A safe drainage system for the annulus side of an underground gas storage

Abstract

The invention discloses a safety drainage system on the annulus side of an underground gas storage reservoir, and relates to the technical field of underground oil and gas production equipment. It includes an injection pipe and a drainage pipe, wherein the upper end of the injection pipe is located above the ground and is connected to the gas outlet end of a gas pressure pump station; the upper end of the drainage pipe is located above the ground and is connected to the water inlet end of a drainage pipeline; a pulse drainage chamber is connected to the injection and production pipe through a one-way valve; a gas-liquid mixing valve is arranged at the bottom of the pulse drainage chamber; the gas-liquid mixing valve includes an air chamber, a piston that cooperates with the air chamber in a sliding seal in the air chamber; the piston forms a sealed air pressure chamber with the bottom of the air chamber; the piston and the upper part of the air chamber form a gas-liquid mixing chamber; and a water inlet hole is arranged at the lower part of the side wall of the gas-liquid mixing chamber. The invention discharges the bottom hole liquid and gas through the annulus side, does not pass through the injection and production well column, does not require multi-stage gas lift valves to be connected in series, and does not cause safety risks to the annulus.

Description

Technical Field

[0001] The present invention relates to the technical field of underground oil and gas production equipment, and in particular to a bottom hole liquid discharge system for an underground gas storage reservoir, and may be related to an international patent classification number of E21B43 / 00. Background Art

[0002] Underground gas storage is the use of underground porous rock formations or closed caves to store natural gas. It is a relatively economical and safe method to store large amounts of natural gas. Its main function is to adjust the seasonal imbalance between gas supply and demand and ensure the needs of peak gas supply; to make long-distance gas pipelines and equipment operate in a balanced manner to improve the utilization rate of pipelines and equipment and reduce gas transmission costs; and to ensure gas supply in emergency situations such as accidents. Depleted oil and gas layers, underground aquifers and underground caves with good sealing properties can all be used as underground gas storage.

[0003] Liquid accumulation at the bottom of underground gas storage is a common problem, especially in the later stage of gas well production. Due to the decrease in formation pressure and gas well productivity, the temperature gradient of the wellbore increases, causing some components of natural gas to condense in the wellbore to form condensate. When the gas production of the gas well is not enough to carry out this part of the condensate, the condensate will fall back to the bottom of the well, forming liquid accumulation at the bottom of the well. This liquid accumulation phenomenon will increase the bottom of the well back pressure, reduce the production pressure difference, reduce gas production, and even cause the gas well to stop production.

[0004] A common method to deal with liquid accumulation at the bottom of the well is gas lift drainage. This method of gas lift drainage is to inject high-pressure gas into the annulus, which enters the injection and production tubing through the gas lift valve, thereby reducing the density of the fluid in the tubing, mixing the accumulated liquid with the gas to form a low-density bubble liquid, and then discharge the bubble liquid to the ground under the action of the gas pressure in the well.

[0005] Gas lift drainage is an effective means of bottom hole drainage, but this method causes the bottom hole liquid to pass through the entire injection and production well column in the form of bubble mixture. The hydrate contained in it will corrode the inner wall of the injection and production pipe column. In addition, the discharged bubble mixture needs to be separated by a separator, and the separation process will reduce the gas production efficiency. On the other hand, this gas lift drainage method requires the medium pressure to be transmitted through the annulus, and the annulus pressure will cause periodic pressure changes in the cement seal ring in the annulus, resulting in cracks and the risk of annulus seal failure. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a safe drainage system on the annulus side of an underground gas storage reservoir in response to the above-mentioned technical deficiencies. The system discharges the bottom hole liquid and gas through the annulus side without passing through the injection and production well column and without requiring multi-stage gas lift valves to be connected in series. The drainage process does not affect the normal gas production of the injection and production well column and does not cause changes in the annulus pressure, thereby ensuring the safety of the annulus seal.

