the liquid flow rate at the liquid inlet is the same as the liquid flow rate at the liquid outlet, and the gas flow rate at the air inlet is the same as the gas flow rate at the air outlet. At this point, the pressure at the inlet of the pulverized coal water, the second pressure at the inlet, the third pressure at the outlet, and the fourth pressure at the outlet can be obtained using the aforementioned pressure gauge at each preset saturation level. Then, for each preset concentration of pulverized coal water, the relative permeability of the aqueous phase and the relative permeability of the gas phase at each preset saturation level are determined based on the first, second, third, and fourth pressures.

[0033] In one embodiment, determining the relative permeability of the aqueous phase and the relative permeability of the gas phase of pulverized coal water at each preset saturation level based on a first pressure, a second pressure, a third pressure, and a fourth pressure includes: determining the effective permeability of the aqueous phase of pulverized coal water at each preset saturation level based on the second pressure and the fourth pressure; determining the effective permeability of the gas phase of pulverized coal water at each preset saturation level based on the first pressure and the third pressure; determining the absolute permeability of pulverized coal water at each preset concentration; and determining the relative permeability of the aqueous phase of pulverized coal water at each preset saturation level based on the ratio between the effective permeability of the aqueous phase and the absolute permeability, and determining the relative permeability of the gas phase of pulverized coal water at each preset saturation level based on the ratio between the effective permeability of the gas phase and the absolute permeability.

[0034] For each preset concentration of pulverized coal water, based on Darcy's law, the effective gas-phase permeability of pulverized coal water at each preset saturation level can be determined using the first and third pressures, and the effective aqueous-phase permeability of pulverized coal water at each preset saturation level can be determined using the second and fourth pressures. To determine the absolute permeability of pulverized coal water at each preset concentration, the readings of the second and fourth pressure gauges must be obtained when the saturation level of the pulverized coal water at that preset concentration is 1 (i.e., no gas is introduced into the coal reservoir simulation device). Based on Darcy's law, the absolute permeability of pulverized coal water can be determined using the second and fourth pressures. Furthermore, the relative aqueous-phase permeability of pulverized coal water at each preset saturation level is determined based on the ratio between the effective aqueous-phase permeability and the absolute permeability, and the relative gas-phase permeability of pulverized coal water at each preset saturation level is determined based on the ratio between the effective gas-phase permeability and the absolute permeability.

[0035] In one embodiment, for each preset concentration of pulverized coal water, determining the effective permeability of the aqueous phase at each preset saturation level based on the second pressure and the fourth pressure includes calculating the effective permeability of the aqueous phase according to the following formula (1): (1) in, This refers to the effective permeability of the aqueous phase in pulverized coal water. This refers to the preset saturation level of the pulverized coal water. This refers to the viscosity of the coal powder water. This refers to the length of the coal reservoir simulation device. This refers to the flow rate of liquid entering the coal reservoir simulation device at the inlet end. This refers to the cross-sectional area of ​​the coal reservoir simulation device. It refers to the pressure difference between the fourth pressure and the second pressure.

[0036] In one embodiment, determining the effective gas-phase permeability of pulverized coal water at each preset saturation level based on a first pressure and a third pressure for each preset concentration of pulverized coal water includes: determining the gas viscosity and deviation coefficient of the experimental device based on the arithmetic mean of the first pressure and the third pressure for each preset concentration of pulverized coal water; obtaining the device parameters of the coal reservoir simulation device, including the device cross-sectional area and device length; and determining the effective gas-phase permeability of pulverized coal water at each preset saturation level for each preset concentration of pulverized coal water based on the device parameters, gas viscosity, deviation coefficient, first pressure, and third pressure.

[0037] The viscosity of coalbed methane can be calculated using the Lee-Gonzalez semi-empirical correlation method at different pressures.

[0038] In one embodiment, for each preset concentration of pulverized coal water, determining the relative permeability of the gas phase at each preset saturation level based on device parameters, gas viscosity, deviation coefficient, first pressure, and third pressure includes calculating the relative permeability of the gas phase according to the following formula (2): (2) in, This refers to the effective gas-phase permeability of pulverized coal water. This refers to the preset saturation level of the pulverized coal water. This refers to standard atmospheric pressure. This refers to the gas flow rate entering the coal reservoir simulation device at the inlet end. This refers to the gas viscosity of coalbed methane under average pressure in a coal reservoir simulation device. This refers to the length of the coal reservoir simulation device. This refers to the cross-sectional area of ​​the coal reservoir simulation device. The deviation coefficient of coalbed methane in a coal reservoir simulation device under average pressure, where average pressure refers to the arithmetic mean of the first and third pressures. This refers to the first pressure. It refers to the third pressure.

