Casing gas recovery device and tubular column and use method thereof

Abstract

The invention discloses a casing gas recovery device and a pipe column and a using method thereof. The casing gas recovery device comprises a plunger pipe and an outer cylinder, the plunger pipe is arranged in the outer cylinder and is divided into a large plunger and a small plunger, the small plunger is sleeved with the large plunger, a small plunger sealing seat is arranged on the inner wall of the outer cylinder, and the small plunger is inserted into the small plunger sealing seat; an air cavity is formed among the outer cylinder, the small plunger sealing seat and the large plunger, and the outer cylinder is provided with an air inlet assembly in the air cavity; the large plunger is provided with an air outlet unit. The self-weight load of the oil well rod column is used for compressing gas, extra energy is not needed, and more energy is saved; casing gas is collected in a compression mode, the pressure in the casing is not affected by return pressure, and the casing pressure can be reduced to be lower than the return pressure; the casing gas is recycled underground, and the problem of freezing and blocking in winter when the casing gas is collected on the ground is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield gas recovery, and particularly to a casing gas recovery device, its string, and a usage method thereof. Background Art

[0002] Oilfield casing associated gas coexists with crude oil, and is a combustible gas rich in crude oil, which is produced simultaneously with the crude oil. During the production process of the oil well, when the bottom hole pressure is lower than the saturation pressure of the crude oil, natural gas is separated from the crude oil. A part of the separated natural gas is produced along with the liquid flow into the pump chamber of the sucker rod pump, and a part enters the annulus between the casing and the tubing to form casing gas, forming a gas column with a certain pressure in the upper part. In actual production, in order to prevent the casing pressure from being too high and causing the submergence depth of the sucker rod pump to be too low, it is necessary to regularly release the casing gas to reduce the impact of the gas on the sucker rod pump, so that the sucker rod pump maintains a certain submergence depth and production pressure difference, thereby achieving the purpose of improving the pump efficiency and increasing the production. At that time, without strict external gas supply tasks and without the conditions for natural gas storage, producing by releasing the casing gas in high gas-oil ratio wells was a feasible means for tapping the potential and increasing the efficiency of oil wells. However, with the increasing emphasis on natural gas production in oilfields and the enhancement of environmental protection awareness, the losses and hazards of discharging casing gas have gradually emerged.

[0003] Since oil well associated gas often contains harmful non-hydrocarbon compounds such as water, carbon monoxide, hydrogen sulfide, nitrogen, helium, and mechanical impurities in addition to light hydrocarbons, it is very difficult to treat at the wellhead. Previously, oil associated gas was usually flared, and the emitted oil and gas polluted the local natural environment. After realizing the damage to the environment caused by flaring associated gas on the spot, enterprises at all levels have adopted the method of discharging after combustion for gases with large emissions. However, the CO2, CO, sulfides, etc. generated after combustion not only pollute the atmosphere, but more importantly, waste non-renewable clean resources, forming a vicious cycle. Recycling this part of the casing gas can not only reduce environmental pollution, but also effectively utilize this part of the casing gas to achieve the effect of energy conservation. Therefore, considering the long-term development of oilfields, comprehensively recycling and utilizing associated gas is the best choice to achieve the goals of harmonious development between humans and nature and sustainable development of enterprises.

[0004] Currently, the relatively commonly used casing gas recovery devices in China mainly include constant pressure type casing gas recovery devices, pressurized type casing gas recovery devices, etc. The constant pressure type casing gas recovery device is also called a constant pressure gas release valve, which is equivalent to installing a safety valve on the oil well casing. The opening pressure is adjusted according to the back pressure of the oil well. When the pressure of the overflowing casing gas accumulating in the annulus exceeds the set value, it is discharged into the single-well gathering and transportation pipeline and transported to the treatment station, avoiding environmental pollution and resource waste caused by flaring. The constant pressure gas release valve has the advantages of simple structure and convenient maintenance. The pressurized type casing gas recovery device uses a compressor to compress the casing gas in the casing and then injects it into the production process. Compared with the constant pressure type casing gas recovery device, this method can reduce the casing pressure to a lower pressure.

[0005] Both of these two common casing gas recovery methods have their application limitations. Due to a certain backpressure in the production process, the constant-pressure casing gas recovery device only works when the pressure in the casing is greater than the backpressure, resulting in a certain pressure always remaining in the casing; while the pressurized casing gas recovery device has a large investment cost, complex management and maintenance, and high energy consumption.