[0007] The present invention provides an annulus-side safety drainage system for an underground gas storage reservoir, comprising an injection and production pipe string, an annulus casing located outside the injection and production pipe string, a gas pressure pump station located on the ground, and a drainage pipeline located on the ground; the space between the annulus casing and the injection and production pipe string is called an annulus; the bottom of the annulus is sealed by a packer; and the system comprises:

[0008] An air injection pipe and a liquid discharge pipe, wherein the upper end of the air injection pipe is located above the ground and is connected to the air outlet of the air pressure pump station; the upper end of the liquid discharge pipe is located above the ground and is connected to the water inlet of the drainage pipeline; the lower parts of both the air injection pipe and the liquid discharge pipe extend from the annulus to the top of the packer;

[0009] A pulse drainage chamber, which is arranged above the packer and at the bottom of the annulus, and is an annular chamber arranged outside the injection and production string. The pulse drainage chamber is connected to the injection and production string through a one-way valve; the conduction direction of the one-way valve is from the inner cavity of the injection and production string to the pulse drainage chamber;

[0010] A gas-liquid mixing valve is arranged at the bottom of the pulse discharge chamber; the gas-liquid mixing valve comprises an air chamber and a piston which is slidably sealed with the air chamber in the air chamber; the lower ends of the air injection pipe and the discharge pipe are both connected to the inner cavity of the air chamber; the upper end surface of the piston is sealed with the lower ends of the air injection pipe and the discharge pipe; the piston and the bottom of the air chamber form a sealed air pressure chamber; the piston and the upper part of the air chamber form a gas-liquid mixing chamber; a water inlet hole is arranged at the lower part of the side wall of the gas-liquid mixing chamber, and when the air pressure pump station pressurizes and supplies gas to the air injection pipe, the air pressure pushes the piston down to the water inlet hole, and at this time the water inlet hole connects the gas-liquid mixing chamber with the pulse discharge chamber.

[0011] To further optimize the technical solution, an air injection pipe and a liquid discharge pipe of a safety liquid discharge system on the annulus side of an underground gas storage reservoir are coaxially arranged, and the air injection pipe is located inside the liquid discharge pipe.

[0012] To further optimize the technical solution, a cluster pipe is evenly distributed circumferentially in the annular space between the drainage pipe and the gas injection pipe of a safety drainage system on the annular side of an underground gas storage reservoir, and the lower end of the cluster pipe is connected to the lower port of the drainage pipe, and the upper end is connected to the ground outlet of the drainage pipe.

[0013] To further optimize the technical solution, a portion of a drainage pipe of a safety drainage system on the annulus side of an underground gas storage reservoir above the ground is installed with an A limiting valve; the A limiting valve limits the flow rate of the medium in the drainage pipe by changing the opening, so as to control the pressure of the gas-liquid mixing chamber.

[0014] To further optimize the technical solution, a B flow limiting valve is installed on the part of the gas injection pipe above the ground of the annulus side safety drainage system of an underground gas storage reservoir; the B flow limiting valve limits the medium flow rate in the gas injection pipe by changing the opening, and is used to control the gas-liquid flow ratio in the drainage pipe.

[0015] To further optimize the technical solution, a side wall of an air pressure chamber of an annulus-side safety drainage system of an underground gas storage reservoir is provided with a limiting device, and the limiting device is used to limit the bottom position of the piston in the air chamber.

[0016] Different from the traditional gas lift drainage method, this technical solution independently sets up gas injection pipes, drainage pipes and pulse drainage chambers in the annulus, isolating the gas lift drainage operation from the injection and production well column and the annulus without affecting the normal gas production operation of the injection and production well column.

[0017] About the gas lift drainage principle of the pulse drainage chamber:

[0018] In the initial state, there is no medium pressure in the gas injection pipe and the drainage pipe, and the piston of the gas-liquid mixing valve is in a closed state with respect to the gas injection pipe and the drainage pipe; due to the gas production pressure in the injection and production well column, the one-way valve is in a conducting state, and the bottom hole liquid enters the pulse drainage chamber from the one-way valve; when the drainage operation is performed, the ground air pressure pump station is turned on, and under the compressed gas pressure, the gas medium pushes the piston downward to enter the gas-liquid mixing chamber, and the pressure in the gas pressure chamber increases and the volume decreases; when the piston moves down to below the water inlet hole, the gas medium enters the pulse drainage chamber, and the one-way valve is closed under the pressure difference. Due to the difference in gas-liquid density, the gas medium enters the gas-liquid mixing chamber at the same time as the pulse drainage chamber, forming bubble liquid, which is discharged upward through the drainage pipe until the accumulated liquid in the pulse drainage chamber is completely drained. Finally, the air pressure pump station on the ground is closed, the air injection pipe loses pressure, and the piston is reset under the action of the air pressure chamber to close the air injection pipe and the drainage pipe. During the process of piston closing, the pressure in the pulse drainage chamber also decreases, and the one-way valve is opened under the pressure of the injection and production column. Once the bottom hole liquid is formed, it will enter the pulse drainage chamber again and wait for the next gas lift drainage operation to be discharged. The entire drainage process will not interfere with the normal gas production of the injection and production well column. The accumulated liquid is discharged independently from the drainage pipe and does not enter the gas pipeline, which does not increase the burden on the gas-liquid separator in the ground gas pipeline. Compared with the traditional gas lift drainage, multiple groups of gas lift valves are connected in series in the vertical direction of the column production well column, which is lower in cost, has no pressure medium in the annulus, and will not cause the safety risk of sealing failure.

