Coal bed gas well excitation elutriation test device and test method thereof

Abstract

The application discloses a coal bed gas well excitation elutriation test equipment and a test method thereof. The equipment comprises a water storage tank, two communication pipes are communicated with the two sides of the water storage tank, a connecting main pipe is communicated with the water storage tank through the left communication pipe, a flowmeter is connected between the communication pipe and the connecting main pipe, a gas injection pipe column is communicated with the lower end of the connecting main pipe, a large oil pipe is inserted into the gas injection pipe column, the large oil pipe is communicated with the connecting main pipe, and a pressure gauge is installed at the bottom end of the gas injection pipe column. The application has the beneficial effect that in the production process, a high-pressure gas source is used to apply pulse gas pressure to the reservoir, the raw coal sample is broken, the coal sample permeability is improved, the high-pressure gas is pressed into the reservoir through coal fissures, fractured sand fissures and the like, the reservoir potential energy is increased, the coal powder and coal slime blocked in the coal fissures are carried to the wellbore through high-speed water flow, the coal powder, coal slime and a small amount of fractured sand in the wellbore are carried to the ground along the oil pipe, and the coal powder, coal slime and fractured sand are separated through a water-gas separation tank.

Description

Technical Field

[0001] This invention relates to a specific equipment and method for stimulating and washing coalbed methane wells, belonging to the field of coalbed methane exploration technology. Background Technology

[0002] Xinjiang is an important resource area for coalbed methane exploration and development in my country, with a predicted resource volume of 9.6 trillion cubic meters, indicating huge resource potential. Moreover, coalbed methane, with its advantages of being clean, efficient, and pollution-free, plays an important role in supplementing Xinjiang's energy structure.

[0003] Due to factors such as the abundance of coal seams, large dip angles, complex geological structures, and strong reservoir heterogeneity in Xinjiang, problems such as low average production per well, a small proportion of high-yield wells, and rapid decline in gas production are prominent, severely restricting the large-scale development of coalbed methane.

[0004] Currently, the common method for coalbed methane well extraction both domestically and internationally is drainage and depressurization extraction. As coalbed methane wells are extracted, during the water and gas production process, raw coal dust from the coal reservoir, coal dust generated during fracturing, and drilling pollutants will flow into the wellbore along with the water, causing blockage of the near-wellbore reservoir channels, resulting in a significant reduction in coal seam permeability, which in turn affects gas production and leads to a significant decrease in production.

[0005] Slot blockage and sandless filling of coalbed methane wells are among the main reasons for the rapid decline in gas production in coalbed methane development areas. In particular, the pressure difference near the well is large, and the blockage is more serious. In most low-production wells, although the coal seam gas content is high, there is a lack of effective gas production channels, and the production capacity cannot be released. Therefore, we propose a coalbed methane well excitation flushing test equipment and its test method. Summary of the Invention

[0006] The purpose of this invention is to provide a test device and test method for stimulating the washing of coalbed methane wells in order to solve the above-mentioned problems.

[0007] The present invention achieves the above-mentioned objectives through the following technical solution: a coalbed methane well excitation flushing test device and its test method, comprising a water storage tank, two connecting pipes on both sides of the water storage tank, a connecting main pipe connected to the water storage tank through the left connecting pipe, a flow meter connected between the connecting pipe and the connecting main pipe, an injection pipe string connected to the lower end of the connecting main pipe, the injection pipe string being inserted into the well, a large oil pipe inserted inside the injection pipe string, the large oil pipe being connected to the connecting main pipe, and a pressure gauge installed at the bottom end of the injection pipe string.

[0008] Preferably, the lower end of the water storage tank is connected to a sewage pipe, which is connected to the sewage inlet pool.

[0009] Preferably, the water storage tank is connected to a ground plunger pump via a connecting pipe on the right side, the outer surface of the ground plunger pump is connected to a flow pipe, and the outer surface of the ground plunger pump is connected to a frequency converter via an electric wire.

