Tight oil gas CO2 huff-puff flow self-adjusting injection pump

Abstract

The invention discloses a compact oil gas CO2 throughput flow self-adjusting injection pump, and relates to the technical field of carbon dioxide injection pump transformation and oil increasing. The plunger is divided into a front plunger and a rear plunger, the diameters of a front section shaft, a middle section shaft and a rear section shaft of the front plunger are sequentially increased, the front section shaft extends into the pump body, a counter bore is formed in the left end face of the rear plunger, the rear section shaft is in clearance fit with the counter bore through a sealing ring, the rear plunger is connected with a limiting gland, and an inner hole of the limiting gland is in clearance fit with the middle section shaft. A compression spring is installed between the limiting gland and the left end face of the rear section shaft. The CO2 injection pump has the beneficial effects that the overall structure of an existing CO2 injection pump is not changed, the plunger is transformed into the front plunger and the rear plunger, the injection pressure in the pump body is utilized, the position of the floating piston is changed, and the volume of liquid CO2 injected into the pump body every time is changed, so that the flow of the injection pump is automatically adjusted, and when the stratum injection pressure is high, the liquid CO2 is automatically injected into the pump body. And when the flow of the injection pump is reduced and the formation injection pressure is low, the flow of the injection pump is increased, so that instant flow regulation is realized without adding equipment such as a frequency converter and a PLC (Programmable Logic Controller).

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide injection pump modification and oil-increasing technology, and in particular to a tight oil and gas CO2 throughput flow self-regulating injection pump. Background Art

[0002] CO2 huff-and-puff oil recovery technology refers to injecting CO2 into oil and gas reservoirs. CO2 can flow into the micropores of the formation and dissolve in the crude oil, reducing the viscosity of the crude oil and expanding its volume, thereby reducing the difficulty of crude oil extraction, increasing production, and achieving the purpose of increasing crude oil recovery. At the same time, during the CO2 huff-and-puff oil recovery process, a part of the CO2 will be sealed in the formation, which reduces CO2 emissions while increasing the recovery rate. Low-permeability tight oil and gas reservoirs have the characteristics of low permeability and small pore throats. The fluid flow resistance in them is relatively high, and a higher pressure is often required to overcome this resistance. Therefore, liquid CO2 is generally used for low-permeability tight oil and gas reservoirs, and a three-plunger injection pump is used to inject liquid CO2 to achieve the purpose of oil recovery. The existing public technologies all control the flow rate of carbon dioxide injected into the oil and gas reservoir by monitoring the injection pressure of CO2 through a pressure meter. That is, when the CO2 pressure is monitored to increase, the flow rate of CO2 injected into the oil and gas reservoir is reduced. By monitoring and changing the flow rate of the injection pump, there is a lag in the adjustment time. At the same time, PLC and frequency converter are also needed to control the injection pump flow rate, which increases equipment investment. Summary of the invention

[0003] In order to solve the problem that the existing three-plunger injection pump needs to adjust the flow rate according to the formation pressure when injecting CO2, the present invention provides a tight oil and gas CO2 throughput flow self-regulating injection pump.

[0004] The technical solution provided by the present invention is: a self-regulating injection pump for dense oil and gas CO2 throughput flow, including a pump body, a plunger, a packing gland and a packing packing, the plunger is divided into a front plunger and a rear plunger, the front plunger is connected to the pump body through the packing packing and sealed, the rear plunger is connected to the power end of the injection pump, the front plunger is divided into a front shaft, a middle shaft and a rear shaft from left to right, the diameters of the front shaft, the middle shaft and the rear shaft increase in sequence, the front shaft extends into the pump body, a countersunk hole is opened on the left end face of the rear plunger, the rear shaft extends into the countersunk hole, and the rear shaft is connected to the countersunk hole The left end face of the rear plunger is connected to the limit cover through a flange and bolts, and the inner hole of the limit cover is matched with the clearance of the middle shaft. A compression spring is installed between the limit cover and the left end face of the rear shaft. The front plunger is provided with a center hole that passes through the left and right sides. A floating piston is arranged in the center hole. The floating piston is matched with the clearance of the center hole through a sealing ring. The left end of the center hole is threadedly connected to a limit nut. The inner hole of the limit nut is smaller than the outer circle of the floating piston. The space formed by the right end of the floating piston, the front plunger and the rear plunger is filled with hydraulic oil.