[0019] Other technical effects of the present invention will be clearly described in the development of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a simplified schematic diagram of the structure of the present invention;

[0021] Figure 2 It is a simplified schematic diagram of the structure of the gas-liquid mixing valve before and after the piston moves downward;

[0022] Figure 3 This is a cross-sectional schematic diagram of the coaxial arrangement of the drainage pipe, cluster pipe, and gas injection pipe.

[0023] In the figure, 1. injection and production string; 2. annulus casing; 3. air pressure pump station; 4. drainage pipeline; 5. annulus; 6. packer; 7. air injection pipe; 8. drainage pipe; 9. pulse drainage chamber; 10. one-way valve; 11. gas-liquid mixing valve; 12. air chamber; 13. piston; 14. air pressure chamber; 15. gas-liquid mixing chamber; 16. water inlet hole; 17. cluster pipe; 18. A flow limiting valve; 19. B flow limiting valve; 20. limit device; 21. ground. DETAILED DESCRIPTION

[0024] like Figure 1 Example 1 shown:

[0025] A safe drainage system for the annulus side of an underground gas storage reservoir, comprising an injection and production pipe string 1, an annulus casing 2 located outside the injection and production pipe string 1, a gas pressure pump station 3 located on the ground, and a drainage pipeline 4 located on the ground; the space between the annulus casing 2 and the injection and production pipe string 1 is called an annulus 5; the bottom of the annulus 5 is sealed by a packer 6; and comprises:

[0026] An air injection pipe 7 and a liquid discharge pipe 8, wherein the upper end of the air injection pipe 7 is located above the ground and is connected to the air outlet of the air pressure pump station 3; the upper end of the liquid discharge pipe 8 is located above the ground and is connected to the water inlet of the drainage pipeline 4; the lower parts of both the air injection pipe 7 and the liquid discharge pipe 8 extend from the annulus 5 to the top of the packer 6;

[0027] The pulse drainage chamber 9 is arranged above the packer 6, at the bottom of the annulus 5, and is an annular chamber arranged outside the injection and production string 1. The pulse drainage chamber 9 is connected to the injection and production string through a one-way valve 10; the conduction direction of the one-way valve 10 is from the inner cavity of the injection and production string 1 to the pulse drainage chamber 9;

[0028] like Figure 2 As shown: a gas-liquid mixing valve 11 is arranged at the bottom of the pulse discharge chamber 9; the gas-liquid mixing valve 11 comprises an air chamber 12 and a piston 13 which slides and seals with the air chamber 12 in the air chamber 12; the lower ends of the gas injection pipe 7 and the discharge pipe 8 are both connected to the inner cavity of the air chamber 12; the upper end surface of the piston 13 is sealed with the lower ends of the gas injection pipe 7 and the discharge pipe 8; the piston 13 and the bottom of the air chamber 12 form a sealed air pressure chamber 14; the piston 13 and the upper part of the air chamber 12 form a gas-liquid mixing chamber 15; a water inlet hole 16 is arranged at the lower part of the side wall of the gas-liquid mixing chamber 15, when the air pressure pump station 3 pressurizes and supplies gas to the gas injection pipe 7, the air pressure pushes the piston 13 down to the water inlet hole 16, and at this time the water inlet hole 16 connects the gas-liquid mixing chamber 15 with the pulse discharge chamber 9.

[0029] Since the accumulated liquid at the bottom of the well enters the pulse drainage chamber 9 through the one-way valve 10, and the interior is filled with gas medium after the accumulated liquid is discharged from the pulse drainage chamber 9, the one-way valve 10 should be located at the upper part of the pulse drainage chamber 9, so that it is beneficial for the accumulated liquid to enter the pulse drainage chamber 9 from the one-way valve 10 and the gas medium to enter the injection and production well column from the one-way valve 10.

