A tight oil and gas CO2 huff and puff flow rate self-regulating injection pump

Abstract

A self-regulating CO2 injection pump for tight oil and gas belongs to the field of CO2 injection pump modification and oil enhancement technology. The plunger consists of a front plunger and a rear plunger. The diameters of the front, middle, and rear shafts of the front plunger increase sequentially. The front shaft extends into the pump body. A countersunk hole is formed on the left end face of the rear plunger. The rear shaft and the countersunk hole are fitted with a sealing ring. The rear plunger is connected to a limiting cap. The inner hole of the limiting cap is fitted with the middle shaft. A compression spring is installed between the limiting cap and the left end face of the rear shaft. The beneficial effects of this invention are: This invention does not change the overall structure of the existing CO2 injection pump. By modifying the plunger into a front and rear plunger, and utilizing the injection pressure within the pump body to change the position of the floating piston, the volume of liquid CO2 injected into the pump body each time is changed, thereby automatically adjusting the injection pump flow rate. That is, when the formation injection pressure is high, the injection pump flow rate decreases; when the formation injection pressure is low, the injection pump flow rate increases, achieving real-time flow regulation without the need for additional frequency converters, PLCs, or other equipment.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide injection pump modification and oil enhancement technology, and in particular to a tight oil-gas CO2 throughput self-adjusting injection pump. Background Technology

[0002] CO2 huff and puff 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 and expanding the volume of the crude oil, thereby reducing the difficulty of crude oil extraction, increasing production, and achieving the goal of improving crude oil recovery. At the same time, during the CO2 huff and puff process, some CO2 will be sealed in the formation, achieving CO2 emission reduction while improving recovery. Low-permeability tight oil and gas reservoirs are characterized by low permeability and small pore throats, resulting in high flow resistance of fluids. High pressure is often required to overcome this resistance. Therefore, liquid CO2 is generally selected 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 displacement.

[0003] Existing publicly available technologies control the flow rate of carbon dioxide injected into oil and gas reservoirs by monitoring the CO2 injection pressure using pressure gauges. That is, when the CO2 pressure is detected to rise, the CO2 injection flow rate 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. In addition, PLCs and frequency converters are required to control the injection pump flow rate, which increases equipment investment. Summary of the Invention

[0004] To address the issue that existing three-plunger injection pumps require adjusting the CO2 injection flow rate based on formation pressure, this invention provides a tight oil and gas CO2 throughput self-regulating injection pump.

[0005] The technical solution provided by this invention is: a tight oil and gas CO2 huff and puff flow self-regulating injection pump, comprising a pump body, a plunger, a packing gland, and packing. The plunger is divided into a front plunger and a rear plunger. The front plunger is sealed and movablely connected to the pump body through the packing. The rear plunger is connected to the power end of the injection pump. The front plunger is divided into a front shaft section, a middle shaft section, and a rear shaft section from left to right. The diameters of the front shaft section, the middle shaft section, and the rear shaft section increase sequentially. The front shaft section extends into the pump body. A countersunk hole is opened on the left end face of the rear plunger, and the rear shaft section extends into the countersunk hole. The rear shaft section communicates with the countersunk hole. The left end face of the rear plunger is connected to the limiting gland via a flange and bolts through a clearance fit with the sealing ring. The inner hole of the limiting gland is clearance fit with the middle shaft. A compression spring is installed between the limiting gland and the left end face of the rear shaft. The front plunger has a through-hole that runs from left to right. A floating piston is installed in the center hole. The floating piston is clearance fit with the center hole through a sealing ring. The left end of the center hole is threaded to a limiting nut. The inner hole of the limiting nut is smaller than the outer circle of the floating piston. Hydraulic oil is filled in the space formed by the right end of the floating piston, the front plunger, and the rear plunger.

[0006] A capsule and a retaining ring are provided between the limiting pressure cover and the compression spring. The capsule is located on one side of the limiting pressure cover. A section of steel pipe is fixedly connected to the outside of the capsule by vulcanization. A through hole is opened on the limiting pressure cover. The steel pipe passes through the through hole and extends out of the limiting pressure cover, connecting to a needle bypass valve and a check valve. The capsule is filled with hydraulic oil.

[0007] The front plunger has a first annular hole on its right end facing left, extending to the front shaft section. The front plunger also has a second annular hole on its right end face, with the diameter of the second annular groove being larger than that of the first annular hole. The second annular hole extends to the middle shaft section. The right end of the first annular hole is threaded to connect to a sealing gland. The sealed space formed by the sealing gland and the first annular hole is filled with capillary material. The sealed space formed by the sealing gland and the first annular hole is filled with working fluid. The sealed space formed by the sealing gland and the first annular hole is under negative pressure during suction. Spiral blades are welded to the outer circumference of the front shaft outside the pump body.

