A system, method for simulating hydrate depressurization production

Abstract

This invention discloses a system for simulating hydrate depressurization extraction, comprising a pipeline, a constant temperature module, a backpressure module, a metering module, and a data acquisition module. The invention also discloses a method for simulating hydrate depressurization extraction, comprising the following steps: S5, adjusting the temperature of the pipeline using the constant temperature module; S6, adjusting the pressure at the outlet end of the pipeline using the backpressure module, so that the pressure at the outlet end of the pipeline is less than the pressure at the inlet end of the pipeline; S7, injecting hydrate into the inlet end of the pipeline; S8, detecting the temperature and pressure at various points inside the pipeline, and simultaneously metering the gas flow rate output by the backpressure module. This application conducts experiments using the above system and method. The system uses data collected by the data acquisition module and metering module to determine whether the decomposed hydrate forms secondary hydrate or ice inside the porous medium, thereby drawing conclusions about the impact of gas throttling expansion on hydrates.

Description

Technical Field

[0001] This invention relates to the field of physical analysis of porous media, specifically to a system for simulating depressurization mining of hydrates. This invention also relates to a method for simulating depressurization mining of hydrates. Background Technology

[0002] In the production process of extracting methane gas by breaking the phase equilibrium boundary of natural gas hydrate using the depressurization method, the hydrate continuously absorbs heat from the surrounding strata and decomposes into gas and water that are extracted. As the hydrate decomposition front continues to diffuse towards the ore body boundary, the area of ​​reduced formation temperature expands due to the endothermic effect of hydrate decomposition. At the same time, the temperature drop is more pronounced in the hydrate decomposition zone around the production well due to the gas throttling and expansion. Under certain temperature and pressure conditions, secondary hydrates or ice may form, causing blockage of the effective seepage channels in the reservoir in this area, increasing seepage resistance, and affecting the production of hydrate decomposition gas.

[0003] Therefore, an experimental system is needed to simulate the process of gas produced by hydrate decomposition seeping from the decomposition front to the production wellbore, observe the seepage behavior of ice and hydrate secondary formation evolution under different production pressure differentials, and explore the main controlling factors and formation mechanisms of ice and secondary hydrate formation in the decomposition zone by monitoring the changes of multiple parameters such as reservoir temperature, pressure, and saturation during the experimental process. Summary of the Invention

[0004] The purpose of this invention is to provide a system for simulating depressurized mining of hydrates, thereby filling the technical gap in existing experimental systems that cannot simulate the process of gas produced by hydrate decomposition seeping from the decomposition front to the production wellbore.

[0005] To solve the above technical problems:

[0006] This application provides a system for simulating hydrate depressurization extraction, including a pipeline, a constant temperature module, a back pressure module, a metering module, and a data acquisition module; the pipeline has an inlet end and an outlet end, and the inside of the pipeline is filled with a porous medium; the constant temperature module is used to maintain a constant temperature in the pipeline; the input end of the back pressure module is connected to the outlet end of the pipeline; the metering module is used to measure the gas flow rate output by the back pressure module; and the data acquisition module is used to collect the pressure at the inlet and outlet ends of the pipeline, as well as the temperature and pressure of various parts inside the pipeline.

[0007] Preferably, the system further includes a gas-liquid separator, the input end of which is connected to the output end of the back pressure module, and the metering module is located at the gas outlet end of the gas-liquid separator.

[0008] Preferably, the system further includes a gas source and a liquid source, both of which are connected to the inlet end of the pipeline.

[0009] Preferably, the gas source includes a gas storage cylinder and a first constant speed and constant pressure module. The first constant speed and constant pressure module includes a gas booster pump, a high-pressure storage tank, a pressure regulating valve, and a flow controller. The output end of the gas storage cylinder is connected to the input end of the high-pressure storage tank through the gas booster pump. The output end of the high-pressure storage tank is connected to the inlet end of the pipeline in sequence through the pressure regulating valve and the flow controller.

[0010] Preferably, the pipeline includes multiple pipes that are sequentially connected to each other, and the pipes are detachably connected to each other.

[0011] Preferably, the thermostatic module includes a combined bath and a refrigeration module, with the piping installed inside the thermostatic module.

[0012] Preferably, the outside of the pipe is wrapped with thermal insulation material.