[0010] Preferably, the flow pipe is connected to the connecting main pipe, a flow control valve is provided between the flow pipe and the connecting main pipe, an air inlet line is provided on the outer surface of the connecting main pipe, and the air inlet line is connected to the air injection column.

[0011] Preferably, the gas injection string includes a surface casing and a production casing, the surface casing is fixedly connected to the upper surface of the production casing, the surface casing is in contact with the surface, and the production casing is in contact with the coal reservoir.

[0012] Preferably, the outer surface of the production sleeve is provided with perforations #39, #40, #41, #42, #43, and #44.

[0013] Preferably, the outer surface of the production sleeve is provided with perforations #39, #41, and #42.

[0014] Preferably, the outer surface of the production casing is provided with perforations #39, #41 and #42, a small oil pipe is sleeved inside the large oil pipe, and a sand settling material is provided below the small oil pipe.

[0015] The beneficial effects of this invention are as follows: During the production process, a high-pressure gas source is used to apply pulsed gas pressure to the reservoir, causing periodic strain in the coal and rock. The volumetric strain of the coal exhibits an expansion-contraction-expansion pattern. As the number of fatigue cycles increases, the raw coal sample will fracture, generating a large number of macroscopic fractures within the sample, greatly improving its permeability. During production, a force greater than the reservoir pressure is applied to the reservoir using the high-pressure gas source, forcing high-pressure gas into the reservoir through coal fractures and fracturing sand fissures, increasing the reservoir's potential energy. Once a certain level is reached, the accumulated gas potential energy in the reservoir is used to release coal powder and sludge trapped in the coal fractures into the wellbore. During production, a jet pump, utilizing the Venturi effect, draws water, coal powder, sludge, and sand from the wellbore into the tubing. High-speed water flow carries the coal powder, sludge, and a small amount of fracturing sand from the wellbore to the surface, where they are separated by a water-gas separator. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] Figure 2 This is a schematic diagram of reservoir powder removal according to the present invention;

[0018] Figure 3 This is a schematic diagram showing the depth of the unblocking tubing string in well FS-81 of the present invention.

[0019] Figure 4 This is a schematic diagram of the well casing insertion structure for the FS-23 well of the present invention;

[0020] Figure 5 This is a schematic diagram of the well casing structure for the FS-25 well of the present invention.

[0021] In the diagram: 1. Water storage tank; 101. Sewage pipe; 102. Connecting pipe; 2. Ground plunger pump; 201. Frequency converter; 202. Flow pipe; 3. Flow control valve; 301. Flow meter; 4. Connecting main pipe; 401. Air inlet line; 5. Pressure gauge; 6. Air injection string; 61. Surface casing; 62. Production casing; 601. Main oil pipe; 602. Small oil pipe; 701. Perforation #39; 702. Perforation #40; 703. Perforation #41; 704. Perforation #42; 705. Perforation #43; 706. Perforation #44; 8. Sedimentation. Detailed Implementation

[0022] 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.

[0023] This invention discloses a test device and test method for induced flushing of coalbed methane wells.

[0024] According to the appendix Figure 1-3 As shown, the well includes a water storage tank 1, with two connecting pipes 102 on both sides of the water storage tank 1. The water storage tank 1 is connected to a connecting main pipe 4 through the left connecting pipe 102. A flow meter 301 is connected between the connecting pipe 102 and the connecting main pipe 4. An air injection string 6 is connected to the lower end of the connecting main pipe 4 and is inserted into the well.

[0025] The gas injection string 6 has a large oil pipe 601 inserted inside, which is connected to the main pipe 4. A pressure gauge 5 is installed at the bottom of the gas injection string 6.

[0026] The lower end of the water storage tank 1 is connected to a sewage pipe 101, which is connected to the sewage inlet pool.

[0027] Water storage tank 1 is connected to ground plunger pump 2 via right-side connecting pipe 102. Ground plunger pump 2 is connected to flow pipe 202 via outer surface. Ground plunger pump 2 is connected to frequency converter 201 via wire via outer surface.