[0030] Since the accumulated liquid at the bottom of the well is discharged from the gas-liquid mixing valve 11 into the drainage pipe 8, during the process of the accumulated liquid being discharged, the gas medium also enters the pulse drainage chamber 9 from the water inlet hole 16 of the gas-liquid mixing valve 11. Therefore, the position of the gas-liquid mixing valve 11 should be set at the bottom of the pulse drainage chamber 9.

[0031] When the pulse discharge chamber 9 is filled with accumulated liquid, since the liquid cannot be compressed, the gas in the air pressure chamber 14 is required to compress and balance the pressure of the gas-liquid mixing chamber by the ground air pressure pump station 3. If there is no air pressure chamber 14, the ground air pressure pump station 3 cannot push the piston 13 open by pressurizing the air pipe 7.

[0032] The function of the “water inlet hole 16 ” is not only to allow the accumulated liquid to enter the gas-liquid mixing chamber 15 from the pulse drainage chamber 9 , but this process is also accompanied by the gas entering the pulse drainage chamber 9 from the water inlet hole 16 due to the difference in gas-liquid density.

[0033] To further optimize this embodiment, the gas injection pipe 7 and the liquid discharge pipe 8 of the annulus side safety liquid discharge system of the underground gas storage are coaxially arranged, and the gas injection pipe 7 is located inside the liquid discharge pipe 8. The gas injection pipe 7 and the liquid discharge pipe 8 are coaxially arranged, and the liquid discharge pipe 8 containing the bubble liquid will absorb the vibration of the gas injection pipe 7 when discharging liquid, and the construction is more convenient when it is laid in the annulus 5; the coaxial arrangement of the gas injection pipe 7 and the liquid discharge pipe 8 is also conducive to the force balance when the bottom ports of the two are sealed with the piston 13.

[0034] like Figure 3 As shown, this embodiment is further optimized, in an annular space between a drainage pipe 8 and a gas injection pipe 7 of a safety drainage system on the annular side of an underground gas storage reservoir, cluster pipes 17 are evenly distributed circumferentially, and the lower end of the cluster pipe 17 is connected to the lower port of the drainage pipe 8, and the upper end is connected to the ground outlet of the drainage pipe 8.

[0035] The principle of gas lift is to convert pure accumulated water into a mixture of bubbles. In the process of the bubble mixture being discharged upward, the liquid will flow back down along the pipe wall. The larger the pipe diameter, the smaller the surface ratio of the refluxed accumulated liquid mixed with the gas, and the lower the efficiency of the accumulated liquid discharge. The function of the cluster pipe 17 is to increase the reflux area of ​​the accumulated liquid in the gas injection pipe 7, reduce the amount of the accumulated liquid flowing back downward, and thus improve the efficiency of the accumulated liquid discharge.

[0036] To further optimize this embodiment, a portion of a drainage pipe 8 above the ground in a safety drainage system on the annulus side of an underground gas storage reservoir is installed with an A limiting valve 18; the A limiting valve 18 limits the flow rate of the medium in the drainage pipe 8 by changing the opening, so as to control the pressure of the gas-liquid mixing chamber.

[0037] A limiting valve 18 controls the flow rate of the medium in the discharge pipe 8, and can control the pressure of the gas-liquid mixing chamber. Under a fixed delivery pressure of the air pressure pump station 3, the greater the flow rate of the medium in the discharge pipe 8, the smaller the pressure of the gas-liquid mixing chamber; the smaller the flow rate of the medium in the discharge pipe 8, the greater the pressure of the gas-liquid mixing chamber; the pressure of the gas-liquid mixing chamber needs to push the piston 13 to be below the position of the water inlet, so that the accumulated liquid can enter the gas-liquid mixing chamber and be discharged. Therefore, A limiting valve 18 limits the flow rate of the medium in the discharge pipe 8, which can reduce the pressure of the air pressure pump station 3 and reduce energy consumption.

[0038] To further optimize this embodiment, a gas injection pipe 7 of a safe drainage system on the annulus side of an underground gas storage reservoir is provided with a B limiting valve 19 installed above the ground; the B limiting valve 19 limits the medium flow rate in the gas injection pipe 7 by changing the opening, and is used to control the gas-liquid flow ratio in the drainage pipe 8.