[0039] In one embodiment, determining the absolute permeability of pulverized coal water for each preset concentration includes calculating the absolute permeability according to the following formula (3): (3) in, This refers to the absolute permeability of pulverized coal water. This refers to the saturation of pulverized coal water. This refers to the viscosity of the coal powder water. This refers to the length of the coal reservoir simulation device. This refers to the flow rate of liquid entering the coal reservoir simulation device at the inlet end. This refers to the cross-sectional area of ​​the coal reservoir simulation device. It refers to the pressure difference between the fourth pressure and the second pressure.

[0040] In one specific embodiment, a multiphase flow test method for gas-water-pulverized coal is provided, including the following steps: S1. Fill the coal reservoir simulation device 120 with rectangular transparent blocks of different sizes, and then cover it with the top plate of the coal reservoir simulation device 120.

[0041] S2. Grind and screen coal powder to obtain standard mesh size, and prepare multiple coal powder water solutions with different preset concentrations. Starting from the lowest concentration, add the prepared coal powder water solution of the preset concentration to the stirring device 220 in each test, and stir the coal powder water solution to make the coal powder water solution uniformly mixed.

[0042] S3. Open the second valve 162, the third valve 163, the fourth valve 164, and the sixth valve 166. Adjust the second valve 162 so that the readings of the second flow meter 182 and the third flow meter 183 are both stable at 10cm. 3 Stop twisting after 1 / min (when the pulverized coal water saturation is 1). At this time, read the readings of the second pressure gauge 172 and the fourth pressure gauge 174. Then, calculate the absolute permeability of the pulverized coal water at the preset concentration according to the following formula (3): (3) in, This refers to the absolute permeability of pulverized coal water. This refers to the saturation of pulverized coal water. This refers to the viscosity of the coal powder water. This refers to the length of the coal reservoir simulation device. This refers to the flow rate of liquid entering the coal reservoir simulation device at the inlet end. This refers to the cross-sectional area of ​​the coal reservoir simulation device. It refers to the pressure difference between the fourth pressure and the second pressure.

[0043] S4. Next, open the first valve 161 and the fifth valve 165, and adjust the first valve 161 and the second valve 162 so that the readings of the second flow meter 182 and the third flow meter 183 are both stable at 9cm. 3 / min, and the readings of the first flow meter 181 and the fourth flow meter 184 are stable at 1cm. 3 Stop twisting after 0.9 min (i.e., 0.9 for coal powder water saturation and 0.1 for gas saturation). At this time, read the readings of the first pressure gauge 171, the second pressure gauge 172, the third pressure gauge 173, and the fourth pressure gauge 174. Then, calculate the effective permeability of the aqueous phase according to the following formula (1): (1) in, This refers to the effective permeability of the aqueous phase in pulverized coal water. This refers to the preset saturation level of the pulverized coal water. This refers to the viscosity of the coal powder water. This refers to the length of the coal reservoir simulation device. This refers to the flow rate of liquid entering the coal reservoir simulation device at the inlet end. This refers to the cross-sectional area of ​​the coal reservoir simulation device. It refers to the pressure difference between the fourth pressure and the second pressure.

[0044] The relative permeability of the gas phase is calculated according to the following formula (2): (2) in, This refers to the effective gas-phase permeability of pulverized coal water. This refers to the preset saturation level of the pulverized coal water. This refers to standard atmospheric pressure. This refers to the gas flow rate entering the coal reservoir simulation device at the inlet end. This refers to the gas viscosity of coalbed methane under average pressure in a coal reservoir simulation device. This refers to the length of the coal reservoir simulation device. This refers to the cross-sectional area of ​​the coal reservoir simulation device. The deviation coefficient of coalbed methane in a coal reservoir simulation device under average pressure, where average pressure refers to the arithmetic mean of the first and third pressures. This refers to the first pressure. This refers to the third pressure. The gas viscosity of coalbed methane is calculated using the Lee-Gonzalez semi-empirical correlation method.

[0045] S5. Calculate the relative permeability of the aqueous phase at different preset concentrations of pulverized coal with a water saturation of 0.9 and a gas saturation of 0.1. and gas phase relative permeability value .

[0046] S6. Repeat steps S2-S5 above, adjusting the first valve 161 and the second valve 162, and test the relative permeability values ​​at different preset concentrations of pulverized coal water saturation of 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.1. and .

[0047] S7. Obtain the phase permeability curves of pulverized coal water at each preset concentration based on the above-mentioned different preset saturations.

