Shale gas well gas lift liquid drainage system, liquid drainage method and gas production method

Abstract

The invention belongs to the field of natural gas drainage and gas recovery, and particularly relates to a shale gas well gas lift liquid drainage system, a liquid drainage method and a gas recovery method. The shale gas well gas lift liquid drainage system comprises an underground part, the underground part comprises a sleeve, a first oil pipe arranged in the sleeve and a second oil pipe arranged in the first oil pipe, and a check valve is arranged at the end, away from a wellhead, of the first oil pipe; the gas production tree is arranged at a wellhead and is connected with the first oil pipe, the second oil pipe and the casing pipe; the pressurizing gas lift equipment injects gas into a first annulus between the casing pipe and the first oil pipe and a second annulus between the first oil pipe and the second oil pipe through a gas production tree; wherein the flow direction of the check valve faces a wellhead. When the liquid level in a shaft is low, effective gas lifting can still be achieved.

Description

Technical Field

[0001] This invention belongs to the field of natural gas drainage and gas production, specifically relating to a shale gas well gas lift drainage system, drainage method, and gas production method. Background Technology

[0002] Wellbore fluid accumulation is a key factor restricting the full release of shale gas well production capacity. Removing wellbore fluid can reduce bottomhole back pressure, improve well production efficiency, and promote long-term stable shale gas production. Drainage and gas production technologies such as plunger gas lift, bubble drainage, and gas lift are effective means to eliminate the impact of wellbore fluid accumulation in the later stages of shale gas production. However, because the produced fluid in shale gas wells is mainly fracturing fluid, the fluid supply faces uncertainty. Furthermore, shale gas wells have long horizontal sections, typically 1500–3000m, and various structures such as updip, downdip, and serpentine. These unique characteristics greatly limit the application of various drainage and gas production technologies in shale gas wells. Currently, gas lift technology is the drainage aid technology with the widest adaptability to different production ranges, the deepest lift, good drainage effect, and long effective time. It has been widely used in shale gas extraction and will continue to be so. Research on gas lift technology is of great significance for the stable production of shale gas.

[0003] Chinese patent application CN117307103A discloses an automatic gas lift drainage system and method for high-yield water wells, including a downhole section comprising a casing and tubing disposed within the casing, with a casing-tubing connection point at the lower part of the tubing and the casing; a gas tree located at the wellhead and connected to the tubing and the casing; and a gas-liquid mixing injection device connected to the gas tree, which injects a gas-liquid mixture into the annulus of the casing and tubing through the gas tree; wherein the gas-liquid mixture in the annulus enters the tubing through the casing-tubing connection point, reducing the liquid column density within the tubing, thereby achieving continuous drainage. This invention utilizes the liquid column pressure to increase the injection channel pressure, thereby reducing the surface gas lift start-up pressure and lowering equipment investment.

[0004] However, when the liquid level inside the wellbore is low, this system and method cannot achieve effective gas lift.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a shale gas well gas lift drainage system, drainage method and gas production method. The present invention can still achieve effective gas lift when the liquid level in the wellbore is low.

[0007] This invention includes the following technical solutions:

[0008] The first aspect of this invention provides a shale gas well gas lift fluid removal system, comprising,

[0009] The downhole portion includes a casing, a first tubing disposed within the casing, and a second tubing disposed within the first tubing. A check valve is provided at the end of the first tubing away from the wellhead.

[0010] A gas production tree is installed at the wellhead and connected to the first tubing, the second tubing, and the casing.

[0011] A booster gas lift device, wherein the booster gas lift device injects gas into the first annulus between the casing and the first tubing and the second annulus between the first tubing and the second tubing through the gas production tree;

[0012] The flow direction of the single-flow valve is towards the wellhead.

[0013] Furthermore, it also includes a gas-liquid separator, which is connected to the outlet of the gas harvesting tree, and the gas outlet of the gas-liquid separator is connected to the booster gas lift device.

[0014] Furthermore, the inlet of the pressurized gas lift device draws gas through a gas sampling tree.

[0015] Furthermore, the gas production tree includes a first gas injection pipe, a second gas injection pipe, a first gas production pipe, and a second gas production pipe. Each of the first gas injection pipe, the second gas injection pipe, the first gas production pipe, and the second gas production pipe is equipped with a valve. One end of each of the first and second gas injection pipes is connected to the outlet of the booster gas lift device. The other end of the first gas injection pipe is connected to a first annulus, and the other end of the second gas injection pipe is connected to a second annulus. One end of each of the first and second gas production pipes is connected to the inlet of the booster gas lift device. The other end of the first gas production pipe is connected to the second annulus, and the other end of the second gas production pipe is connected to the second oil pipe.