[0008] Hydraulic oil is filled in the space formed by the right end of the floating piston, the front plunger, and the rear plunger, so that the floating piston is located in the middle of the central hole.

[0009] The beneficial effects of this invention are as follows: This invention does not change the overall structure of the existing CO2 injection pump, but modifies the plunger into a front plunger and a rear plunger. By utilizing the injection pressure in the pump body, the position of the floating piston is changed, thereby changing the effective volume (displacement) of the pump body, which in turn changes the volume of liquid CO2 injected into the pump body each time. This allows for automatic adjustment of the injection pump flow rate. That is, when the formation injection pressure is high, the injection pump flow rate decreases, and when the formation injection pressure is low, the injection pump flow rate increases, achieving real-time flow regulation without the need to add frequency converters, PLCs, or other equipment.

[0010] At the same time, the flow rate variation range of the injection pump can be adjusted by adjusting the degree of compression of the compression spring and the stroke of the plunger.

[0011] The split-type plunger structure allows for the installation of a heat pipe system 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 plunger friction area and preventing the liquid CO2 inside the pump from vaporizing. Attached Figure Description

[0012] Appendix Figure 1 This is a schematic diagram of the structure of the present invention;

[0013] Appendix Figure 2 It is attached Figure 1 Enlarged view of point A;

[0014] Appendix Figure 3 This is a schematic diagram of the front plunger structure in this invention;

[0015] Appendix Figure 4 This is a schematic diagram of the rear plunger in this invention.

[0016] In the diagram: 1-Front plunger, 101-Front section shaft, 102-Middle section shaft, 103-Rear section shaft, 104-Center hole, 105-First ring hole, 106-Second ring hole, 2-Rear plunger, 201-Counterhead, 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-Bug, 12-Steel pipe, 13-Needle bypass valve, 14-Check valve, 15-Sealing gland, 16-Capillary material, 17-Helical blade. Detailed Implementation

[0017] like Figures 1-4 As shown, a tight oil and gas CO2 huff and puff flow self-regulating injection pump includes a pump body 3, plungers, a packing gland 5, and packing 4. The plungers are divided into a front plunger 1 and a rear plunger 2. The front plunger 1 is connected to the pump body 3 in a sealed and movable manner through the 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 sequentially. 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, and the rear shaft 103 extends into the countersunk hole 201. The rear shaft 103 and the countersunk hole 201 are connected. 01. Through a clearance fit with a sealing ring, the left end face of the rear plunger 2 is connected to a limiting cover 6 via a flange and bolts. The inner hole of the limiting cover 6 is clearance fit 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 has a through-hole 104. A floating piston 8 is installed in the center hole 104. The floating piston 8 is clearance fit with the center hole 104 via a sealing ring. The left end of the center hole 104 is threaded to a limiting nut 9. The inner hole of the limiting nut 9 is smaller than the outer circle of the floating piston 8. Hydraulic oil is filled in the space formed by the right end of the floating piston 8, the front plunger 1, and the rear plunger 2.

[0018] When injecting CO2 into the formation for oil displacement, the plunger moves to the left to inject liquid CO2 into the formation. When the formation pressure increases, because the cross-sectional area of ​​the rear shaft 103 is larger than that of the front shaft 101, the pressure inside the pump body 3 (i.e., the outlet pressure of 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 less than the thrust of the rear shaft 103. The pressure pushes the front plunger 1 to the left 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 central hole on the left side of the floating piston 8. The effective volume of the pump body 3 decreases, thereby reducing the volume of liquid CO2 discharged from the pump body 3, which also reduces 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, the floating piston 8 moves to the left, and the flow rate of the injection pump increases.

[0019] This invention does not change the overall structure of the existing CO2 injection pump, but modifies the plunger into a front plunger 1 and a rear plunger 2. By utilizing the injection pressure inside the pump body 3, the position of the floating piston 8 is changed, thereby changing the effective volume (displacement) of the pump body 3, which in turn changes the volume of liquid CO2 injected into the pump body 3 each time. This allows for automatic adjustment of the injection pump flow rate. Specifically, when the formation injection pressure is high, the injection pump flow rate decreases, and when the formation injection pressure is low, the injection pump flow rate increases, achieving real-time flow regulation without the need to add frequency converters, PLCs, or other equipment.

[0020] A capsule 11 and a retaining ring 10 are provided between the limiting cover 6 and the compression spring 7. The capsule 11 is located on one side of the limiting cover 6. A steel pipe 12 is fixedly connected to the outside of the capsule 11 by vulcanization. The limiting cover 6 has a through hole 601. The steel pipe 12 passes through the through hole 601 and extends out of the limiting cover 6, and is connected to a needle 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, and the needle 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.