[0006] Publication (Announcement) Number: CN215108858U discloses a casing gas recovery system for low-liquid-volume oil wells. The system includes a jet recovery device, and also has a liquid inlet pipe, a liquid stabilizer, a booster pump, a gas-liquid stabilizer, and a gas collection pipeline. The gas-liquid stabilizer is connected to the upper end of the jet recovery device; one pipe orifice of the liquid inlet pipe is connected to the liquid inlet of the liquid stabilizer and is successively connected to the pump unit control valve, the booster pump, the liquid discharge pipeline, and the gas-liquid stabilizer through the liquid outlet of the liquid stabilizer; the exhaust port of the liquid stabilizer is connected to the gas-liquid stabilizer through a gas collection pipeline, a four-way joint, and a pressure stabilizing pipeline in sequence; the negative pressure chamber of the jet recovery device is connected to the casing valve through a check valve and a pipeline; the two interfaces on both sides of the four-way joint are respectively connected to the diffuser pipe of the jet recovery device and the sampling valve.

[0007] This prior art is a pressurized casing gas recovery device, which has problems of large investment cost, complex management and maintenance, and high energy consumption.

[0008] Publication (Announcement) Number: CN213018870U discloses an associated gas recovery device for a well group, belonging to oilfield production supporting equipment. The associated gas recovery system includes a compression cylinder, an inlet gas pipeline, an outlet gas pipeline, a buffer tank, and a parallel gas pipeline. Among them: the parallel gas pipeline collects the associated gas in multiple oil production wells through the casing and stores the associated gas in the buffer tank. The inlet of the compression cylinder is connected to the buffer tank through the inlet gas pipeline, and the outlet of the compression cylinder is connected to the well group oil pipeline through the outlet gas pipeline to pressurize and recover the associated gas.

[0009] This prior art is a pressurized casing gas recovery device, which has problems of large investment cost, complex management and maintenance, and high energy consumption.

[0010] Publication (Announcement) Number: CN116838291A discloses a casing gas pressure reduction and recovery device, which relates to the technical field of oil well casing gas recovery. It includes a base, above which an oil well casing is arranged, and the oil well casing is fixedly embedded in the upper surface of the base. The top of the oil well casing is fixedly connected to two oil outlet pipes, and a sucker rod is installed inside the oil well casing. Through the cooperative setting among the base, the oil well casing, the oil outlet pipes, the sucker rod, the gas outlet pipe, the cylinder housing, the casing gas recovery assembly, the air intake assembly and the exhaust assembly, the pumping unit drives the sucker rod to move upward. By using the casing gas recovery assembly, the casing gas can enter the inside of the cylinder housing through the air intake assembly. The pumping unit drives the sucker rod to move downward, so that the casing gas is discharged into the inside of the oil outlet pipe through the exhaust assembly for recovery. It can prevent the casing gas from causing too low a filling coefficient of the oil pump and avoid gas locking of the oil pump, and can ensure the liquid production of the oil well.

[0011] This prior art uses the movement of the sucker rod as the driving force for the casing gas recovery device, but there are problems such as occupying the wellhead space and affecting the installation of other wellhead equipment, and there is also the problem of easy freezing and blocking in winter.

[0012] In summary, the technical solutions, the technical problems to be solved and the beneficial effects of the above-disclosed technologies are all different from those of the present invention. For more technical features, technical problems to be solved and beneficial effects of the present invention, there is no technical inspiration in the above-disclosed technical documents. Summary of the Invention

[0013] Aiming at the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a casing gas recovery device, its pipe string and usage method to achieve the effective collection and utilization of casing gas.

[0014] To achieve the above purpose, the present invention adopts the following technical solutions:

[0015] A casing gas recovery device includes a plunger pipe and an outer cylinder. The plunger pipe is arranged in the outer cylinder. The plunger pipe is divided into a large plunger and a small plunger. The large plunger is sleeved on the small plunger. A small plunger seal seat is arranged on the inner wall of the outer cylinder, and the small plunger is inserted into the small plunger seal seat. An air cavity is formed among the outer cylinder, the small plunger seal seat and the large plunger. An air intake assembly is arranged on the outer cylinder in the air cavity area. The large plunger is provided with an air outlet unit.