[0016] Furthermore, it also includes a three-way valve, the inlet of which is connected to the outlet of the booster air lift device, and the two outlets of which are respectively connected to the first annulus and the second annulus.

[0017] Furthermore, it also includes a controller connected to the three-way valve.

[0018] Furthermore, the pressurized airlift device is a compressor.

[0019] A second aspect of the present invention provides a gas lift fluid removal method for low-pressure horizontal wells in shale formations, comprising the aforementioned gas lift fluid removal system for shale gas wells, wherein the gas lift fluid removal method is as follows:

[0020] Obtain the pressure value P of the first oil pipe t ;

[0021] If Pt >P tmax The pressurized airlift device injects air into the second annulus until P t <P tmin The pressurized airlift device stops injecting air into the second annulus;

[0022] Among them, P tmax P is the maximum pressure threshold of the first oil pipe. tmin This is the minimum pressure threshold for the first oil pipe.

[0023] Furthermore, the drainage method includes the following steps:

[0024] Obtain the pressure value P of the casing. c ;

[0025] If P t <P tmin And P c >P cmax The pressurized airlift device injects air into the first annulus until P t >P tmin The pressurized airlift device stops injecting air into the first annular ring and starts injecting air into the second annular ring until P... t <P tmin The pressurized airlift device stops injecting air into the second annulus;

[0026] Among them, P cmax This is the maximum pressure threshold for the casing.

[0027] A third aspect of the present invention provides a gas production method, including the shale gas well gas lift and fluid removal system described above, the gas production method comprising the following steps:

[0028] Gas is extracted using the power provided by the aforementioned pressurized gas lift device;

[0029] When P t >P tmax The pressurized airlift device injects air into the second annulus until P t <P tmin The pressurized airlift device stops injecting air into the second annulus; when P t <P tmin And P c >P cmax The pressurized airlift device injects air into the first annulus until P t >P tmin The pressurized airlift device stops injecting air into the first annular ring and starts injecting air into the second annular ring, directly P t <P tmin The pressurized airlift device stops injecting air into the second annulus.

[0030] By adopting the above technical solution, the present invention has the following advantages:

[0031] 1. The drainage system of the present invention can still achieve effective gas lift when the liquid level in the wellbore is low.

[0032] 2. This invention solves the problem of low liquid level in the wellbore and inability to effectively lift gas without the need for a packer.

[0033] 3. This invention improves the management level of shale gas well gas lift process by setting up a controller to control gas lift and gas production.

[0034] 4. This invention significantly improves the efficiency of gas lift and liquid lifting, as well as the level of process management, which is conducive to the long-term stable production of gas wells, while reducing the waste of human, material and other resources.

[0035] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of a shale gas well gas lift fluid discharge system according to an embodiment of the present invention. Figure 1 ;

[0038] Figure 2 This is a schematic diagram of the structure of a shale gas well gas lift fluid discharge system according to an embodiment of the present invention. Figure 2 ;

[0039] Figure 3 This is a schematic diagram of the structure of a shale gas well gas lift fluid discharge system according to an embodiment of the present invention. Figure 3 ;

[0040] Figure 4 This is a schematic diagram of the structure of a shale gas well gas lift fluid discharge system in an embodiment of the present invention;

[0041] In the diagram: 10-casing, 20-first tubing, 30-second tubing, 40-check valve, 50-first annulus, 60-second annulus, 70-growth tree, 71-first injection pipeline, 72-second injection pipeline, 73-first gas production pipeline, 74-second gas production pipeline, 80-boost gas lift device, 90-three-way valve, 100-gas-liquid separator. Detailed Implementation

[0042] The following description provides many different embodiments or examples for implementing various features of the invention. The elements and arrangements described in the specific examples below are only for concise expression of the invention and are merely examples, not intended to limit the invention.

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0044] In existing technologies, if only one tubing is installed, effective gas lift cannot be achieved when the downhole fluid level is low, severely affecting gas production efficiency. The first aspect of this embodiment provides a shale gas well gas lift and fluid removal system, such as... Figure 1 As shown, including,

[0045] The downhole portion includes a casing 10, a first tubing 20 disposed within the casing 10, and a second tubing 30 disposed within the first tubing 20. A check valve 40 is provided at the end of the first tubing 20 away from the wellhead.

[0046] A gas production tree 70 is installed at the wellhead and connected to the first tubing 20, the second tubing 30, and the casing 10.