[0048] Multiphase flow experiments using the aforementioned gas-water-coal powder multiphase flow experimental apparatus were conducted. The flow rates of coal powder and medium gas entering the coal reservoir simulation device were adjusted via valves. Readings from multiple flow meters and pressure gauges were recorded to calculate the relative permeability of the gas phase and water phase at different preset concentrations of coal powder water under different saturations. This generated relative permeability curves of coal powder water at different preset concentrations based on different preset saturations. This achieved the visualization and reconstruction of the dual media characteristics of the coal reservoir matrix and cleavage, as well as the function of constant coal powder concentration flow. Combined with the experimental method of relative permeability testing, it is possible to observe the seepage characteristics of coal reservoirs under different coal powder concentrations and test relative permeability curves, calculating and predicting gas and water production and recovery rates.

[0049] Figure 4 This is a schematic flowchart of a gas-water-pulverized coal multiphase flow experimental method in one embodiment. It should be understood that, although... Figure 4 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise explicitly stated herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 4 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0050] It should also be noted that 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. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0051] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A gas-water-coal-powder multiphase percolation experiment method, characterized in that, The experimental method is applied to a gas-water-coal powder multiphase flow experimental device. The experimental device includes: an inlet end, connected to a first end of a coal reservoir simulation device, for injecting medium gas into the coal reservoir simulation device; a liquid inlet end, connected to the first end, for injecting coal powder water into the coal reservoir simulation device; the coal reservoir simulation device is filled with rectangular transparent blocks of different sizes, with gaps between the rectangular transparent blocks to simulate coal reservoir cleavage and fractures; the coal reservoir simulation device is equipped with a top plate to seal the rectangular transparent blocks, used to simulate the dynamic process of the coal powder water and the medium gas flowing together through the coal reservoir simulation device; a gas-liquid separation device, connected to the coal reservoir simulation device, for separating the gas-water-coal powder multiphase fluid flowing from the coal reservoir simulation device into coalbed methane and coal powder-containing liquid; and an outlet end, connected to a second end of the gas-liquid separation device. The coalbed methane flows out from the gas outlet; the liquid outlet is connected to the second end, and the liquid flows out from the liquid outlet; a first valve is disposed between the gas inlet and the first end for adjusting the gas flow rate at the gas inlet; a second valve is disposed between the liquid inlet and the first end for adjusting the liquid flow rate at the liquid inlet; a first pressure gauge is disposed between the first valve and the first end for detecting the first pressure of the gas at the gas inlet; a second pressure gauge is disposed between the second valve and the first end for detecting the second pressure of the liquid at the liquid inlet; a third pressure gauge is disposed between the second end and the gas outlet for detecting the third pressure of the gas at the gas outlet; a fourth pressure gauge is disposed between the second end and the liquid outlet for detecting the fourth pressure of the liquid at the liquid outlet; the experimental method includes: Multiple preset concentrations of pulverized coal water are prepared, and each preset concentration of pulverized coal water is added to the coal reservoir simulation device through the inlet end in sequence. For each preset concentration of pulverized coal water, adjust the first valve and the second valve to make the saturation of the preset concentration of pulverized coal water reach the preset saturation level. For each preset concentration of pulverized coal water, under saturated conditions in the coal reservoir simulation device where only the pulverized coal water is injected and no medium gas is injected, the absolute permeability of the preset concentration of pulverized coal water is determined based on the readings of the second and fourth pressure gauges. For each preset concentration of pulverized coal water, determine the relative permeability of the water phase and the relative permeability of the gas phase at each preset saturation level; For each preset concentration of pulverized coal water, a relative permeability curve of pulverized coal water at the preset concentration based on different preset saturations is determined according to multiple gas phase relative permeability and water phase relative permeability of the preset concentration of pulverized coal water.

2. The experimental method for multiphase flow of gas-water-pulverized coal according to claim 1, characterized in that, The experimental setup also includes: A first flow meter is installed between the first valve and the first end to detect the gas flow rate at the inlet end. A second flow meter is installed between the second valve and the first end to detect the liquid flow rate at the inlet end; A third flow meter is provided between the liquid outlet and the second end for detecting the liquid flow rate at the liquid outlet. A fourth flow meter is provided between the outlet end and the second end for detecting the gas flow rate at the outlet end.

3. The experimental method for multiphase flow of gas-water-pulverized coal according to claim 1, characterized in that, The experimental setup also includes: A gas supply device, located at the gas inlet, is used to supply gas to the coal reservoir simulation device; A stirring device is provided at the liquid inlet end for stirring the pulverized coal water; A gas collection device is installed at the gas outlet end to collect coalbed methane discharged from the gas-liquid separator. A liquid collection device is provided at the liquid outlet end for collecting the liquid discharged from the gas-liquid separator.

