Gas-liquid separator for coal bed gas drainage and production well

Abstract

The utility model discloses a gas-liquid separator for a coal bed gas drainage and production well, which comprises a separator shell, a silk screen filter is mounted in the separator shell, a sealing partition plate is arranged on the inner side of the silk screen filter and in the middle of the bottom of the separator shell, a liquid inlet is formed in the upper position of the outer shell, and a liquid outlet is formed in the lower position of the outer shell. A blow-off pipe is arranged at the lower position of the outer shell; the gas-liquid separation device is simple in overall structure, reliable in operation and low in manufacturing cost, the silk screen filter is arranged in the gas-liquid separation device, the desorption rate of coal bed gas is increased, metering errors caused by the fact that the flowmeter is blocked by pulverized coal and fracturing sand can be reduced, and the gas-liquid separation device is suitable for being applied to the gas-liquid separation process of flow-back liquid of a coal bed gas drainage and production well on a large scale; meanwhile, a liquid level meter is arranged to monitor the liquid level in the separator in real time, and if the liquid level is abnormal, the liquid level is adjusted through a liquid level adjusting pipeline; therefore, different adjustment strategies can be adopted according to different liquid level heights of the liquid in the separator.

Description

Technical Field

[0001] The utility model relates to the technical field of coalbed methane drainage and production, in particular to a gas-liquid separator for a coalbed methane drainage and production well. Background Art

[0002] my country boasts abundant coalbed methane reserves, with total coalbed methane resources at a depth of less than 2,000 meters reaching 36.81 trillion cubic meters, and recoverable resources reaching 10 trillion cubic meters. This offers enormous potential for future development and is a key pillar of my country's rapid economic development and energy security.

[0003] The extraction of coalbed methane is different from the extraction of conventional natural gas. More than 80% of the coalbed methane in the coal seam exists in the coal matrix in the form of adsorption, and less than 20% of the coalbed methane is in a free state or dissolved in formation water. In order to desorb the coalbed methane in the coal seam, the reservoir pressure must be reduced. The only way to reduce the reservoir pressure is to lower the liquid level of the coalbed methane well. When the downhole liquid level is lowered, a pressure drop funnel will be formed with the wellbore as the center. When the coal seam pressure drops to the critical desorption pressure of the coalbed methane, the coalbed methane begins to desorb from the matrix. The desorbed coalbed methane passes through the cleats, cracks and wellbore in turn, and is then produced from the casing.

[0004] During the CBM production phase, the flowback fluid contains not only CBM but also large amounts of fracturing sand and pulverized coal. The CBM originates primarily from three sources: First, due to the high bottomhole pressure, CBM dissolves readily in formation water (at room temperature, at a pressure of 4 MPa, the concentration of CBM in each cubic meter of water is 1.24 cubic meters). Second, due to the inherent efficiency of the gas-liquid separation system in the downhole gas anchor, a small amount of CBM bubbles are carried into the pump body by the flowback fluid and subsequently discharged through the surface outlet. Third, when the tubing is perforated due to corrosion or screw wear, the flowback fluid pressure at the perforation falls below the casing pressure, allowing CBM to enter the flowback pipe. Fracturing sand and pulverized coal are primarily introduced into the wellbore by the two-phase flow of formation water and CBM seeping through the fractures. As the flowback fluid is removed, the pulverized coal and fracturing sand are gradually transported to the pump intake and ultimately discharged through the surface outlet.

[0005] In summary, since the flowback fluid contains coalbed methane, fracturing sand, and coal dust, directly discharging it into the environment would not only waste coalbed methane resources but also pose certain safety risks. The presence of fracturing sand and coal dust can cause large errors in the liquid flow meter, hindering precise control of the production process. Therefore, gas-liquid separation is necessary before the flowback fluid is discharged into the environment. Existing gas-liquid separators on the market have the disadvantages of being large, expensive, and requiring a high installation environment.

[0006] Based on the problems existing in the sand shovel in the above-mentioned prior art, the utility model proposes a gas-liquid separator for coalbed methane drainage wells to solve the above-mentioned shortcomings. Utility Model Content

[0007] The technical problem to be solved by the utility model is: how to solve the shortcomings of the existing gas-liquid separator, such as large volume, high price and high requirements for the installation environment.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] A gas-liquid separator for coalbed methane drainage wells includes a separator shell, a wire mesh filter is installed inside the separator shell, a sealing plate is provided on the inner side of the wire mesh filter and in the middle position of the bottom of the separator shell, a liquid inlet is provided at an upper position of the outer shell, and a sewage pipe is provided at a lower position of the outer shell.