[0047] The booster gas lift device 80 injects gas into the first annulus 50 between the casing 10 and the first oil pipe 20 and the second annulus 60 between the first oil pipe 20 and the second oil pipe 30 through the gas tree 70; it should be noted that the booster gas lift device 80 is a device capable of providing high-pressure gas.

[0048] The flow direction of the one-way valve 40 is towards the wellhead. The one-way valve 40 can be a check valve or a one-way valve 40 composed of a ball seat and a valve ball.

[0049] The structure of this invention is applicable to gas lift drainage in various wells, especially horizontal wells; compared to vertical wells, in horizontal wells, such as... Figure 2 As shown, since the gas-liquid surface is horizontal, even when there is a lot of liquid inside, the liquid level will not be very high. However, this accumulated liquid seriously affects the full release of shale gas well production capacity, so it is necessary to drain the accumulated liquid. However, due to the low liquid level inside the wellbore, the existing single tubing structure is ineffective in achieving effective gas lift. This invention, by setting a first tubing 20, a second tubing 30, and a check valve 40, can achieve effective gas lift at low liquid levels, ensuring the full release of shale gas well production capacity and improving the gas well production rate.

[0050] When liquid is discharged by gas lift, gas is also mixed in. Therefore, in some embodiments, a gas-liquid separator 100 is also included. The gas-liquid separator 100 is connected to the outlet of the gas production tree 70, and the gas outlet of the gas-liquid separator 100 is connected to the booster gas lift device 80. The gas separated by the gas-liquid separator 100 can also be used in the gas well after entering the booster gas well equipment. During the gas production process, gas-liquid separation and collection are achieved through the gas-liquid separator 100.

[0051] The gas lift drainage system of the present invention can be used solely for gas lift drainage. However, if it is used solely for gas lift drainage, a gas production system still needs to be set up at the wellhead, which not only increases the cost but also increases the complexity of arranging the system at the wellhead. Therefore, in some embodiments, the inlet of the pressurized gas lift device 80 is gas produced through the gas production tree 70.

[0052] In some embodiments, such as Figure 1 As shown, the gas extraction tree 70 includes a first gas injection pipe 71, a second gas injection pipe 72, a first gas extraction pipe 73, and a second gas extraction pipe 74. Each of the first gas injection pipe 71, second gas injection pipe 72, first gas extraction pipe 73, and second gas extraction pipe 74 is equipped with a valve. One end of the first gas injection pipe 71 and the second gas injection pipe 72 are connected to the outlet of the booster gas lift device 80. The other end of the first gas injection pipe 71 is connected to the first annulus 50, and the other end of the second gas injection pipe 72 is connected to the second annulus 60. One end of the first gas extraction pipe 73 and the second gas extraction pipe 74 are connected to the inlet of the booster gas lift device 80. The other end of the first gas extraction pipe 73 is connected to the second annulus 60, and the other end of the second gas extraction pipe 74 is connected to the second oil pipe 30. This structure enables simultaneous gas extraction and gas lift. The valves can be manual valves or solenoid valves, and can be controlled by a controller.

[0053] Both the first annulus 50 and the second annulus 60 require gas injection from the booster air lift device 80. Specifically, this can be achieved by connecting both the first annulus 50 and the second annulus 60 to a single booster air lift device 80, but this increases costs. Alternatively, a single booster air lift device 80 can be used to inject gas into both the first annulus 50 and the second annulus 60. In this method, two valves can be used to control the gas injection pathways to the first annulus 50 and the second annulus 60 respectively. Therefore, in some embodiments, such as... Figure 1 As shown, it also includes a three-way valve 90. The inlet of the three-way valve 90 is connected to the outlet of the booster air lift device 80, and the two outlets of the three-way valve 90 are respectively connected to the first annulus 50 and the second annulus 60. The three-way valve 90 controls whether the booster air lift device 80 injects air into the first annulus 50 or the second annulus 60, offering advantages in equipment simplification and ease of control.

[0054] In some embodiments, a controller is also included, connected to the three-way valve 90, to achieve automatic control of the three-way valve 90. Simultaneously, a control method can be preset within the controller, which adjusts the control based on the acquired pressure value P of the first oil pipe 20. t and the pressure value P of the sleeve 10 c Make a judgment; if P t >P tmax The controller controls the three-way valve 90 to inject air into the second annulus 60 through the pressurized airlift device 80 until P t <P tmin The controller controls the three-way valve 90 to stop the pressurized airlift device 80 from injecting air into the second annulus 60; if P t <P tmin And P c >P cmax The controller controls the three-way valve 90 to inject air into the first annulus 50 through the pressurized airlift device 80 until P t >P tmin The pressurized airlift device 80 stops injecting air into the first annulus 50 and injects air into the second annulus 60 until P... t <P tmin The controller controls the three-way valve 90 to stop the pressurized airlift device 80 from injecting air into the second annulus 60; wherein, P tmax P is the maximum pressure threshold of the first oil pipe 20. tmin P is the minimum pressure threshold of the first oil pipe 20; cmax This is the maximum pressure threshold of casing 10. This allows for air lift control via the controller.