[0013] This application also provides a method for simulating hydrate depressurization mining, the method using the system described above, the method comprising the following steps: S5, adjusting the temperature of the pipeline using a constant temperature module; S6, adjusting the pressure at the outlet end of the pipeline using a back pressure module, so that the pressure at the outlet end of the pipeline is less than the pressure at the inlet end of the pipeline; S7, injecting hydrate into the inlet end of the pipeline; S8, detecting the temperature and pressure at various parts inside the pipeline, and simultaneously measuring the gas flow rate output by the back pressure module.

[0014] Preferably, the system further includes a gas source and a liquid source, and the method further includes the following steps: S2, measuring the porosity of the porous medium: evacuating the inside of the pipeline, using the liquid source to input liquid into the inlet end of the pipeline, and recording the volume of the input liquid when the pressure inside the pipeline increases to a preset value; S3, measuring the permeability of the porous medium: using the liquid source to input liquid into the inlet end of the pipeline at a constant flow; S4, calculating the initial water saturation of the porous medium: using the gas source to inject gas into the inlet end of the pipeline until no more water is output from the outlet end of the pipeline, and recording the volume of water displaced.

[0015] Preferably, the method further includes the following steps: S1, testing the airtightness of the pipeline: sealing the outlet end of the pipeline, using a gas source to input gas into the inlet end of the pipeline and maintaining pressure.

[0016] Compared with the prior art, this application has the following advantages:

[0017] This application uses the above-described structure to construct an experimental system. During gas permeation, the secondary hydrates and ice formed in the porous medium directly affect the gas pressure and temperature inside the pipeline, and also affect the gas production rate at the output of the back pressure module. The system collects the temperature and pressure at the inlet and outlet of the pipeline, as well as at various parts inside the pipeline, and combines this with the gas flow rate collected by the metering module to determine whether the decomposed hydrates have formed secondary hydrates or ice inside the porous medium, thereby drawing conclusions about the impact of gas throttling expansion on hydrates. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0019] Figure 1 This is a system diagram provided for an embodiment of the present invention.

[0020] Figure 2 This is a flowchart of a method provided in an embodiment of the present invention.

[0021] The labels in the diagram represent the following:

[0022] 1-Gas cylinder;

[0023] 2-First constant speed and constant pressure module; 2a-Gas booster pump; 2b-High pressure storage tank; 2c-Pressure regulating valve; 2d-Flow controller;

[0024] 3-Second constant speed and constant pressure module;

[0025] 4-Pipelines;

[0026] 5-Thermostatic module;

[0027] 6-Back pressure module;

[0028] 7-Gas-liquid separator;

[0029] 8-Metering module; 8a-Gas flow meter; 8b-Container; 8c-Electronic balance;

[0030] T - Temperature sensor; P - Pressure sensor. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] For example Figure 1 As shown, this application provides:

[0033] A system for simulating hydrate depressurization extraction includes a pipeline 4, a constant temperature module 5, a back pressure module 6, a metering module 8, and a data acquisition module. The pipeline 4 has an inlet end and an outlet end, and the interior of the pipeline 4 is filled with a porous medium. The constant temperature module 5 is used to maintain a constant temperature in the pipeline 4. The input end of the back pressure module 6 is connected to the outlet end of the pipeline 4. The metering module 8 is used to meter the gas flow rate output by the back pressure module 6. The data acquisition module is used to collect the pressure at the inlet and outlet ends of the pipeline 4, as well as the temperature and pressure of various parts inside the pipeline 4.

[0034] Based on the above embodiments, the technical problem this application aims to solve is how to experiment with the effect of gas throttling expansion on hydrates. To this end, this application uses the above-described structure to construct a system for the experiment. At the start of the experiment, hydrates are introduced into the inlet of pipeline 4. The temperature control module 5 is manipulated to maintain the temperature of pipeline 4 at the reservoir temperature of the natural gas hydrate decomposition zone. The backpressure module 6 is manipulated to maintain a certain pressure at the outlet of pipeline 4, which is lower than the pressure at the inlet of pipeline 4. Under the pressure difference between the inlet and outlet of pipeline 4, the gas continuously seeps within the porous medium filled inside pipeline 4, thereby simulating the gas seepage process during hydrate depressurization extraction.