[0005] A capsule and a retaining ring are provided between the limit gland and the compression spring. The capsule is located on one side of the limit gland. The outer side of the capsule is fixedly connected to a section of steel pipe by vulcanization. A through hole is opened on the limit gland. The steel pipe passes through the through hole and extends out of the limit gland to connect the needle-type bypass valve and the one-way valve. The capsule is filled with hydraulic oil.

[0006] A first annular hole is opened on the left side of the right end surface of the front plunger, and the first annular hole is opened to the front section shaft position. A second annular hole is opened on the right end surface of the front plunger, and the diameter of the second annular groove is larger than that of the first annular hole. The second annular hole is opened to the middle section shaft position. The right end of the first annular hole is threadedly sealed and connected to a sealing gland. The enclosed space formed by the sealing gland and the first annular hole is filled with capillary matter. The enclosed space formed by the sealing gland and the first annular hole is filled with working fluid. The enclosed space formed by the sealing gland and the first annular hole is sucked in a negative pressure state, and a spiral blade is welded on the outer circle of the front section shaft outside the pump body.

[0007] The space formed by the right end of the floating piston, the front plunger and the rear plunger is filled with hydraulic oil, so that the floating piston is located in the middle of the center hole.

[0008] The beneficial effects of the present invention are as follows: the present invention does not change the overall structure of the existing CO2 injection pump, but transforms the plunger into a front plunger and a rear plunger, and utilizes the injection pressure in the pump body to change the position of the floating piston, thereby changing the effective volume (displacement) of the pump body, and thus changing the volume of liquid CO2 injected into the pump body each time, thereby automatically adjusting the flow rate of the injection pump, that is, when the formation injection pressure is high, the flow rate of the injection pump is reduced, and when the formation injection pressure is low, the flow rate of the injection pump is increased, thereby realizing instant flow rate regulation, without the need to add frequency converters, PLCs and other equipment; At the same time, the flow range of the injection pump can be adjusted by adjusting the compression degree of the compression spring and adjusting the stroke of the plunger; The split structure of the plunger allows a heat pipe system to be set up inside the plunger to transfer the heat generated by the friction between the plunger and the packing to the outside, thereby reducing the temperature of the friction part of the plunger and avoiding the gasification of liquid CO2 in the pump body. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Attached Figure 1 It is a schematic diagram of the structure of the present invention; Attached Figure 2 Yes Figure 1 A magnified image of point A; Attached Figure 3 It is a structural schematic diagram of the front plunger in the present invention; Attached Figure 4 It is a structural schematic diagram of the rear plunger in the present invention.

[0010] In the figure: 1-front plunger, 101-front section shaft, 102-middle section shaft, 103-rear section shaft, 104-center hole, 105-first annular hole, 106-second annular hole, 2-rear plunger, 201-countersunk hole, 3-pump body, 4-packing, 5-packing gland, 6-limiting gland, 601-through hole, 7-compression spring, 8-floating piston, 9-limiting nut, 10-retaining ring, 11-capsule, 12-steel pipe, 13-needle bypass valve, 14-check valve, 15-sealing gland, 16-capillary, 17-spiral blade. DETAILED DESCRIPTION

[0011] like Figures 1 to 4 As shown, a self-regulating injection pump for dense oil and gas CO2 throughput flow includes a pump body 3, a plunger, a packing gland 5 and a packing 4. The plunger is divided into a front plunger 1 and a rear plunger 2. The front plunger 1 is sealed and movably connected to the pump body 3 through the packing 4, and the rear plunger 2 is connected to the power end of the injection pump. The front plunger 1 is divided into a front shaft 101, a middle shaft 102 and a rear shaft 103 from left to right. The diameters of the front shaft 101, the middle shaft 102 and the rear shaft 103 increase successively. The front shaft 101 extends into the pump body 3. A countersunk hole 201 is opened on the left end face of the rear plunger 2. The rear shaft 103 extends into the countersunk hole 201. The rear shaft 103 and the countersunk hole 2 01 is fitted with a sealing ring through a clearance, and the left end face of the rear plunger 2 is connected to the limiting cover 6 through a flange and bolts. The inner hole of the limiting cover 6 is fitted with a clearance with the middle shaft 102. A compression spring 7 is installed between the limiting cover 6 and the left end face of the rear shaft 103. The front plunger 1 is provided with a center hole 104 that passes through the left and right sides. A floating piston 8 is arranged in the center hole 104. The floating piston 8 is fitted with a sealing ring through the center hole 104. The left end of the center hole 104 is threadedly connected to a limiting nut 9. The inner hole of the limiting nut 9 is smaller than the outer circle of the floating piston 8. The space formed by the right end of the floating piston 8, the front plunger 1 and the rear plunger 2 is filled with hydraulic oil.