[0016] Further, an air intake port is arranged on the outer cylinder in the air cavity area. The air intake assembly is arranged on the outer wall of the outer cylinder and is connected to the air intake port.

[0017] Specifically, the air intake assembly includes an air intake assembly housing and an air intake port bottom pipe.

[0018] Specifically, a first air intake channel is arranged at the center of the air intake port bottom pipe.

[0019] Specifically, the housing of the intake assembly is provided with a second intake passage axially penetrating therethrough, and the bottom pipe of the intake port is connected to the lower end of the second intake passage;

[0020] Specifically, in the second intake passage, a first boss is provided above the bottom pipe of the intake port, and an intake valve seat is provided between the bottom pipe of the intake port and the first boss;

[0021] Specifically, an intake valve is installed above the intake valve seat, an intake return spring is installed above the intake valve, and an intake port gland is provided at the upper end of the housing of the intake assembly, so that the intake return spring is in a compressed state;

[0022] Specifically, the intake return spring presses the intake port gland upward and the intake valve downward, so that the intake valve sits on the intake valve seat;

[0023] Specifically, the housing of the intake assembly is provided with a third intake passage above the intake valve seat, connecting the air chamber and the second intake passage.

[0024] Further, between the intake valve seat and the inner wall of the second intake passage, and between the intake port gland and the housing of the intake assembly, they are sealed by intake seals.

[0025] Further, the outlet unit includes an outlet passage and a bottom pipe of the outlet port;

[0026] Specifically, the bottom pipe of the outlet port is arranged at the lower end of the outlet passage, and the outlet passage is connected to the air chamber through the bottom pipe of the outlet port;

[0027] Specifically, a second boss is provided above the bottom pipe of the outlet port, and an outlet valve seat is provided between the bottom pipe of the outlet port and the second boss;

[0028] Specifically, an outlet valve is provided above the outlet valve seat, an outlet return spring is provided above the outlet valve, and an outlet port gland is provided on the outlet passage, so that the outlet return spring is in a compressed state;

[0029] Specifically, the outlet return spring presses the outlet port gland upward and the outlet valve downward, so that the outlet valve sits in the outlet valve seat;

[0030] Specifically, the outlet port gland is provided with air outlet holes, connecting the outlet passage with the upper part.

[0031] Further, between the outlet port gland and the large plunger, and between the outlet valve seat and the outlet passage, they are sealed by outlet seals;

[0032] Specifically, at least two outlet units are provided and are evenly arranged circumferentially around the large plunger;

[0033] Specifically, all the gland covers of the air outlets in the at least two air outlet units are integrally formed and connected to the large plunger through threads.

[0034] Furthermore, the small plunger has a hollow structure, and an oil flow channel for crude oil is formed in the center.

[0035] Specifically, an oil outlet is arranged at the upper end of the small plunger, and an oil inlet is arranged at the lower end; the length of the small plunger is greater than the production stroke of the oil pump.

[0036] Specifically, at least two large plunger seals are arranged between the large plunger and the outer cylinder, and the large plunger seals are rigid sealing rings or soft seals.

[0037] Specifically, at least two small plunger seals are arranged between the small plunger seal seat and the small plunger, and the small plunger seals are rigid sealing rings or soft seals.

[0038] Specifically, tubing collars are arranged at both the upper and lower ends of the outer cylinder.

[0039] Specifically, a sucker rod collar is arranged at the upper end of the small plunger for connecting with the upper sucker rod, and a sucker rod thread is arranged at the lower end of the small plunger for connecting with the lower sucker rod.

[0040] Specifically, the large plunger and the small plunger are integrally manufactured or connected through threads.

[0041] Furthermore, the small plunger seal seat is arranged below or above the large plunger.

[0042] To achieve the above object, the present invention adopts the following technical solutions:

[0043] An application string of a casing gas recovery device includes a casing, a tubing, and a sucker rod. The tubing is arranged in the casing, and a plug, a screen pipe, an oil pump, and a casing gas recovery device are sequentially arranged in the tubing from bottom to top.

[0044] The sucker rod is arranged in the tubing and is connected to the oil pump at the lower end.