[0035] Preferably, the data acquisition module includes a temperature sensor T and a pressure sensor P, with one temperature sensor T and one pressure sensor P placed at 0.25m intervals along the pipeline 4.

[0036] During gas permeation, the pressure gradually decreases, and the volume expands, resulting in continuous throttling expansion. When the temperature drops to the equilibrium temperature, secondary hydrates form in the decomposition zone. If the temperature drops to the freezing point, ice forms. The secondary hydrates and ice formed in the porous medium directly affect the gas pressure and temperature inside pipe 4, and also affect the gas production rate at the output of gas-liquid separator 7. The system collects the temperature and pressure at the inlet and outlet of pipe 4, as well as at various parts inside pipe 4, and combines this with the gas and liquid output collected by metering module 8 to determine whether secondary hydrates or ice form inside the porous medium, thus drawing conclusions about the impact of gas throttling expansion on hydrates.

[0037] It should also be noted that, during the experiment, it was found that the water output of pipe 4 was very small and could be ignored. The experimenters could estimate the hydrate content and saturation based on the difference in gas flow between the inlet and outlet after the pressure difference was established. Therefore, this system does not need to measure the liquid flow rate output by pipe 4.

[0038] The system also includes a gas-liquid separator 7, the input end of which is connected to the output end of the back pressure module 6, and a metering module 8 is installed at the gas outlet end of the gas-liquid separator 7.

[0039] Based on the above embodiments, the technical problem this application aims to solve is how to further improve the experimental accuracy of the system. Although the water output of pipe 4 is very small and can be ignored, this water output still affects the accuracy of the experimental data. To this end, this application sets a gas-liquid separator 7 at the output end of the back pressure module 6 to separate the gas-water mixture output by the back pressure module 6 into gas and liquid. Measuring only the gas flow rate can improve the accuracy of the experimental data.

[0040] Further:

[0041] The system also includes a gas source and a liquid source, both of which are connected to the inlet end of pipeline 4.

[0042] Based on the above embodiments, the technical problem this application aims to solve is how to input hydrate into the inlet of pipeline 4. To this end, this application uses a gas storage cylinder 1 and a first constant speed and pressure module 2 to form a gas source, and a liquid storage bottle (not shown in the figure) and a second constant speed and pressure module 3 to form a liquid source. The gas storage cylinder 1 stores methane with a purity of 99.9%, and the liquid storage bottle stores saline solution with a concentration of 3.5%. The gas storage cylinder 1 and the liquid storage bottle respectively inject methane and saline solution into the inlet of pipeline 4 through the first constant speed and pressure module 2 and the second constant speed and pressure module 3 to form hydrate.

[0043] Further:

[0044] The gas source includes a gas storage cylinder 1 and a first constant speed and constant pressure module 2. The first constant speed and constant pressure module 2 includes a gas booster pump 2a, a high-pressure storage tank 2b, a pressure regulating valve 2c, and a flow controller 2d. The output end of the gas storage cylinder 1 is connected to the input end of the high-pressure storage tank 2b through the gas booster pump 2a. The output end of the high-pressure storage tank 2b is connected to the inlet end of the pipeline 4 through the pressure regulating valve 2c and the flow controller 2d in sequence.

[0045] Based on the above embodiments, the technical problem this application aims to solve is how to ensure that the gas stored inside the gas cylinder 1 is input to the inlet of the pipeline 4 at a constant speed and pressure. To this end, this application uses a gas booster pump 2a to pressurize the gas output from the gas cylinder 1, storing it in a high-pressure storage tank 2b. The high-pressure storage tank 2b then outputs high-pressure gas at a constant pressure through a pressure regulating valve 2c. Simultaneously, the first constant speed and pressure module 2 also regulates the gas flow rate through a flow controller 2d, ensuring that the gas velocity input to the inlet of the pipeline 4 is constant.

[0046] It should also be noted that the data acquisition module also collects the pressure inside the gas cylinder 1, inside the high-pressure storage tank 2b, and at the output end of the pressure regulating valve 2c, thereby ensuring that the gas pressure input to pipeline 4 meets the experimental requirements.

[0047] Preferably, the second constant speed and constant pressure module 3 is a constant speed and constant pressure injection pump.