[0012] When CO2 is injected into the formation for huff and puff recovery, the plunger moves to the left to inject liquid CO2 into the formation. When the formation pressure increases, since the cross-sectional area of ​​the rear shaft 103 is larger than the cross-sectional area of ​​the front shaft 101, the pressure in the pump body 3 (i.e., the outlet pressure pushed by the plunger) is transmitted to the right end face of the rear shaft 103 through the floating piston 8. The thrust acting on the front shaft 101 is smaller than the thrust of the rear shaft 103. The pressure pushes the front plunger 1 to move leftward relative to the rear plunger 2. At this time, the floating piston 8 moves to the right, and the liquid CO2 in the pump body 3 flows into the center hole on the left side of the floating piston 8. The effective volume of the pump body 3 is reduced, thereby reducing the volume of liquid CO2 discharged by the pump body 3, that is, reducing the flow rate of the injection pump. Conversely, when the formation pressure decreases, under the action of the compression spring 7, the front plunger 1 moves to the right relative to the rear plunger 2, and the floating piston 8 moves to the left, and the flow rate of the injection pump increases.

[0013] The present invention does not change the overall structure of the existing CO2 injection pump, but transforms the plunger into a front plunger 1 and a rear plunger 2. The injection pressure in the pump body 3 is used to change the position of the floating piston 8, thereby changing the effective volume (displacement) of the pump body 3, and thus changing the volume of liquid CO2 injected into the pump body 3 each time, thereby automatically adjusting the flow of the injection pump, that is, when the formation injection pressure is high, the flow of the injection pump is reduced, and when the formation injection pressure is low, the flow of the injection pump is increased, thereby realizing instant flow regulation without adding equipment such as frequency converters and PLCs. A capsule 11 and a retaining ring 10 are provided between the limiting gland 6 and the compression spring 7. The capsule 11 is located on one side of the limiting gland 6. A section of steel pipe 12 is fixedly connected to the outer side of the capsule 11 by vulcanization. A through hole 601 is opened on the limiting gland 6. The steel pipe 12 passes through the through hole 601 and extends out of the limiting gland 6 to connect with a needle-type bypass valve 13 and a one-way valve 14. The capsule 11 is filled with hydraulic oil. The one-way valve 14 is used to inject hydraulic oil into the capsule 11. The needle-type bypass valve 13 is used to discharge the hydraulic oil in the capsule 11, thereby changing the volume of the capsule 11 and adjusting the internal compression degree of the compression spring 7, that is, changing the stroke of the front plunger 1.

[0014] By adjusting the compression degree of the compression spring 7, the stroke of the plunger is adjusted, thereby adjusting the flow rate variation range of the injection pump.

[0015] The front plunger 1 has a first annular hole 105 on the left side of the right end surface, and the first annular hole 105 is opened to the front section shaft 101. The front plunger 1 has a second annular hole 106 on the right end surface. The diameter of the second annular groove 106 is larger than that of the first annular hole 105. The second annular hole 106 is opened to the middle section shaft 102. The right end of the first annular hole 105 is threadedly connected to the sealing gland 15. The closed space formed by the sealing gland 15 and the first annular hole 105 is filled with a capillary 16. The sealing gland 15 and the first annular hole 105 are connected to each other. The enclosed space formed is filled with working fluid, and the enclosed space formed by the sealing gland 15 and the first annular hole 105 is sucked into a negative pressure state to form a heat pipe system. The heat pipe system has the advantage of real-time heat transfer and high heat transfer efficiency. The heat generated by the friction between the plunger and the packing 4 can be transferred to the outside, reducing the temperature of the friction part of the plunger and avoiding the gasification of the liquid CO2 in the pump body 3. The outer circle of the front section shaft 101 is welded with spiral blades 17 outside the pump body 3 to play a heat dissipation role. During the high-speed forward and backward stroke of the plunger, the spiral blade 17 can cause the front plunger 1 to rotate slightly under the action of air resistance, reducing the probability of eccentric wear of the packing 4. The spiral blade 17 can be made into a one-way ventilation structure to allow the front plunger 1 to rotate continuously in one direction.