[0039] The greater the gas flow rate, the greater the power of the air pressure pump station 3, the higher the energy consumption, the smaller the relative density of the gas-liquid mixture in the discharge pipe 8, and the smaller the pressure of the gas-liquid mixture carried at the bottom of the discharge pipe 8 at the same height, the smaller the risk of pipeline leakage and rupture; conversely, the smaller the gas flow rate, the smaller the power of the air pressure pump station 3, the lower the energy consumption, the greater the relative density of the gas-liquid mixture in the discharge pipe 8, and the greater the pressure of the gas-liquid mixture carried at the bottom of the discharge pipe 8 at the same height, the greater the risk of pipeline leakage and rupture.

[0040] The A limiting valve 18 and the B limiting valve 19 work together to achieve a balance between pipeline safety, drainage efficiency, and power consumption of the air pressure pump station 3.

[0041] To further optimize this embodiment, a limit device is provided on the side wall of the air pressure chamber 14 of a safety drainage system on the annulus side of an underground gas storage reservoir, and the limit device is used to limit the bottom position of the piston 13 in the air chamber 12.

[0042] When the limiting valve 18 fails and becomes blocked, the pressure in the air pressure chamber 14 will increase. Adding a limit device can prevent the piston 13 from moving further downward, causing the pressure chamber to rupture and be damaged.

[0043] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0044] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. An annulus side drainage system for an underground gas storage reservoir, comprising an injection and production pipe string, an annulus casing located outside the injection and production pipe string, a gas pressure pump station located on the ground, and a drainage pipeline located on the ground; the space between the annulus casing and the injection and production pipe string is called an annulus; the bottom of the annulus is sealed by a packer; characterized in that, include: An air injection pipe and a liquid discharge pipe, wherein the upper end of the air injection pipe is located above the ground and is connected to the air outlet of the air pressure pump station; the upper end of the liquid discharge pipe is located above the ground and is connected to the water inlet of the drainage pipeline; the lower parts of both the air injection pipe and the liquid discharge pipe extend from the annulus to the top of the packer; A pulse drainage chamber, which is arranged above the packer and at the bottom of the annulus, and is an annular chamber arranged outside the injection and production string. The pulse drainage chamber is connected to the injection and production string through a one-way valve; the conduction direction of the one-way valve is from the inner cavity of the injection and production string to the pulse drainage chamber; A gas-liquid mixing valve is arranged at the bottom of the pulse liquid discharge chamber; the gas-liquid mixing valve comprises an air chamber, and a piston which is slidably sealed with the air chamber in the air chamber; the lower ends of the gas injection pipe and the liquid discharge pipe are both in communication with the inner cavity of the air chamber; the upper end surface of the piston is sealed with the lower ends of the gas injection pipe and the liquid discharge pipe; the piston and the bottom of the air chamber form a sealed air pressure chamber; the piston and the upper part of the air chamber form a gas-liquid mixing chamber; a water inlet hole is arranged at the lower part of the side wall of the gas-liquid mixing chamber, and when the air pressure pump station pressurizes and transmits gas to the gas injection pipe, the air pressure pushes the piston down to the water inlet hole, and at this time the water inlet hole connects the gas-liquid mixing chamber with the pulse liquid discharge chamber; The gas injection pipe is coaxially arranged with the drainage pipe, and the gas injection pipe is located inside the drainage pipe; cluster pipes are evenly distributed circumferentially in the annular space between the drainage pipe and the gas injection pipe, and the lower end of the cluster pipe is connected to the lower port of the drainage pipe, and the upper end is connected to the ground outlet of the drainage pipe.

2. The annulus side drainage system of an underground gas storage according to claim 1, characterized in that : The portion of the drainage pipe above the ground is installed with a flow limiting valve A; the flow limiting valve A limits the flow rate of the medium in the drainage pipe by changing the opening, and is used to control the pressure of the gas-liquid mixing chamber.

3. The annulus side drainage system of an underground gas storage according to claim 1, characterized in that : A B flow limiting valve is installed on the part of the gas injection pipe above the ground; the B flow limiting valve limits the flow rate of the medium in the gas injection pipe by changing the opening, and is used to control the gas-liquid flow ratio in the discharge pipe.

4. The annulus side drainage system of an underground gas storage according to claim 1, characterized in that : The side wall of the air pressure chamber is provided with a limiting device, and the limiting device is used to limit the bottom position of the piston in the air chamber.

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