[0048] Further:

[0049] Pipeline 4 includes multiple pipes that are sequentially connected to each other, and the pipes are detachably connected to each other.

[0050] Based on the above embodiments, the technical problem this application aims to solve is how to simulate the effects of different reservoir depths on secondary hydrates and ice. To this end, this application uses several pipes connected in series to form a pipeline 4, with flanges connecting the pipes. This allows the length of pipeline 4 to be adjusted, enabling the system to simulate different reservoir depths.

[0051] Further:

[0052] The thermostat module 5 includes a combined bath and a refrigeration module, and the pipes 4 are installed inside the thermostat module 5.

[0053] Based on the above embodiments, the technical problem this application aims to solve is how to simulate the temperature of the natural gas hydrate decomposition zone reservoir for pipeline 4. To this end, this application installs pipeline 4 in a combined bath and supplies a low-temperature fluid, such as cold water, to the interior of the combined bath through a refrigeration module, thereby making the temperature of pipeline 4 equal to the temperature of the natural gas hydrate decomposition zone reservoir.

[0054] It should also be noted that a modular bathtub means that the bathtub can be assembled from multiple modules, just like pipe 4. Therefore, the length of the modular bathtub can be increased or decreased with the length of pipe 4.

[0055] Further:

[0056] Pipe 4 is wrapped with insulation material on the outside.

[0057] Based on the above embodiments, the technical problem this application aims to solve is how to reduce the influence of ambient temperature on experiments and prevent the cooling effect caused by the throttling expansion effect of the gas from being offset by the ambient temperature, thus causing unreliable experimental data. To this end, this application uses a stainless steel pipe to fabricate the pipeline 4, and simultaneously wraps an insulation layer around the outside of the pipeline 4 to achieve water and heat insulation.

[0058] It should also be noted that the metering module 8 is not only installed at the gas outlet of the gas-liquid separator 7, but also at the liquid outlet of the gas-liquid separator 7. The metering system measures the liquid flow rate while outputting the gas flow rate, thereby ensuring that the liquid flow rate output by the pipeline 4 can indeed be ignored during system operation.

[0059] Preferably, the metering module 8 includes a gas flow meter 8a, a container 8b, and an electronic balance 8c. The gas flow meter 8a is installed at the gas output end of the gas-liquid separator 7, the container 8b is installed at the liquid output end of the gas-liquid separator 7, and the container 8b is installed at the detection end of the electronic balance 8c. The gas flow meter 8a directly detects the volume of the gas, and the electronic balance 8c detects the weight of the liquid collected by the container 8b.

[0060] Further:

[0061] like Figure 2 As shown, this application also provides:

[0062] A method for simulating hydrate depressurization mining, the method using a system for simulating hydrate depressurization mining, the method comprising the following steps:

[0063] S5, use the thermostat module 5 to regulate the temperature of pipe 4;

[0064] S6, use back pressure module 6 to adjust the pressure at the outlet end of pipe 4 so that the pressure at the outlet end of pipe 4 is less than the pressure at the inlet end of pipe 4.

[0065] S7, inject hydrate into the inlet end of pipe 4;

[0066] S8 detects the temperature and pressure of various parts inside pipeline 4, and simultaneously measures the gas flow rate output by backpressure module 6.

[0067] Based on the above embodiments, the technical problem this application aims to solve is how to simulate the gas seepage process in hydrate depressurization mining. To this end, this application uses this system as experimental equipment. After performing the above steps, under the pressure difference between the inlet and outlet ends of pipeline 4, the gas continuously seeps within the porous medium filled inside pipeline 4, thereby achieving the experimental objective.

[0068] Further:

[0069] The system further includes a gas source and a liquid source, and the method further includes the following steps:

[0070] S2, measuring the porosity of porous media: evacuate the inside of pipe 4, use a liquid source to input liquid into the inlet of pipe 4, and record the volume of the input liquid when the pressure inside pipe 4 increases to the preset value.

[0071] S3, Measure the permeability of porous media: Use a liquid source to input liquid at a constant flow to the inlet end of pipe 4;

[0072] S4, Calculate the initial water saturation of the porous medium: Inject gas into the inlet of pipe 4 using a gas source until no more water comes out of the outlet of pipe 4, and record the volume of water displaced.