[0045] The outer cylinder of the casing gas recovery device is connected to the tubing through a tubing collar, and the small plunger of the casing gas recovery device is connected to the sucker rod through a sucker rod collar and is located in the outer cylinder.

[0046] To achieve the above object, the present invention adopts the following technical solutions:

[0047] A using method of a casing gas recovery device includes the following steps: installing the device on the tubing and lowering it into the well.

[0048] A1. Increase the volume of the gas chamber and decrease the pressure. When the pressure of the gas in the casing is greater than the pressure in the gas chamber and overcomes the intake valve return spring, the intake valve opens, and the casing gas enters the gas chamber through the bottom pipe of the intake port, the intake valve seat, and the intake port passage.

[0049] A2. Decrease the volume of the gas chamber and increase the pressure. The intake valve closes under the action of the intake valve return spring. When the pressure in the gas chamber is greater than the liquid column pressure above the large plunger and overcomes the outlet valve return spring, the outlet valve opens, and the gas in the gas chamber enters the inside of the tubing after passing through the bottom pipe of the outlet port, the outlet valve seat, and the outlet gland.

[0050] A3. The crude oil at the lower part of the casing gas recovery device enters the tubing at the upper part of the casing gas recovery device through the oil inlet, the oil flow channels of the large plunger and the small plunger, and the oil outlet.

[0051] In an embodiment of the present invention:

[0052] A. When the small plunger seal seat is arranged below the large plunger,

[0053] When the pumping rod moves upward and the large plunger moves upward with the pumping rod, the volume of the gas chamber will increase.

[0054] When the pumping rod moves downward and the pumping rod drives the large plunger to move downward under its own weight, the volume of the gas chamber will decrease.

[0055] In an embodiment of the present invention:

[0056] B. When the small plunger seal seat is arranged above the large plunger,

[0057] When the pumping rod moves downward and the pumping rod drives the large plunger to move downward under its own weight, the volume of the gas chamber will increase.

[0058] When the pumping rod moves upward and the large plunger moves upward with the pumping rod, the volume of the gas chamber will decrease.

[0059] The present invention has the following beneficial effects compared with the prior art:

[0060] 1. Utilize the self-weight load of the oil well rod string to compress the gas, without additional energy, more energy-saving;

[0061] 2. Collect the casing gas by compression, the pressure in the casing is not affected by the back pressure, and the casing pressure can be reduced below the back pressure;

[0062] 3. Compress the gas in the casing into the tubing, effectively reduce the density of the well fluid. At the same time, as the oil flow in the tubing rises and the pressure decreases, the gas expands, with gas lift operation, which can effectively reduce the lifting energy consumption and improve the lifting condition of the oil well;

[0063] 4. The stroke of the compressed gas is adjustable within the stroke of the oil well and is larger than that of the surface casing gas collection device, with high efficiency;

[0064] 5. The casing gas is recovered downhole, solving the problem of freezing blockage that occurs in the surface collection of casing gas in winter. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 is a schematic structural diagram of a pipe string for applying a casing gas recovery device of the present invention;

[0066] Figure 2 is a schematic structural diagram of a casing gas recovery device according to Embodiment 1 of the present invention;

[0067] Figure 3 is a schematic structural diagram of a casing gas recovery device according to Embodiment 2 of the present invention;

[0068] In the figure: 1. Sucker rod; 1.1. Sucker rod coupling; 2. Casing gas recovery device; 2.1. Oil outlet; 2.2. Large plunger; 2.3. Large plunger seal; 2.4. Bottom pipe of the gas outlet; 2.5. Compression cover of the large plunger gas outlet; 2.6. Return spring of the gas outlet; 2.7. Gas outlet valve; 2.8. Gas outlet valve seat; 2.9. Outer cylinder; 2.10. Small plunger; 2.11. Oil flow channel; 2.12. Gas chamber; 2.13. Compression cover of the air inlet; 2.14. Return spring of the air inlet; 2.15. Third air inlet channel; 2.16. Air inlet valve; 2.17. Air inlet valve seat; 2.18. Outer shell of the air inlet assembly; 2.19. Bottom pipe of the air inlet; 2.20. Small plunger seal; 2.21. Small plunger seal seat; 2.22. Oil inlet; 3. Oil pipe; 3.1. Oil pipe coupling; 4. Casing; 5. Sucker rod pump; 6. Screen pipe or gas anchor; 7. Plug; 8. Artificial bottom hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0069] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0070] Embodiment 1:

[0071] Please refer to Figure 2, a casing gas recovery device provided by the present invention includes a plunger pipe, an outer cylinder 2.9, and an intake assembly; the plunger pipe is arranged in the outer cylinder 2.9, the plunger pipe is divided into a large plunger 2.2 and a small plunger 2.10, the large plunger 2.2 is a plunger ring arranged on the small plunger 2.10, a small plunger seal seat 2.21 is arranged on the inner wall of the outer cylinder 2.9, an air inlet is arranged in the area between the small plunger seal seat 2.21 and the large plunger 2.2 of the outer cylinder 2.9, and the intake assembly is arranged on the outer wall of the outer cylinder 2.9 and connected to the air inlet.

[0072] Both the upper end and the lower end of the outer cylinder 2.9 are provided with tubing couplings 3.1.

[0073] The intake assembly includes an intake assembly housing 2.18 and an intake port bottom pipe 2.19; the intake assembly housing 2.18 is provided with a second intake channel that penetrates axially, the intake port bottom pipe 2.19 is threadedly connected to the lower end of the second intake channel, in the second intake channel, a first boss is arranged above the intake port bottom pipe 2.19, an intake port valve seat 2.17 is arranged between the intake port bottom pipe 2.19 and the first boss, and the first boss is used to limit the position of the intake port valve seat 2.17; an intake valve 2.16 is installed above the intake port valve seat 2.17, an intake return spring 2.14 is installed above the intake valve 2.16, the upper end of the intake assembly housing 2.18 is provided with an intake port gland 2.13, and the intake return spring 2.14 presses the intake port gland 2.13 upward and the intake valve 2.16 downward, so that the intake valve 2.16 sits on the intake port valve seat 2.17.

[0074] The intake port gland 2.13 gives a certain pre-tightening force to the intake return spring 2.14, so that the intake return spring 2.14 is in a compressed state.

[0075] A first intake channel is arranged at the center of the intake port bottom pipe 2.19; the intake assembly housing 2.18 is provided with a third intake channel 2.15 above the intake port valve seat 2.17 and connected to the intake port, and the air cavity 2.12 formed between the outer cylinder 2.9, the small plunger seal seat 2.21, and the large plunger 2.2 is communicated with the second intake channel.

[0076] The intake port valve seat 2.17 and the inner wall of the second intake channel, and between the intake port gland 2.13 and the intake assembly housing 2.18 are sealed by intake seals.

[0077] The upper end of the small plunger 2.10 is provided with a sucker rod coupling 1.1 for connecting with the upper sucker rod 1, and the small plunger 2.10 is connected to the lower sucker rod by threads.

[0078] The large plunger 2.2 and the small plunger 2.10 can be integrally manufactured or connected by means of threading or other connection methods.

[0079] The small plunger 2.10 has a hollow structure to form an oil flow channel 2.11 for crude oil; an oil outlet 2.1 is provided at the upper end of the small plunger 2.10, and an oil inlet 2.21 is provided at the lower end; the length of the small plunger 2.10 is greater than the production stroke of the oil pump.

[0080] The large plunger 2.2 is provided with an air outlet unit on the circumference. The air outlet unit includes an air outlet channel and an air outlet bottom pipe 2.4; the air outlet bottom pipe 2.4 is provided at the lower end of the air outlet channel, and the air outlet channel is communicated with the air cavity 2.12 through the air outlet bottom pipe 2.4; a second boss is provided above the air outlet bottom pipe 2.4, and an air outlet valve seat 2.8 is provided between the air outlet bottom pipe 2.4 and the second boss. The second boss is used to limit the position of the air outlet valve seat 2.8; an air outlet valve 2.7 is provided above the air outlet valve seat 2.8, and an air outlet return spring 2.6 is provided above the air outlet valve 2.7. The air outlet channel is provided with an air outlet gland 2.5. The air outlet return spring 2.6 pushes up the air outlet gland 2.5 and pushes down the air outlet valve 2.7, so that the air outlet valve 2.7 sits in the air outlet valve seat 2.8. An air hole is provided on the air outlet gland 2.5 to communicate the air outlet channel with the upper part.

[0081] The air outlet gland 2.5 gives a certain pre-tightening force to the air outlet return spring 2.6, so that the air outlet return spring 2.6 is in a compressed state.