[0028] The flow pipe 202 is connected to the connecting main pipe 4. A flow control valve 3 is installed between the flow pipe 202 and the connecting main pipe 4. An air inlet line 401 is opened on the outer surface of the connecting main pipe 4. The air inlet line 401 is connected to the air injection column 6.

[0029] The gas injection string 6 includes a surface casing 61 and a production casing 62. The surface casing 61 is fixedly connected to the upper surface of the production casing 62. The surface casing 61 is in contact with the surface, and the production casing 62 is in contact with the coal reservoir.

[0030] The outer surface of the production sleeve 62 is provided with perforations 701 (39#), 702 (40#), 703 (41#), 704 (42#), 705 (43#), and 706 (44#).

[0031] Working principle: When conducting a gas well induced flushing test, the operation of the surface plunger pump 2 is first checked, the powder and sand removal tubing is lowered, the wellbore is cleaned, and the wellbore working environment is ensured to be safe.

[0032] At this point, the gas injection string 6 is lowered into the wellbore, so that the gas injection string 6 is lowered to the upper boundary of the coal seam. At this time, the surface casing 61 is tightly attached to the surface, and the production casing 62 is tightly attached to the coal reservoir.

[0033] At this time, the ground compressor is started, and air is injected through the air inlet pipe 401. The air then enters the gas injection string 6 through the connecting main pipe 4. The pump truck is started, and water is injected through the main oil pipe 601. When the pressure gauge 5 monitors that the pressure in the well reaches the design value, the compressor stops injecting gas. Through the pulse high pressure, a large number of new irregular macro fractures are formed on the coal reservoir, which greatly improves the permeability of the coal reservoir. The gas is used to store energy in the reservoir, and the gas is controlled to enter slowly and exit quickly, carrying water and coal powder into the wellbore.

[0034] Manually open the gate valve of the gas-liquid separator, remotely start the electric gate valve, and accurately and quickly release the fluid through perforations 39# 701, 40# 702, 41# 703, 42# 704, 43# 705, and 44# 706. Utilize jet pumps and water injection devices to carry water and coal dust to the surface during the drainage process, impacting and washing away unstable fracturing sand and adhered coal dust particles, thus reducing the risk of pump jamming during drainage.

[0035] The injected coal powder enters the connecting pipe 102 through the gas injection string 6, and then is discharged into the sewage pool through the water storage tank 1 and the sewage discharge pipe 101. At this time, the discharge of coal powder from the sewage pool is observed to determine the number of cycles, ensure that the flushing is completed, and then the well repair, cleaning and unblocking process is completed. The gas injection string 6 is pulled out and the retrieval string is lowered to retrieve the coal powder.

[0036] According to the appendix Figure 1 , Figure 2 and Figure 4 As shown, the well includes a water storage tank 1, with two connecting pipes 102 on both sides of the water storage tank 1. The water storage tank 1 is connected to a connecting main pipe 4 through the left connecting pipe 102. A flow meter 301 is connected between the connecting pipe 102 and the connecting main pipe 4. An air injection string 6 is connected to the lower end of the connecting main pipe 4 and is inserted into the well.

[0037] The gas injection string 6 has a large oil pipe 601 inserted inside, which is connected to the main pipe 4. A pressure gauge 5 is installed at the bottom of the gas injection string 6.

[0038] The lower end of the water storage tank 1 is connected to a sewage pipe 101, which is connected to the sewage inlet pool.

[0039] Water storage tank 1 is connected to ground plunger pump 2 via right-side connecting pipe 102. Ground plunger pump 2 is connected to flow pipe 202 via outer surface. Ground plunger pump 2 is connected to frequency converter 201 via wire via outer surface.

[0040] The flow pipe 202 is connected to the connecting main pipe 4. A flow control valve 3 is installed between the flow pipe 202 and the connecting main pipe 4. An air inlet line 401 is opened on the outer surface of the connecting main pipe 4. The air inlet line 401 is connected to the air injection column 6.