[0073] Based on the above embodiments, the technical problem this application aims to solve is how to adjust the properties of porous media to meet experimental requirements. To this end, this application uses the above method to test the airtightness of pipeline 4 and the porosity, permeability, and initial water saturation of the porous media, thereby enabling the porous media to simulate reservoirs with different porosities, permeabilities, and water saturations.

[0074] It should also be noted that the porous medium is composed of quartz sand of different particle sizes. After being washed, dried and crushed, it is loaded into pipeline 4 in batches and compacted using a sample compactor.

[0075] Further:

[0076] The method further includes the following steps:

[0077] S1, Test the airtightness of pipe 4: Seal the outlet end of pipe 4, use a gas source to input gas into the inlet end of pipe 4 and maintain pressure.

[0078] Based on the above embodiments, the technical problem that this application aims to solve is how to ensure that the airtightness of pipeline 4 is up to standard.

[0079] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A method for simulating hydrate depressurization mining, characterized in that, The method uses a simulated hydrate depressurization extraction system, which includes a pipeline (4), a constant temperature module (5), a back pressure module (6), a metering module (8), a data acquisition module, a gas source, and a liquid source. The pipeline (4) has an inlet end and an outlet end. The gas source and the liquid source are both connected to the inlet end of the pipeline (4). The pipeline (4) includes multiple pipes that are sequentially connected to each other. The pipes are detachably connected. The interior of the pipeline (4) is filled with a porous medium, and the exterior of the pipeline (4) is wrapped with insulation material. The constant temperature module (5) is used to keep the pipeline (4) at a constant temperature. The input end of the back pressure module (6) is connected to the outlet end of the pipeline (4). The metering module (8) is used to measure the gas flow rate output by the back pressure module (6). The data acquisition module is used to collect the pressure at the inlet and outlet ends of the pipeline (4) as well as the temperature and pressure of various parts inside the pipeline (4) to determine whether the decomposed hydrate has formed secondary hydrate or ice inside the porous medium. The method includes the following steps: S1, Test the airtightness of pipeline (4): Seal the outlet end of pipeline (4), use a gas source to input gas into the inlet end of pipeline (4) and maintain pressure; S2, measuring the porosity of porous media: evacuate the inside of the pipe (4), use a liquid source to input liquid into the inlet end of the pipe (4), and record the volume of the input liquid when the pressure inside the pipe (4) increases to the preset value; S3, Measure the permeability of porous media: Use a liquid source to input liquid at a constant flow to the inlet end of the pipe (4); S4, calculate the initial water saturation of the porous medium: use a gas source to inject gas into the inlet end of the pipe (4) until no more water comes out of the outlet end of the pipe (4), and record the volume of water displaced. S5, use the thermostat module (5) to adjust the temperature of the pipeline (4); S6, use back pressure module (6) to adjust the pressure at the outlet end of pipeline (4) so ​​that the pressure at the outlet end of pipeline (4) is less than the pressure at the inlet end of pipeline (4); S7, inject hydrate into the inlet end of pipe (4); S8 detects the temperature and pressure of various parts inside the pipeline (4), and measures the gas flow rate output by the back pressure module (6) to determine whether the decomposed hydrate has formed secondary hydrate or ice inside the porous medium.

2. The method for simulated hydrate depressurization mining according to claim 1, characterized in that, The system also includes a gas-liquid separator (7), the input end of which is connected to the output end of the back pressure module (6), and the metering module (8) is located at the gas outlet end of the gas-liquid separator (7).

3. The method for simulated hydrate depressurization mining according to claim 2, characterized in that, The gas source includes a gas storage cylinder (1) and a first constant speed and constant pressure module (2). The first constant speed and constant pressure module (2) includes a gas booster pump (2a), a high-pressure storage tank (2b), a pressure regulating valve (2c), and a flow controller (2d). The output end of the gas storage cylinder (1) is connected to the input end of the high-pressure storage tank (2b) through the gas booster pump (2a). The output end of the high-pressure storage tank (2b) is connected to the inlet end of the pipeline (4) in sequence through the pressure regulating valve (2c) and the flow controller (2d).

4. The method for simulated hydrate depressurization mining according to claim 1, characterized in that, The thermostat module (5) includes a combined bath and a refrigeration module, and the pipeline (4) is installed inside the thermostat module (5).

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