[0082] At least two air outlet units are provided and are evenly arranged along the circumference of the large plunger 2.2.

[0083] Between the air outlet gland 2.5 and the large plunger 2.2, and between the air outlet valve seat 2.8 and the air outlet channel are sealed by air outlet seals.

[0084] All the air outlet glands 2.5 in the at least two air outlet units are integrally formed and are connected to the large plunger 2.2 by threading.

[0085] At least two large plunger seals 2.3 are provided between the large plunger 2.2 and the outer cylinder 2.9. The large plunger seals 2.3 are rigid sealing rings or soft seals.

[0086] At least two small plunger seals 2.20 are provided between the small plunger seal seat 2.21 and the small plunger 2.10. The small plunger seals 2.20 are rigid sealing rings or soft seals.

[0087] In this embodiment, the small plunger seal seat 2.21 is provided below the large plunger 2.2.

[0088] Example 2:

[0089] Based on Example 1, please refer to Figure 3 , in this embodiment, the small plunger seal seat 2.21 is arranged above the large plunger 2.2.

[0090] When the sucker rod 1 moves upward, the upper and lower ends of the large plunger 2.2 are affected by the downhole liquid column pressure and the pressure in the gas cavity 2.12. Since the casing gas pressure is relatively small, during most of the upward stroke of the large plunger 2.2, the upward buoyancy of the downhole liquid column on the large piston 2.2 is greater than the upward resistance of the large piston in the gas cavity 2.12. At this time, the load of the sucker rod 1 can be effectively reduced, and the energy consumption of the pumping unit can be reduced; when the pressure in the gas cavity 2.12 is slightly greater than the liquid column pressure, the gas is discharged, and the load change of the sucker rod is not significant.

[0091] Example 3:

[0092] Based on Example 1 or 2, this embodiment provides the application string and usage method of this device.

[0093] Please refer to Figure 1 , an application string of a casing gas recovery device provided by the present invention includes a casing 4, a tubing 3, and a sucker rod 1. The tubing 3 is arranged in the casing. The tubing 3 is sequentially provided with a plug 7, a screen pipe 6, a sucker pump 5, and a casing gas recovery device 2 from bottom to top. The sucker rod 1 is arranged in the tubing 3 and is connected to the sucker pump 5 at the lower end. The outer cylinder 2.9 of the casing gas recovery device 2 is connected to the tubing 3 through a tubing coupling 3.1. The small plunger 2.10 is connected to the sucker rod 1 through a sucker rod coupling 1.1 and is located in the outer cylinder 2.9.

[0094] S1. The process of collecting casing gas using the casing gas recovery device in Example 1:

[0095] A1. When the oil well is producing normally and the sucker rod 1 moves upward, the large plunger 2.2 moves upward with the sucker rod 1. The volume of the gas cavity 2.12 increases and the pressure decreases. When the pressure of the gas in the casing is greater than the pressure in the gas cavity and overcomes the intake port return spring 2.14, the intake valve 2.16 opens, and the casing gas enters the gas cavity 2.12 through the intake port bottom pipe 2.19, the intake port valve seat 2.17, and the intake port channel 2.15;

[0096] A2. When the sucker rod 1 moves downward, under the action of its own weight, the sucker rod drives the large plunger 2.2 to move downward. The volume of the air chamber 2.12 decreases, the pressure increases, and the intake valve 2.16 closes under the action of the intake port return spring 2.14; when the pressure in the air chamber 2.12 is greater than the liquid column pressure above the large plunger 2.2 and overcomes the outlet port return spring 2.6, the outlet valve 2.7 opens. The gas in the air chamber 2.12 enters the inside of the tubing through the outlet bottom pipe 2.4, the outlet valve seat 2.8, and the outlet gland 2.5, thus realizing the transfer of the casing gas to the inside of the tubing.

[0097] A3. At the same time, the crude oil at the lower part of the casing gas recovery device 2 enters the tubing 3 at the upper part of the casing gas recovery device 2 through the oil inlet 2.21, the oil flow channels 2.11 of the large plunger 2.2 and the small plunger 2.10, and the oil outlet 2.1.

[0098] As the crude oil and gas move upward, the liquid column pressure decreases and the gas expands, realizing the gas lift operation during the crude oil lifting process and improving the mechanical lifting effect.