[0041] The gas injection string 6 includes a surface casing 61 and a production casing 62. The surface casing 61 is fixedly connected to the upper surface of the production casing 62. The surface casing 61 is in contact with the surface, and the production casing 62 is in contact with the coal reservoir. The outer surface of the production casing 62 is provided with perforations 701 (39#), 703 (41#), and 704 (42#).

[0042] Working principle: When conducting a gas well induced flushing test, the operation of the surface plunger pump 2 is first checked, the powder and sand removal tubing is lowered, the wellbore is cleaned, and the wellbore working environment is ensured to be safe.

[0043] At this point, the gas injection string 6 is lowered into the wellbore, so that the gas injection string 6 is lowered to the upper boundary of the coal seam. At this time, the surface casing 61 is tightly attached to the surface, and the production casing 62 is tightly attached to the coal reservoir.

[0044] At this time, the ground compressor is started, and air is injected through the air inlet pipe 401. The air then enters the gas injection string 6 through the connecting main pipe 4. The pump truck is started, and water is injected through the main oil pipe 601. When the pressure gauge 5 monitors that the pressure in the well reaches the design value, the compressor stops injecting gas. Through the pulse high pressure, a large number of new irregular macro fractures are formed on the coal reservoir, which greatly improves the permeability of the coal reservoir. The gas is used to store energy in the reservoir, and the gas is controlled to enter slowly and exit quickly, carrying water and coal powder into the wellbore.

[0045] Manually open the gate valve of the gas-liquid separator, remotely start the electric gate valve, and accurately and quickly release the gas. The gas is released through the set perforation holes 39# 701, 41# 703 and 42# 704. Using the jet pump and water injection device, high-speed water flow is used during the drainage process to bring water and coal dust to the surface, impacting and washing out unstable fracturing sand and agglomerated coal dust and particles, reducing the risk of pump jamming during drainage.

[0046] The injected coal powder enters the connecting pipe 102 through the gas injection string 6, and then is discharged into the sewage pool through the water storage tank 1 and the sewage discharge pipe 101. At this time, the discharge of coal powder from the sewage pool is observed to determine the number of cycles, ensure that the flushing is completed, and then the well repair, cleaning and unblocking process is completed. The gas injection string 6 is pulled out and the retrieval string is lowered to retrieve the coal powder.

[0047] According to the appendix Figure 1 , Figure 2 and Figure 5 As shown, the well includes a water storage tank 1, with two connecting pipes 102 on both sides of the water storage tank 1. The water storage tank 1 is connected to a connecting main pipe 4 through the left connecting pipe 102. A flow meter 301 is connected between the connecting pipe 102 and the connecting main pipe 4. An air injection string 6 is connected to the lower end of the connecting main pipe 4 and is inserted into the well.

[0048] The gas injection string 6 has a large oil pipe 601 inserted inside, which is connected to the main pipe 4. A pressure gauge 5 is installed at the bottom of the gas injection string 6.

[0049] The lower end of the water storage tank 1 is connected to a sewage pipe 101, which is connected to the sewage inlet pool.

[0050] Water storage tank 1 is connected to ground plunger pump 2 via right-side connecting pipe 102. Ground plunger pump 2 is connected to flow pipe 202 via outer surface. Ground plunger pump 2 is connected to frequency converter 201 via wire via outer surface.

[0051] The flow pipe 202 is connected to the connecting main pipe 4. A flow control valve 3 is installed between the flow pipe 202 and the connecting main pipe 4. An air inlet line 401 is opened on the outer surface of the connecting main pipe 4. The air inlet line 401 is connected to the air injection column 6.

[0052] The gas injection string 6 includes a surface casing 61 and a production casing 62. The surface casing 61 is fixedly connected to the upper surface of the production casing 62 and is in contact with the surface. The production casing 62 is in contact with the coal reservoir.