[0055] Pressure value P of first oil pipe 20 t Pressure value P of casing 10c The maximum pressure threshold P of the first oil pipe 20 can be obtained in real time by setting a pressure sensor. tmax The minimum pressure threshold P of the first oil pipe 20 tmin The maximum pressure threshold P of casing 10 cmax This can be obtained by those skilled in the art based on experience.

[0056] In some embodiments, the pressurized gas lift device 80 is a compressor. The compressor can simultaneously meet the requirements of wellhead depressurization and gas lift.

[0057] The second aspect of this embodiment provides a gas lift fluid removal method for low-pressure horizontal wells in shale gas, including the gas lift fluid removal system for shale gas wells described above, wherein the gas lift fluid removal method is as follows:

[0058] Obtain the pressure value P of the first oil pipe 20 t ;

[0059] like Figure 2 As shown, if P t >P tmax The pressurized airlift device 80 injects air into the second annulus 60 until P t <P tmin The pressurized air lift device 80 stops injecting air into the second annulus 60;

[0060] Among them, P tmax P is the maximum pressure threshold of the first oil pipe 20. tmin This is the minimum pressure threshold for the first oil pipe 20.

[0061] The method of this invention can achieve effective gas lift at low liquid levels, avoid liquid accumulation that prevents shale gas production capacity from being fully released, and improve the production rate of gas wells.

[0062] It should be noted that the principle of achieving effective air lift at low liquid levels is that, through the cooperation of the first oil pipe 20 and the second oil pipe 30, the air lift channel (i.e., the second annulus 60) is made smaller, and the channel for air lift to discharge liquid is also smaller (i.e., the second oil pipe 30), thus requiring less air lift force.

[0063] In this invention, the air-lift fluid discharge is all discharged through the second oil pipe 20. If there is a large amount of fluid accumulated in the casing 10 (i.e., P...), c >P cmax When the fluid accumulation in the first oil pipe 20 is relatively small (i.e., P), t <P tmin First, air can be injected into the first annulus 50 to allow the accumulated fluid in the casing 10 to enter the second annulus 60 and / or the second oil pipe 30; therefore, in some embodiments, the drainage method includes the following steps:

[0064] Obtain the pressure value P of the sleeve 10 c ;

[0065] like Figure 3 As shown, if P t <P tmin And P c >P cmax The pressurized airlift device 80 injects air into the first annulus 50 until P t >P tmin The pressurized air lift device 80 stops injecting air into the first annulus 50, such as Figure 4 As shown, gas is injected into the second annulus at 60° until P... t <P tmin The pressurized air lift device 80 stops injecting air into the second annulus 60;

[0066] Among them, P cmax This is the maximum pressure threshold of casing 10.

[0067] The third aspect of this embodiment provides a gas production method, including the shale gas well gas lift fluid removal system described above, the gas production method comprising the following steps:

[0068] Gas is extracted using the power provided by the booster gas lift device 80; if the booster gas lift device 80 is a compressor, it can provide a pressure differential during operation, causing the gas in the well to flow towards the wellhead, thereby realizing gas extraction.

[0069] The gas extraction method of the present invention can achieve simultaneous gas lift and gas extraction. During the gas extraction process, when P t >P tmax The pressurized airlift device 80 injects air into the second annulus 60 until P t <P tmin The pressurized air lift device 80 stops injecting air into the second annulus 60; when P t <P tmin And P c >P cmax The pressurized airlift device 80 injects air into the first annulus 50 until P t >P tmin The pressurized airlift device 80 stops injecting air into the first annulus 50 and injects air into the second annulus 60 until P... t <P tmin The pressurized gas lift device 80 stops injecting gas into the second annulus 60. Furthermore, since gas well and gas production occur simultaneously, the pressure difference provided by the pressurized gas lift device 80 during gas production also assists in gas lift, improving gas lift efficiency.

[0070] Because gas extraction is not stopped during the gas lift process, the gas extraction method of this invention has the advantage of high gas extraction efficiency. It should be noted that stopping gas extraction during the gas lift process should also be within the protection scope of the gas lift liquid discharge method of this invention.

[0071] It should be noted that after entering the booster air lift equipment, the gas is used for injection, and the rest is collected and stored.