[0099] S2. The process of collecting casing gas using the casing gas recovery device in Embodiment 2:

[0100] B1. When the sucker rod 1 moves downward during the normal production of the oil well, under the action of its own weight, the sucker rod drives the large plunger 2.2 to move downward. The volume of the air chamber 2.12 increases and the pressure decreases. When the pressure of the gas in the casing is greater than the pressure in the air chamber and overcomes the intake port return spring 2.14, the intake valve 2.16 opens, and the casing gas enters the air chamber 2.12 through the intake bottom pipe 2.19, the intake valve seat 2.17, and the intake port channel 2.15.

[0101] B2. When the sucker rod 1 moves upward, the large plunger 2.2 moves upward with the sucker rod 1. The volume of the air chamber 2.12 decreases, the pressure increases, and the intake valve 2.16 closes under the action of the intake port return spring 2.14; when the pressure in the air chamber 2.12 is greater than the liquid column pressure above the large plunger 2.2 and overcomes the outlet port return spring 2.6, the outlet valve 2.7 opens. The gas in the air chamber 2.12 enters the inside of the tubing through the outlet bottom pipe 2.4, the outlet valve seat 2.8, and the outlet gland 2.5, thus realizing the transfer of the casing gas to the inside of the tubing.

[0102] B3. At the same time, the crude oil at the lower part of the casing gas recovery device 2 enters the tubing 3 at the upper part of the casing gas recovery device 2 through the oil inlet 2.21, the oil flow channels 2.11 of the large plunger 2.2 and the small plunger 2.10, and the oil outlet 2.1.

[0103] As the crude oil and gas move upward, the liquid column pressure decreases and the gas expands, realizing the gas lift operation during the crude oil lifting process and improving the mechanical lifting effect.

[0104] In this application, all components that are not elaborated on, as well as the connection methods of each component in this application, belong to the well-known technologies in this technical field. They can be directly applied and will not be elaborated further.

[0105] In the present invention, the term "plurality" refers to two or more, unless otherwise clearly defined. Terms such as "installed", "connected", "joined", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "joined" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0106] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention.

[0107] In the description of this specification, the description of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0108] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A casing gas recovery device, comprising a plunger tube and an outer cylinder. The plunger tube is arranged in the outer cylinder. It is characterized in that the plunger tube is divided into a large plunger and a small plunger. The large plunger is sleeved on the small plunger. A small plunger seal seat is arranged on the inner wall of the outer cylinder, and the small plunger is inserted into the small plunger seal seat; an air cavity is formed among the outer cylinder, the small plunger seal seat and the large plunger. An air inlet assembly is arranged on the outer cylinder in the air cavity area; an air outlet unit is arranged on the large plunger.

2. The casing gas recovery device according to claim 1, wherein The outer cylinder is provided with an air inlet in the air cavity area. The air inlet assembly is arranged on the outer wall of the outer cylinder and is connected with the air inlet; the air inlet assembly comprises an air inlet assembly housing and an air inlet bottom pipe; a first air inlet channel is arranged at the center of the air inlet bottom pipe; the air inlet assembly housing is provided with an axially penetrating second air inlet channel, and the air inlet bottom pipe is connected with the lower end of the second air inlet channel; in the second air inlet channel, a first boss is arranged above the air inlet bottom pipe, and an air inlet valve seat is arranged between the air inlet bottom pipe and the first boss; an air inlet valve is installed above the air inlet valve seat, an air inlet return spring is installed above the air inlet valve, and an air inlet gland is arranged at the upper end of the air inlet assembly housing to make the air inlet return spring in a compressed state; the air inlet return spring pushes the air inlet gland upward and the air inlet valve downward, so that the air inlet valve sits on the air inlet valve seat; the air inlet assembly housing is provided with a third air inlet channel above the air inlet valve seat to communicate the air cavity with the second air inlet channel.

3. The casing gas recovery device according to claim 2, characterized in that, Seals are arranged between the air inlet valve seat and the inner wall of the second air inlet channel, and between the air inlet gland and the air inlet assembly housing through air inlet seals.