4. The experimental method for multiphase flow of gas-water-pulverized coal according to claim 1, characterized in that, The experimental setup also includes: A third valve is provided at the first end. When the third valve is opened, the pulverized coal water and the medium gas enter the coal reservoir simulation device. A fourth valve is located at the second end. When the fourth valve is opened, the gas-water-coal powder multiphase fluid flows out from the coal reservoir simulation device. The fifth valve is located at the gas outlet end. When the fifth valve is opened, the coalbed methane flows out from the gas outlet end. A sixth valve is provided at the liquid outlet end, and when the sixth valve is opened, the liquid flows out from the liquid outlet end.

5. The experimental method for multiphase flow of gas-water-pulverized coal according to claim 1, characterized in that, The determination of the relative permeability of the aqueous phase and the relative permeability of the gas phase of the pulverized coal water at each preset saturation level for each preset concentration includes: For each preset concentration of pulverized coal water, when the liquid flow rate at the inlet end is the same as the liquid flow rate at the outlet end, and the gas flow rate at the inlet end is the same as the gas flow rate at the outlet end, the first pressure at the inlet end, the second pressure at the inlet end, the third pressure at the outlet end, and the fourth pressure at the outlet end are obtained by the first pressure gauge, the second pressure gauge, the third pressure gauge, and the fourth pressure gauge, respectively, at each preset saturation level. For each preset concentration of pulverized coal water, the relative permeability of the water phase and the relative permeability of the gas phase at each preset saturation level are determined based on the first pressure, the second pressure, the third pressure, and the fourth pressure.

6. The experimental method for multiphase flow of gas-water-pulverized coal according to claim 5, characterized in that, For each preset concentration of pulverized coal water, the relative permeability of the aqueous phase and the relative permeability of the gas phase at each preset saturation level are determined based on the first pressure, the second pressure, the third pressure, and the fourth pressure, including: For each preset concentration of pulverized coal water, the effective permeability of the aqueous phase of the pulverized coal water at each preset saturation level is determined based on the second pressure and the fourth pressure. For each preset concentration of pulverized coal water, the effective gas phase permeability of the pulverized coal water at each preset saturation level is determined based on the first pressure and the third pressure. For each preset concentration of pulverized coal water, the relative permeability of the aqueous phase at each preset saturation level is determined based on the ratio between the effective permeability of the aqueous phase and the absolute permeability, and the relative permeability of the gas phase at each preset saturation level is determined based on the ratio between the effective permeability of the gas phase and the absolute permeability.

7. The experimental method for multiphase flow of gas-water-pulverized coal according to claim 6, characterized in that, For each preset concentration of pulverized coal water, the effective permeability of the aqueous phase at each preset saturation level is determined based on the second pressure and the fourth pressure, including calculating the effective permeability of the aqueous phase according to the following formula (1): （1） in, This refers to the effective permeability of the aqueous phase in the pulverized coal water. This refers to the preset saturation level of the pulverized coal water. This refers to the viscosity of the pulverized coal water. This refers to the length of the coal reservoir simulation device. This refers to the liquid flow rate entering the coal reservoir simulation device from the inlet end. This refers to the cross-sectional area of ​​the coal reservoir simulation device. This refers to the pressure difference between the fourth pressure and the second pressure.

8. The experimental method for multiphase flow of gas-water-pulverized coal according to claim 6, characterized in that, The determination of the effective gas-phase permeability of the pulverized coal water at each preset saturation level, based on the first pressure and the third pressure, for each preset concentration, includes: For each preset concentration of pulverized coal water, the gas viscosity and deviation coefficient of the experimental device are determined based on the arithmetic mean of the first pressure and the third pressure. Obtain the device parameters of the coal reservoir simulation device, the device parameters including the device cross-sectional area and device length; For each preset concentration of pulverized coal water, the effective gas phase permeability of the pulverized coal water at each preset saturation level is determined based on the device parameters, the gas viscosity, the deviation coefficient, the first pressure, and the third pressure.

9. The experimental method for multiphase flow of gas-water-pulverized coal according to claim 8, characterized in that, The determination of the relative permeability of the coal powder water at each preset saturation level for each preset concentration, based on the device parameters, the gas viscosity, the deviation coefficient, the first pressure, and the third pressure, includes calculating the relative permeability of the gas phase according to the following formula (2): （2） in, This refers to the effective gas-phase permeability of the pulverized coal water. This refers to the preset saturation level of the pulverized coal water. This refers to standard atmospheric pressure. This refers to the gas flow rate entering the coal reservoir simulation device at the inlet end. This refers to the gas viscosity of coalbed methane under average pressure in the coal reservoir simulation device. This refers to the length of the coal reservoir simulation device. This refers to the cross-sectional area of ​​the coal reservoir simulation device. The deviation coefficient of coalbed methane in the coal reservoir simulation device under average pressure, where the average pressure refers to the arithmetic mean of the first pressure and the third pressure. This refers to the first pressure. This refers to the third pressure.

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