[0053] The outer surface of the production casing 62 is provided with perforations 701 (39#), 703 (41#), and 704 (42#). A small oil pipe 602 is sleeved inside the large oil pipe 601, and a sand settling device 8 is provided below the small oil pipe 602.

[0054] A small oil pipe 602 is connected inside the large oil pipe 601. The small oil pipe 602 has a smaller outer diameter and can effectively pass through the deformed section and horizontal section of the gas injection string 6, thus minimizing risk.

[0055] An air compressor is used to fill the injection string 6 with air, and then the air compressor is used to inject air from the intake line 401 in reverse circulation to increase the pressure inside the well. Under the action of force, the air in the injection string 6 is continuously ejected to the wellhead, thereby driving the sand 8 at the bottom of the well to be ejected.

[0056] As the sand level decreases, the small tubing 602 automatically descends. Under the influence of air pressure, the sediment 8 and water at the bottom of the well first enter the small tubing 602, and then are carried to the surface through the large tubing 601. As the sand level decreases, the small tubing 602 loses the support of the sand level, and under the influence of the reverse force and gravity, the small tubing 602 gradually descends, and the sand flushing depth gradually increases.

[0057] To prevent the small oil pipe 602 from falling off, the small oil pipe 602 is located inside the large oil pipe 601. As the small oil pipe 602 falls, the special connector at the top of the small oil pipe 602 will be locked onto the coupling at the bottom of the large oil pipe 601, thus preventing the small oil pipe 602 from falling off.

[0058] Working principle: When conducting a gas well induced flushing test, the operation of the surface plunger pump 2 is first checked, the powder and sand removal tubing is lowered, the wellbore is cleaned, and the wellbore working environment is ensured to be safe.

[0059] At this point, the gas injection string 6 is lowered into the wellbore, so that the gas injection string 6 is lowered to the upper boundary of the coal seam. At this time, the surface casing 61 is tightly attached to the surface, and the production casing 62 is tightly attached to the coal reservoir.

[0060] At this time, the ground compressor is started and air is injected from the air inlet line 401. The air enters the air injection string 6 through the connecting main pipe 4 and fills the large oil pipe 601 and small oil pipe 602 with air. The pump truck is started and water is injected from the large oil pipe 601. When the pressure gauge 5 monitors that the pressure in the well reaches the design value, the flow meter 301 is opened. The bottom sand 8 and water are discharged back to the sewage tank through the small oil pipe 602 and the large oil pipe 601 in sequence.

[0061] As the sediment 8 descends, the small tubing 602 gradually descends until all the sediment 8 in the well is cleared out, the construction is completed, the well workover, cleaning and unblocking process is completed, the gas injection tubing 6 is pulled out, and the retrieval tubing is lowered to retrieve coal dust.

[0062] During production, a high-pressure gas source is used to apply pulsed gas pressure to the reservoir, causing periodic strain in the coal and rock. The volumetric strain of the coal exhibits an expansion-contraction-expansion pattern. As the number of fatigue cycles increases, the raw coal sample will fracture, generating numerous macroscopic fractures within the sample, significantly improving its permeability. During production, a force greater than the reservoir pressure is applied to the reservoir using the high-pressure gas source, forcing high-pressure gas into the reservoir through coal fractures and fracturing sand fissures, increasing the reservoir's potential energy. Once a certain level is reached, the accumulated gas potential energy is used to release coal dust and sludge trapped within the coal fractures into the wellbore. During production, a jet pump, utilizing the Venturi effect, draws water, coal dust, sludge, and sand from the wellbore into the tubing. High-speed water flow carries the coal dust, sludge, and a small amount of fracturing sand from the wellbore to the surface, where they are separated by a water-gas separator.