4. A casing gas recovery device according to claim 1, characterized in that, The air outlet unit comprises an air outlet channel and an air outlet bottom pipe; the air outlet bottom pipe is arranged at the lower end of the air outlet channel, and the air outlet channel is communicated with the air cavity through the air outlet bottom pipe; a second boss is arranged above the air outlet bottom pipe, and an air outlet valve seat is arranged between the air outlet bottom pipe and the second boss; an air outlet valve is arranged above the air outlet valve seat, an air outlet return spring is arranged above the air outlet valve, and an air outlet gland is arranged on the air outlet channel to make the air outlet return spring in a compressed state; the air outlet return spring pushes the air outlet gland upward and the air outlet valve downward, so that the air outlet valve sits in the air outlet valve seat; an air outlet hole is arranged on the air outlet gland to communicate the air outlet channel with the upper part.

5. The casing gas recovery device according to claim 4, wherein, Seals are arranged between the air outlet gland and the large plunger, and between the air outlet valve seat and the air outlet channel through air outlet seals; at least two air outlet units are arranged and are evenly arranged along the circumferential direction of the large plunger; all the air outlet glands in the at least two air outlet units are integrally formed and are connected with the large plunger through threads.

6. The casing gas recovery device according to claim 1, characterized in that, The small plunger is of a hollow structure, and an oil flow channel for crude oil is formed in the center; an oil outlet is arranged at the upper end of the small plunger, and an oil inlet is arranged at the lower end of the small plunger; the length of the small plunger is greater than the production stroke of the oil pump; at least two large plunger seals are arranged between the large plunger and the outer cylinder, and the large plunger seals are rigid sealing rings or soft seals; at least two small plunger seals are arranged between the small plunger seal seat and the small plunger, and the small plunger seals are rigid sealing rings or soft seals; Both the upper and lower ends of the outer cylinder are provided with tubing couplings. The upper end of the small plunger is provided with a sucker rod coupling for connecting with the upper sucker rod, and the lower end of the small plunger is provided with a sucker rod thread for connecting with the lower sucker rod. The large plunger and the small plunger are integrally manufactured or connected by threads.

7. A casing gas recovery device according to any one of claims 1-6, characterized in that, The small plunger seal seat is arranged below or above the large plunger.

8. An application string of a casing gas recovery device, comprising a casing, a tubing, and a sucker rod. The tubing is arranged in the casing. It is characterized in that The tubing is sequentially provided with a plug, a screen pipe, a sucker pump, and a casing gas recovery device from bottom to top. The sucker rod is arranged in the tubing and is connected to the sucker pump at the lower end. The outer cylinder of the casing gas recovery device is connected to the tubing through a tubing coupling, and the small plunger of the casing gas recovery device is connected to the sucker rod through a sucker rod coupling and is located in the outer cylinder.

9. A method for using a casing gas recovery device, characterized in that, It includes the following steps: Install the device on the tubing and lower it into the well. A1. Increase the volume of the gas chamber and decrease the pressure. When the pressure of the gas in the casing is greater than the pressure in the gas chamber and overcomes the intake valve return spring, the intake valve opens, and the casing gas enters the gas chamber through the intake port bottom pipe, the intake valve seat, and the intake port channel. A2. Decrease the volume of the gas chamber and increase the pressure. The intake valve closes under the action of the intake valve return spring. When the pressure in the gas chamber is greater than the liquid column pressure above the large plunger and overcomes the outlet valve return spring, the outlet valve opens, and the gas in the gas chamber enters the inside of the tubing after passing through the outlet port bottom pipe, the outlet valve seat, and the outlet gland. A3. The crude oil at the lower part of the casing gas recovery device enters the tubing above the casing gas recovery device through the oil inlet, the oil flow channels of the large plunger and the small plunger, and the oil outlet.

10. The usage method of a casing gas recovery device according to claim 9, characterized in that A. When the small plunger seal seat is arranged below the large plunger, When the sucker rod moves upward, the large plunger moves upward with the sucker rod, which will increase the volume of the gas chamber. When the sucker rod moves downward, the sucker rod drives the large plunger to move downward under its own weight, which will decrease the volume of the gas chamber. B. When the small plunger seal seat is arranged above the large plunger, When the sucker rod moves downward, the sucker rod drives the large plunger to move downward under its own weight, which will increase the volume of the gas chamber. When the sucker rod moves upward, the large plunger moves upward with the sucker rod, which will decrease the volume of the gas chamber.

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