[0010] The top of the outer shell is connected to the coalbed methane outlet pipe, and a liquid outlet is opened in the middle position of the bottom plate. A liquid level gauge for liquid level monitoring is provided on the outside of the outer shell, and the liquid outlet is connected to the liquid level regulating pipeline located on the outside of the outer shell.

[0011] The overall structure of this application is simple, the operation is reliable, the manufacturing cost is low, and it contains a wire mesh filter inside, which not only improves the desorption rate of coalbed methane, but also reduces the metering error caused by the blockage of the flow meter by coal powder and fracturing sand. It is suitable for large-scale application in the gas-liquid separation process of the return liquid of coalbed methane drainage wells; at the same time, a liquid level gauge is set to monitor the liquid level in the separator in real time. If the liquid level is abnormal, the liquid level is adjusted through the liquid level regulating pipeline; thus, different adjustment strategies can be adopted according to the different liquid level heights of the liquid in the separator.

[0012] As a further solution of the present invention: a cover plate is provided on the top of the separator housing, a base plate is provided on the bottom of the separator housing, and an outer shell is provided between the cover plate and the base plate.

[0013] As a further solution of the present invention: the separator shell is an overall cylindrical structure, and the wire mesh filter and the partition plate are both surrounded by a cylindrical structure.

[0014] As a further solution of the present invention: the two ports of the liquid level meter are respectively connected to an upper position of the separator housing and a lower position of the separator housing.

[0015] As a further solution of the present invention: the liquid level gauge is provided with five sections from bottom to top, namely low liquid level warning area, low liquid level early warning area, ideal liquid level area, high liquid level early warning area and high liquid level warning area.

[0016] As a further solution of the present invention: the liquid level regulating pipeline includes a horizontal pipe section, a vertical pipe section, an inverted "U"-shaped pipe section and a liquid outlet pipe, wherein the liquid outlet is connected to one end of the horizontal pipe section, the other end of the horizontal pipe section is connected to the bottom of the vertical pipe section, the top of the vertical pipe section is connected to the inverted "U"-shaped pipe section, and the other end of the inverted "U"-shaped pipe section is connected to the liquid outlet pipe;

[0017] An atmosphere communication port is provided at the top of the inverted "U"-shaped pipe section.

[0018] As a further solution of the present invention: the height of the inverted "U"-shaped pipe section is greater than or equal to 10 cm.

[0019] As a further solution of the present invention: a liquid flow meter is installed in the horizontal pipe section.

[0020] As a further solution of the present invention: a check valve is installed inside the coalbed methane outlet pipe.

[0021] As a further solution of the present invention: a ball valve is installed inside the sewage pipe.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This application has a simple overall structure, reliable operation, low manufacturing cost, and contains an internal wire mesh filter, which not only improves the desorption rate of coalbed methane, but also reduces the metering error caused by clogging of the flowmeter by coal powder and fracturing sand. It is suitable for large-scale application in the gas-liquid separation process of return fluid in coalbed methane drainage wells.

[0024] 2. This application sets a liquid level gauge to monitor the liquid level in the separator in real time, and can observe the liquid height in the separator. If the liquid level is abnormal, the liquid level can be adjusted through the liquid level regulating pipeline; thus, different adjustment strategies can be adopted according to the different liquid level heights in the separator to achieve precise liquid level adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a front view of a gas-liquid separator dedicated to coalbed methane drainage and production wells according to an embodiment of the utility model;

[0026] Figure 2 This is a side view of a gas-liquid separator dedicated to coalbed methane drainage wells according to an embodiment of the present utility model;

[0027] Figure 3 This is a top view of a gas-liquid separator dedicated to coalbed methane drainage and production wells according to an embodiment of the utility model;

[0028] Description of reference numerals:

[0029] 1. Coalbed methane outlet pipe; 2. Check valve; 3. Atmospheric connection port; 4. Liquid outlet pipe; 5. Vertical pipe section; 6. Cover plate; 7. Liquid inlet; 8. Outer shell; 9. Bottom plate; 10. Wire mesh filter; 11. Seal plate; 12. Liquid flow meter; 13. Ball valve; 14. Drain pipe; 15. Support;

[0030] 16. Liquid level gauge; 161. Low liquid level warning zone; 162. Low liquid level warning zone; 163. Ideal liquid level zone; 164. High liquid level warning zone; 165. High liquid level warning zone;

[0031] 17. Liquid outlet. DETAILED DESCRIPTION

[0032] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] Example 1

[0034] Reference Figure 1 、 Figure 2 and Figure 3 A gas-liquid separator for coalbed methane drainage wells includes a separator shell, wherein a cover plate 6 is provided on the top of the separator shell, a bottom plate 9 is provided on the bottom, an outer shell 8 is provided on the outside, and the separator shell is an overall cylindrical structure, and a support 15 is also installed at the bottom of the bottom plate 9;

[0035] Furthermore, a coalbed methane outlet pipe 1 is detachably connected to the upper side of the cover plate 6 by a thread, and a check valve 2 is installed on the coalbed methane outlet pipe 1 to prevent the coalbed methane from being discharged into the environment through the gas-liquid separator of the present application when the pressure in the coalbed methane pipeline is too high.

[0036] Reference Figure 1 A liquid inlet 7 is provided at the upper portion of the side wall of the outer shell 8. After the liquid inlet 7 enters the separator, it is connected to a short vertical pipe through a bend to prevent the return liquid from directly flushing the wire mesh filter 10 and causing damage to the filter.

[0037] Furthermore, a sewage pipe 14 is provided at an upper position of the side wall of the outer wall 8 of the separator, and a ball valve 13 is installed on the sewage pipe 14 to control the valve.

[0038] Reference Figure 1 、 Figure 2 and Figure 3A liquid outlet 17 is provided at the center of the bottom plate 9. The liquid outlet 17 is connected to the front end of the separator of the present application through a pipeline, and is connected to the vertical pipe section 5 through a horizontal pipe section. A liquid flow meter 12 is installed on the horizontal pipe section. The vertical pipe section 5 is connected to the liquid outlet pipe 4 through an inverted "U"-shaped pipe section. The height h of the inverted "U"-shaped pipe section can be adjusted according to the air pressure of the air outlet pipe, and an atmospheric communication port 3 is provided at the top of the inverted "U"-shaped pipe section. The purpose is to avoid the siphon effect of the liquid in the inverted U-shaped pipe when the liquid discharge volume is too large, resulting in the failure of the pressurization in the separator through the vertical pipe liquid column, thereby causing a large fluctuation in the air pressure in the gas-liquid separator;

[0039] Furthermore, the height of the atmosphere communication port 3 is not less than 10 cm. When the height is too low, the liquid is likely to splash out of the tube. All pipes and equipment between the liquid outlet hole 17 and the liquid outlet pipe 4 are threadedly connected to facilitate assembly and disassembly.

[0040] Reference Figure 1 、 Figure 2 and Figure 3 , the outer side of the liquid outlet 17 of the separator bottom plate 9 is a partition plate 11, and the partition plate 11 is a cylindrical structure;

[0041] There are two purposes for installing the isolation plate 11. One is to allow the return fluid to have an upward journey after entering the wire mesh filter 10, which is conducive to the upward migration of the desorbed gas to the gas phase space; the other is to allow the coal powder or fracturing sand that is not filtered by the wire mesh filter 10 to settle outside the isolation plate 11, thereby reducing the amount of fluid entering the liquid flow meter 12.

[0042] Furthermore, the outer side of the sealing plate 11 of the separator bottom plate 9 is a wire mesh filter 10 , which is a cylindrical structure. The wire mesh filter 10 contacts the cover plate 6 on the top and contacts the bottom plate 9 on the bottom.