[0021] By adjusting the degree of compression of the compression spring 7, the stroke of the plunger is adjusted, thereby regulating the range of flow variation of the injection pump.

[0022] The front plunger 1 has a first annular hole 105 on its right end face, extending to the front shaft 101. The front plunger 1 also has a second annular hole 106 on its right end face, with a diameter larger than the first annular hole 105. The second annular hole 106 extends to the middle shaft 102. A sealing cap 15 is threaded to the right end of the first annular hole 105. The sealed space formed by the sealing cap 15 and the first annular hole 105 is filled with capillary material 16. The enclosed space is filled with working fluid. The enclosed space formed by the sealing cap 15 and the first annular hole 105 is under negative pressure, thus forming a heat pipe system. The heat pipe system has the advantage of real-time heat transfer and high heat transfer efficiency. It can transfer the heat generated by the friction between the plunger and the packing 4 to the outside, reduce the temperature of the plunger friction part, and prevent the liquid CO2 in the pump body 3 from vaporizing. The outer circle of the front shaft 101 is welded with spiral blades 17 outside the pump body 3 to play a heat dissipation role.

[0023] During the high-speed stroke of the plunger, the helical blade 17 can cause the front plunger 1 to rotate slightly under the action of air resistance, reducing the probability of uneven wear of the packing 4. The helical blade 17 can be made into a one-way ventilation structure, so that the front plunger 1 rotates continuously in one direction.

[0024] Hydraulic oil is filled in the space formed by the right end of the floating piston 8, the front plunger 1, and the rear plunger 2, so that the floating piston 8 is located in the middle of the central hole 104. When the formation pressure changes, the floating piston 8 can move left and right.

Claims

1. A tight oil-gas CO2 huff and puff flow self-regulating injection pump, comprising a pump body (3), a plunger, a packing gland (5), and 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 the pump body (3) by a sealed moving connection through 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 sequentially. The front shaft (101) extends into the pump body (3). The left end face of the rear plunger (2) has a countersunk hole (201). The rear shaft (103) extends into the countersunk hole (201). The rear shaft (103) and the countersunk hole (201) are fitted with a sealing ring through a clearance fit. The left end of the rear plunger (2) The limiting cover (6) is connected to the face via flange and bolts. The inner hole of the limiting cover (6) is clearance-fitted with the middle section shaft (102). A compression spring (7) is installed between the left end face of the limiting cover (6) and the rear section shaft (103). The front plunger (1) has a through center hole (104) that runs from left to right. A floating piston (8) is provided in the center hole (104). The floating piston (8) is clearance-fitted with the center hole (104) via a sealing ring. The left end of the center hole (104) is threaded with a limiting nut (9). The inner hole of the limiting nut (9) is smaller than the outer circle of the floating piston (8). Hydraulic oil is filled in the space formed by the right end of the floating piston (8), the front plunger (1), and the rear plunger (2). The front plunger (1) has a first annular hole (105) on the right end facing left. The first annular hole (105) extends to the front shaft (101). The front plunger (1) has a second annular hole (106) on the right end face. The diameter of the second annular hole (106) is larger than that of the first annular hole (105). The second annular hole (106) extends to the middle shaft (102). The right end of the first annular hole (105) is threaded to seal the sealing cover (15). The sealed space formed by the sealing cover (15) and the first annular hole (105) is filled with capillary material (16). The sealed space formed by the sealing cover (15) and the first annular hole (105) is filled with working fluid. The sealed space formed by the sealing cover (15) and the first annular hole (105) is under negative pressure during suction. The outer circle of the front shaft (101) is welded with a spiral blade (17) outside the pump body (3).

2. The tight oil-gas CO2 huff and puff flow rate self-regulating injection pump according to claim 1, characterized in that: A capsule (11) and a retaining ring (10) are provided between the limiting pressure cap (6) and the compression spring (7). The capsule (11) is located on one side of the limiting pressure cap (6). A steel pipe (12) is fixedly connected to the outside of the capsule (11) by vulcanization. A through hole (601) is opened on the limiting pressure cap (6). The steel pipe (12) passes through the through hole (601) and extends out of the limiting pressure cap (6) before being connected to a needle bypass valve (13) and a one-way valve (14). The capsule (11) is filled with hydraulic oil.

3. The tight oil and gas CO2 huff and puff flow self-regulating injection pump according to claim 1, characterized in that: Hydraulic oil is filled in the space formed by the right end of the floating piston (8), the front plunger (1), and the rear plunger (2), so that the floating piston (8) is located in the middle of the central hole (104).

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