[0072] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0073] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of multiple components or the interaction between multiple components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0074] In the description of this invention, it should be understood that all terms used to indicate orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as a limitation of this invention.

[0075] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A shale gas well gas lift fluid removal system, characterized in that, include, The downhole portion includes a casing (10), a first tubing (20) disposed within the casing (10), and a second tubing (30) disposed within the first tubing (20). A check valve (40) is provided at the end of the first tubing (20) away from the wellhead. A gas production tree (70) is installed at the wellhead and connected to the first tubing (20), the second tubing (30), and the casing (10); A booster gas lift device (80) injects gas into the first annulus (50) between the casing (10) and the first tubing (20) and the second annulus (60) between the first tubing (20) and the second tubing (30) through a gas tree (70); The flow direction of the single-flow valve (40) is towards the wellhead.

2. The shale gas well gas lift fluid removal system according to claim 1, characterized in that, It also includes a gas-liquid separator (100), which is connected to the outlet of the gas harvesting tree (70), and the gas outlet of the gas-liquid separator (100) is connected to the booster gas lift device (80).

3. A shale gas well gas lift fluid removal system according to claim 1 or 2, characterized in that, The inlet of the pressurized gas lift device (80) collects gas through the gas collection tree (70).

4. A shale gas well gas lift fluid removal system according to claim 3, characterized in that, The gas tree (70) includes a first gas injection pipe (71), a second gas injection pipe (72), a first gas extraction pipe (73), and a second gas extraction pipe (74). Each of the first gas injection pipe (71), the second gas injection pipe (72), the first gas extraction pipe (73), and the second gas extraction pipe (74) is equipped with a valve. One end of the first gas injection pipe (71) and the second gas injection pipe (72) are connected to the outlet of the booster gas lift device (80). The other end of the first gas injection pipe (71) is connected to the first annulus (50), and the other end of the second gas injection pipe (72) is connected to the second annulus (60). One end of the first gas extraction pipe (73) and the second gas extraction pipe (74) are connected to the inlet of the booster gas lift device (80). The other end of the first gas extraction pipe (73) is connected to the second annulus (60), and the other end of the second gas extraction pipe (74) is connected to the second oil pipe (30).

5. A shale gas well gas lift fluid removal system according to claim 3, characterized in that, It also includes a three-way valve (90), the inlet of which is connected to the outlet of the booster air lift device (80), and the two outlets of which are connected to the first annulus (50) and the second annulus (60) respectively.

6. A shale gas well gas lift fluid removal system according to claim 5, characterized in that, It also includes a controller connected to the three-way valve (90).

7. A shale gas well gas lift fluid removal system according to claim 1, characterized in that, The booster air lift device (80) is a compressor.

8. A gas lift fluid removal method for low-pressure horizontal wells in shale formations, characterized in that, Including a shale gas well gas lift fluid removal system as described in any one of claims 1-7, wherein the gas lift fluid removal method is as follows: Obtain the pressure value P of the first oil pipe (20) t ; If P t >P tmax The pressurized airlift device (80) injects air into the second annulus (60) until P t <P tmin The pressurized air lift device (80) stops injecting air into the second annulus (60); Among them, P tmax P is the maximum pressure threshold of the first oil pipe (20). tmin The minimum pressure threshold of the first oil pipe (20) is given.

9. A gas lift fluid removal method for low-pressure horizontal wells in shale formations according to claim 8, characterized in that, The drainage method includes the following steps: Obtain the pressure value P of the sleeve (10). c ; If P t <P tmin And P c >P cmax The pressurized airlift device (80) injects air into the first annulus (50) until P t >P tmin The pressurized airlift device (80) stops injecting air into the first annulus (50) and injects air into the second annulus (60) until P t <P tmin The pressurized air lift device (80) stops injecting air into the second annulus (60); Among them, P cmax The maximum pressure threshold of the casing (10) is given.

10. A gas extraction method, characterized in that, Including a shale gas well gas lift fluid removal system as described in any one of claims 3-7, the gas production method includes the following steps: Gas is extracted using the power provided by the pressurized gas lift device (80); When P t >P tmax The pressurized airlift device (80) injects air into the second annulus (60) until P t <P tmin The pressurized airlift device (80) stops injecting air into the second annulus (60); when P t <P tmin And P c >P cmax The pressurized airlift device (80) injects air into the first annulus (50) until P t >P tmin The pressurized airlift device (80) stops injecting air into the first annulus (50) and injects air into the second annulus (60) until P t <P tmin The pressurized air lift device (80) stops injecting air into the second annulus (60).

Images