[0043] It should be noted that the mesh size of the wire mesh filter 10 can be determined comprehensively based on the sand return situation of the return fluid and the water quality requirements of the liquid flow meter (the filtration diameter of the 100-mesh screen is 0.18 mm, the filtration diameter of the 200-mesh screen is 0.08 mm, and the filtration diameter of the 300-mesh screen is 0.044 mm); the wire mesh filter 10 has two functions, one is to filter the fracturing sand and coal powder in the return fluid, and the other is to capture small coalbed methane bubbles desorbed from the produced fluid. When the small coalbed methane bubbles pass through the screen, they cannot pass through the screen due to the effect of interfacial tension. The bubbles will adhere to the screen and then continue to gather into large bubbles. When the buoyancy of the bubble is greater than the adhesion force, the bubble will rise to the gas phase space and then be produced through the coalbed methane outlet pipe 1.

[0044] Reference Figure 2A liquid level gauge 16 is installed on the outer shell 8. The two ports of the liquid level gauge 16 are respectively connected to the upper position and the lower position of the separator shell. The liquid level gauge 16 is divided into five sections, namely the low liquid level warning area 161, the low liquid level warning area 162, the ideal liquid level area 163, the high liquid level warning area 164, and the high liquid level warning area 165. The purpose of the division is to be able to observe the liquid height in the separator and to be able to adopt different adjustment strategies according to the different liquid level heights of the liquid in the separator.

[0045] The specific operating principles of this application are as follows:

[0046] During use, the return fluid enters from the liquid inlet 7 and falls vertically, and then the liquid enters between the wire mesh filter 10 and the outer shell 8. Subsequently, the liquid is filtered through the wire mesh filter 10 to filter out the fracturing sand and coal powder in the return fluid, while capturing the small bubbles of coalbed methane desorbed from the produced fluid. The filtered liquid enters between the partition plate 11 and the wire mesh filter 10. At this time, the coal powder or fracturing sand that is not filtered by the screen settles to the outside of the partition plate 11, reducing the amount of coal powder or fracturing sand that enters the partition plate 11. The coal powder or fracturing sand that is filtered out by the screen is directly isolated between the wire mesh filter 10 and the outer shell 8.

[0047] The filtered liquid then overflows into the interior of the partition plate 11 and can finally be discharged from the liquid outlet 17 as needed;

[0048] During operation, the liquid level meter 16 performs liquid level detection. When the liquid level is in the low liquid level warning zone 161, it indicates that the liquid level in the separator is too low, which will cause the water containing dissolved coalbed methane to stay in the separator for too short a time, which is not conducive to the full desorption of coalbed methane. Moreover, when the liquid level is lower than the height of the internal baffle plate 11, there is a risk of gas cross-talk (the coalbed methane separated in the separator flows out from the liquid outlet 17). At this time, it is necessary to increase the height of the inverted U-shaped pipe section to increase the liquid level in the separator.

[0049] When the liquid level is in the high liquid level warning zone 165, it indicates that the liquid level in the separator is too high, which makes the gas space smaller. When the wellhead liquid output changes or the gas pressure changes, there is a risk of liquid overflowing from the coalbed methane outlet, and it is not conducive to maintaining the pressure stability of the coalbed methane. At this time, it is necessary to lower the height of the inverted U-shaped pipe section to lower the liquid level in the separator.

[0050] The separator should not be operated with the liquid level in the low level warning zone 162 or the high level warning zone 164. If the separator liquid level is operating in this zone, daily monitoring should be strengthened. If the liquid level moves from the warning zone to the alert zone, immediate adjustment measures should be taken. The separator liquid level should be kept in the ideal level zone 163 as much as possible.

[0051] Example 2

[0052] In order to explain this application more clearly, the important parameters involved in this application are described as follows:

[0053] Pressure inside the gas-liquid separator: The height difference between the liquid outlet 4 and the lowest liquid level is 0.5m, and the height h of the inverted U-shaped pipe section ranges from 0 to 2.5 meters. The maximum height difference between the highest liquid level of the inverted U-shaped pipe section and the liquid level in the separator is 3.0m. The maximum air pressure in the separator is 29.4kPa. In order to ensure that the equipment can operate well when the air pressure fluctuates, a safety factor of 1.1 is taken. At this time, the maximum air pressure in the gas-liquid separator is 26.7kPa.