[0016] The space formed by the right end of the floating piston 8, the front plunger 1 and the rear plunger 2 is filled with hydraulic oil, so that the floating piston 8 is located in the middle of the center hole 104. When the formation pressure changes, the floating piston 8 can move left and right.

Claims

1. A dense oil and gas CO2 throughput self-regulating injection pump, comprising a pump body (3), a plunger, a packing gland (5) and a packing (4), characterized in that: The plunger is divided into a front plunger (1) and a rear plunger (2). The front plunger (1) is connected to a pump body (3) in a sealed and movable manner through a packing (4). The rear plunger (2) is connected to the power end of the injection pump. The front plunger (1) is divided into a front shaft (101), a middle shaft (102) and a rear shaft (103) from left to right. The diameters of the front shaft (101), the middle shaft (102) and the rear shaft (103) increase in sequence. The front shaft (101) extends into the pump body (3). A countersunk hole (201) is opened on the left end surface of the rear plunger (2). The rear shaft (103) extends into the countersunk hole (201). The rear shaft (103) and the countersunk hole (201) are matched through a sealing ring gap. The left end of the rear plunger (2) The front and rear surfaces are connected to a limit gland (6) through flanges and bolts. The inner hole of the limit gland (6) is clearance-matched with the middle shaft (102). A compression spring (7) is installed between the limit gland (6) and the left end surface of the rear shaft (103). The front plunger (1) is provided with a center hole (104) which passes through the left and right sides. A floating piston (8) is arranged in the center hole (104). The floating piston (8) is clearance-matched with the center hole (104) through a sealing ring. The left end of the center hole (104) is threadedly connected to a limit nut (9). The inner hole of the limit nut (9) is smaller than the outer circle of the floating piston (8). The space formed by the right end of the floating piston (8), the front plunger (1) and the rear plunger (2) is filled with hydraulic oil.

2. A CO2 throughput self-regulating injection pump for dense oil and gas according to claim 1, characterized in that: A capsule (11) and a retaining ring (10) are provided between the limit gland (6) and the compression spring (7); the capsule (11) is located on one side of the limit gland (6); a section of steel pipe (12) is fixedly connected to the outer side of the capsule (11) by vulcanization; a through hole (601) is provided on the limit gland (6); the steel pipe (12) passes through the through hole (601) and extends out of the limit gland (6) to connect to a needle-type bypass valve (13) and a one-way valve (14); and the capsule (11) is filled with hydraulic oil.

3. A CO2 throughput self-regulating injection pump for dense oil and gas according to claim 1, characterized in that: The front plunger (1) is provided with a first annular hole (105) on the left side of the right end surface, the first annular hole (105) is opened to the front section shaft (101), the front plunger (1) is provided with a second annular hole (106) on the right end surface, the diameter of the second annular groove (106) is larger than that of the first annular hole (105), the second annular hole (106) is opened to the middle section shaft (102), the right end of the first annular hole (105) is threadedly connected to a sealing gland (15), a closed space formed by the sealing gland (15) and the first annular hole (105) is filled with a capillary (16), the closed space formed by the sealing gland (15) and the first annular hole (105) is filled with a working fluid, the closed space formed by the sealing gland (15) and the first annular hole (105) is in a negative pressure state when suctioned, and a spiral blade (17) is welded to the outer circle of the front section shaft (101) outside the pump body (3).

4. A CO2 throughput self-regulating injection pump for dense oil and gas according to claim 1, characterized in that: The space formed by the right end of the floating piston (8), the front plunger (1) and the rear plunger (2) is filled with hydraulic oil, so that the floating piston (8) is located in the middle of the central hole (104).

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