[0063] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A coalbed methane well excitation flushing test device, comprising a water storage tank (1), wherein two connecting pipes (102) are connected to both sides of the water storage tank (1), the water storage tank (1) is connected to a connecting main pipe (4) through the left connecting pipe (102), a flow meter (301) is connected between the connecting pipe (102) and the connecting main pipe (4), and an injection pipe string (6) is connected to the lower end of the connecting main pipe (4), the injection pipe string (6) being inserted into the well, characterized in that: The gas injection string (6) is internally connected to a large oil pipe (601), which is connected to the main pipe (4). A pressure gauge (5) is installed at the bottom of the gas injection string (6). The lower end of the water storage tank (1) is connected to a sewage pipe (101), which is connected to the sewage inlet pool. The water storage tank (1) is connected to a ground plunger pump (2) through a right-side connecting pipe (102). The outer surface of the ground plunger pump (2) is connected to a flow pipe (202). The outer surface of the ground plunger pump (2) is connected to a frequency converter (201) through an electric wire. The flow pipe (202) is connected to the connecting main pipe (4), and a flow control valve (3) is provided between the flow pipe (202) and the connecting main pipe (4). An air inlet line (401) is provided on the outer surface of the connecting main pipe (4), and the air inlet line (401) is connected to the air injection column (6). Air is injected into the air intake line (401), and water is injected into the large oil line (601).

2. The coalbed methane well excitation flushing test equipment according to claim 1, characterized in that: The gas injection string (6) includes a surface casing (61) and a production casing (62). The surface casing (61) is fixedly connected to the upper surface of the production casing (62). The surface casing (61) is in contact with the surface, and the production casing (62) is in contact with the coal reservoir.

3. The coalbed methane well excitation flushing test equipment according to claim 2, characterized in that: The outer surface of the production sleeve (62) is provided with perforations 39# (701), 40# (702), 41# (703), 42# (704), 43# (705) and 44# (706).

4. The coalbed methane well induced flushing test equipment according to claim 3, characterized in that: The outer surface of the production sleeve (62) is provided with perforations 39# (701), 41# (703) and 42# (704).

5. The coalbed methane well excitation flushing test equipment according to claim 4, characterized in that: The outer surface of the production casing (62) is provided with perforations 39# (701), 41# (703) and 42# (704). The large oil pipe (601) is fitted with a small oil pipe (602). A sand settling device (8) is provided below the small oil pipe (602).

6. The test method for a coalbed methane well induced flushing test device according to any one of claims 1-5, characterized in that: Includes the following steps: S1: Inspect the operation of the ground plunger pump (2), lower the powder and sand dredging tubing, clean the wellbore, and ensure the safety of the wellbore working environment; S2: At this time, the gas injection string (6) is lowered and aligned with the wellbore, so that the gas injection string (6) is lowered to the upper boundary of the coal seam. At this time, the surface casing (61) is tightly attached to the surface, and the production casing (62) is tightly attached to the coal reservoir. S3: At this time, start the ground compressor and inject air from the air inlet pipeline (401). At this time, the air enters the gas injection string (6) through the connecting main pipe (4). Start the pump truck and inject water from the main oil pipe (601). When the pressure gauge (5) monitors the pressure in the well and reaches the design value, stop the compressor to inject gas. Through the pulse high pressure, a large number of new irregular macro fractures are formed on the coal reservoir, thereby greatly improving the permeability of the coal reservoir. The gas is used to store energy in the reservoir, and the gas is controlled to enter slowly and exit quickly, carrying water and coal powder into the wellbore. S4: Manually open the gate valve of the gas-liquid separator, remotely start the electric gate valve, and accurately and quickly release the spray. Utilize the jet pump and water injection device to use high-speed water flow during the drainage process to bring water and coal powder to the ground, impacting unstable fracturing sand and agglomerated coal powder and coal particles, washing them out, and reducing the risk of pump jamming during drainage. S5: The pulverized coal is injected into the connecting pipe (102) through the gas injection string (6), and then discharged into the sewage pool through the water storage tank (1) and the sewage pipe (101). At this time, observe the discharge of pulverized coal from the sewage pool, determine the number of cycles, ensure that the flushing is completed, and then end the well repair, cleaning and unblocking process. Take out the gas injection string (6) and lower the retrieval string to retrieve the pulverized coal.

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