[0054] Desorption time of flowback liquid in gas-liquid separator: According to research, after coalbed methane enters the normal drainage stage, the daily liquid production of more than 95% of the drainage wells is less than 30m3. 3 / d, the diameter of the gas-liquid separator tank is 1m, the tank height is 1.3m, when the liquid level in the tank is at the lowest level of the ideal liquid level zone 163, the volume in the tank is 0.471m 3 At this time, the minimum residence time of the produced liquid in the tank is 23 minutes, the free gas in the produced liquid can be completely separated, and the amount of methane dissolved in 10 minutes can be reduced to 1.2 times the solubility of methane in water at this temperature and pressure. When the temperature is 20°C and the pressure is 126kPa, the solubility of methane in water is 0.018L / m 3 At this time, the methane content of the liquid flowing out of the liquid outlet is less than 0.0216L / m 3 .

[0055] Screen flow rate: When the diameter of the wire mesh filter 10 is 0.6m and the liquid level is 0.6m, the screen flow section is 1.13m 2 When the liquid production rate is 30m 3 / d, the screen flow rate is 0.03㎝ / s. Therefore, the screen flow rate is extremely slow, which is conducive to capturing small bubbles of coalbed methane precipitated from the liquid flow and blocking the passage of fracturing sand and coal powder.

[0056] In summary, this technology overcomes the shortcomings of traditional gas-liquid separators, which are large in size and expensive, and has better gas-liquid separation effect.

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A gas-liquid separator for a coalbed methane drainage well, comprising a separator housing, characterized in that: A wire mesh filter (10) is installed inside the separator housing, a sealing plate (11) is provided inside the wire mesh filter (10) and at the middle position of the bottom of the separator housing, a liquid inlet (7) is provided at an upper position of the outer housing (8), and a sewage discharge pipe (14) is provided at a lower position of the outer housing (8); The top of the outer shell (8) is connected to the coalbed methane outlet pipe (1), a liquid outlet hole (17) is provided at the middle position of the bottom plate (9), a liquid level meter (16) for liquid level monitoring is provided on the outside of the outer shell (8), and the liquid outlet hole (17) is connected to a liquid level regulating pipeline located on the outside of the outer shell (8).

2. The gas-liquid separator for coalbed methane drainage well according to claim 1, characterized in that: A cover plate (6) is provided on the top of the separator shell, a bottom plate (9) is provided on the bottom of the separator shell, and an outer shell (8) is provided between the cover plate (6) and the bottom plate (9).

3. The gas-liquid separator for coalbed methane drainage well according to claim 1, characterized in that: The separator shell is in a cylindrical structure as a whole, and the wire mesh filter (10) and the partition plate (11) are both surrounded by a cylindrical structure.

4. The gas-liquid separator for coalbed methane drainage well according to claim 1, characterized in that: The two ports of the liquid level meter (16) are respectively connected to an upper position of the separator housing and a lower position of the separator housing.

5. The gas-liquid separator for coalbed methane drainage well according to claim 4, characterized in that: The liquid level gauge (16) is provided with five sections from bottom to top, namely a low liquid level warning area (161), a low liquid level early warning area (162), an ideal liquid level area (163), a high liquid level early warning area (164) and a high liquid level warning area (165).

6. The gas-liquid separator for coalbed methane drainage well according to claim 1, characterized in that: The liquid level regulating pipeline comprises a horizontal pipe section, a vertical pipe section (5), an inverted "U"-shaped pipe section and a liquid outlet pipe (4), wherein the liquid outlet hole (17) is connected to one end of the horizontal pipe section, the other end of the horizontal pipe section is connected to the bottom of the vertical pipe section (5), the top of the vertical pipe section (5) is connected to the inverted "U"-shaped pipe section, and the other end of the inverted "U"-shaped pipe section is connected to the liquid outlet pipe (4); An atmosphere communication port (3) is provided at the top of the inverted "U"-shaped pipe section.

7. The gas-liquid separator for coalbed methane drainage well according to claim 6, characterized in that: The height of the inverted "U"-shaped pipe section is greater than or equal to 10 cm.

8. The gas-liquid separator for coalbed methane drainage well according to claim 6, characterized in that: A liquid flow meter (12) is installed in the horizontal pipe section.

9. The gas-liquid separator for coalbed methane drainage well according to claim 1, characterized in that: A check valve (2) is installed inside the coalbed methane outlet pipe (1).

10. The gas-liquid separator for coalbed methane drainage well according to claim 1, characterized in that: A ball valve (13) is installed inside the sewage pipe (14).

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