Annular injection paraffin control device and paraffin control method

Abstract

The invention provides an annulus injection paraffin control device and a paraffin control method.The annulus injection paraffin control device comprises a paraffin removal and control well completion pipe string arranged in a casing annulus, the paraffin removal and control well completion pipe string is communicated with a ground injection device, a paraffin removal and control agent injection valve is connected to the paraffin removal and control well completion pipe string and comprises a check valve and a counterbalance valve which are oppositely arranged, and the check valve is communicated with the counterbalance valve. An inlet of the paraffin removal and inhibition agent injection valve is formed in one side of the back pressure valve and communicated with the annulus, and an outlet of the paraffin removal and inhibition agent injection valve is formed in one side of the check valve and communicated with the oil pipe. The well completion pipe string with the paraffin removal and inhibition agent injection valve is tripped into an original well, a paraffin removal and inhibition agent injection channel is an annular space between an oil pipe and a casing pipe, the problems that the friction resistance is large, the starting pressure is high and the operation load is high when a capillary pump injects the paraffin removal and inhibition agent are solved, oil pipe perforation is not carried out, the well completion pipe string structure is intact, and the service life of the well completion pipe string is prolonged. Well integrity issues with failure of the first barrier are addressed.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development technology, and particularly relates to the field of wax prevention and control technology for condensate oil and gas reservoirs, specifically to annular injection wax prevention device and wax prevention method. Background Technology

[0002] Condensate gas reservoirs are a unique and complex type of gas reservoir characterized by high pressure and high wax content. The study of paraffin deposition is a major challenge in the exploitation of high-temperature, high-pressure, deep condensate gas reservoirs. In actual production, with the occurrence of wax deposition in different oil and gas fields, many wax removal and prevention technologies have been practically applied in the field.

[0003] Currently, chemical wax removal and prevention technologies are widely used, including: Technology 1: using an externally fixed capillary tube and chemical injection valve to inject wax-removing agents via a surface chemical injection system; Technology 2: injecting wax-removing agents into the annulus after tubing perforation. However, with actual production, Technology 1 has revealed some challenging problems: ① The small capillary inner diameter results in high pump friction and high starting pressure, keeping the injection system under constant high load, affecting long-term serviceability; ② The injection rate is limited by the capillary inner diameter and pump pressure, resulting in a relatively small pump rate, ranging from 0 to 45 L / h, which is insufficient to address severe wax blockage in the wellbore. Similarly, Technology 2 also suffers from well integrity issues due to the failure of the first barrier after tubing perforation. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an annular injection anti-wax device and method. By running a completion string with an anti-wax agent injection valve into the original well, the anti-wax agent injection channel is the annulus between the tubing and the casing. This solves the problems of high friction, high starting pressure, and high operating load when injecting anti-wax agent by capillary pump. Furthermore, this invention does not involve tubing perforation, and the completion string structure remains intact, thus solving the well integrity problem caused by the failure of the first barrier.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an annular injection anti-wax device, comprising a wax-removing and anti-wax completion string disposed in the casing annulus, the wax-removing and anti-wax completion string being connected to a surface injection device, a wax-removing and anti-wax agent injection valve being connected to the wax-removing and anti-wax agent injection string, the wax-removing and anti-wax agent injection valve comprising a check valve and a back pressure valve arranged in opposite directions, the inlet of the wax-removing and anti-wax agent injection valve being disposed on one side of the back pressure valve and communicating with the annulus, and the outlet of the wax-removing and anti-wax agent injection valve being disposed on one side of the check valve and communicating with the tubing.

[0006] Furthermore, the surface injection device includes dedicated pumping equipment and pump truck equipment. The dedicated pumping equipment is used for continuous injection under normal operating conditions, while the pump truck equipment is used for wellbore protection when large-volume pumping is required to deblock, clean, and prevent waxing, or when the well is shut down and reopened for a long period of time.

[0007] Furthermore, the dedicated pumping equipment uses a pneumatic booster pump with a displacement range of 0–100 L / h; the pump truck equipment has a displacement range of 0–600 L / h.

[0008] Furthermore, the dewaxing and anti-wax completion string includes a tubing hanger, a downhole safety valve, and tubing connected in sequence, with the dewaxing and anti-wax injection valve connected to the tubing and located in the annulus.

[0009] Furthermore, the wax removal and anti-wax injection valve mainly consists of a check valve and a back pressure valve arranged in opposite directions. The back pressure valve and the check valve share the same valve seat, with the back pressure valve on the upper side of the valve seat and the check valve on the lower side of the valve seat.

[0010] Furthermore, the back pressure valve includes an inflation chamber, a back pressure valve compression spring, a back pressure valve ball, and a valve seat. The back pressure valve ball is connected to the back pressure valve compression spring, and under the pressure of the inflation chamber and the back pressure valve compression spring, the back pressure valve ball abuts against the upper part of the valve seat from top to bottom.

[0011] Furthermore, the check valve includes a check valve ball, a check valve compression spring, and a valve seat. The check valve ball is connected to the check valve compression spring, and the check valve compression spring pushes the check valve ball against the lower part of the valve seat from bottom to top.

[0012] Furthermore, the valve ball and the top part of the valve seat of the check valve and the back pressure valve have a conical wedge structure.

[0013] Furthermore, the gas filling the chamber is hydrogen or helium.

[0014] This invention also provides a method for preventing wax accumulation in high-wax gas wells, employing the aforementioned annular injection anti-wax device, with the specific steps as follows:

[0015] S1 runs the wax removal and prevention completion string into the oil well. At this time, the annular pressure outside the wax removal and prevention agent injection valve is P1, the back pressure valve is set to P2, and the oil pressure at the wax removal and prevention agent injection valve position is P3.

[0016] The S2 ground injection device injects anti-wax agent into the annular pump, increasing the annular pressure outside the anti-wax agent injection valve to P1. When the back pressure valve reaches the set pressure P2, the back pressure valve opens. When P1 is greater than the oil pressure P3 at the anti-wax agent injection valve position, the check valve opens, and at this time, the annular protective fluid above the anti-wax agent injection valve position enters the oil pipe.

[0017] When the dewaxing agent completely fills the annulus above the dewaxing agent injection valve (S3), the conditions for annulus injection are met, thus achieving the purpose of dewaxing.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] This invention discloses an annular injection anti-wax device, which connects an anti-wax injection valve to the anti-wax completion string. The annulus between the anti-wax completion string and the casing serves as the anti-wax injection channel. The diameter of this injection channel is 170-220mm, which is larger than the 4.7mm diameter of the capillary tube. This solves the problems of high friction, high starting pressure, and high operating load when injecting anti-wax agents using capillary pumps. Furthermore, because this invention uses an anti-wax injection valve, the opening and closing of the flow valve and back pressure valve are achieved through pressure changes, thereby injecting anti-wax agents into the anti-wax completion string. Therefore, the anti-wax completion string of this invention does not require tubing perforation, and the completion string structure remains intact, solving the well integrity problem caused by the failure of the first barrier.

[0020] The surface injection device in this invention uses specialized pumping equipment and pump trucks, enabling continuous or intermittent pumping, which facilitates production management. Compared to conventional chemical injection valve systems, this device employs an annular injection method, resulting in lower pumping friction, lower starting pressure, and larger injection volume. In long-term service, it minimizes the overall system load, extends the system's operating cycle, and increases system safety. Furthermore, the specialized pumping equipment and pump trucks inject anti-wax agents, achieving a larger injection volume of 0-600 L / h, which can solve the problem of severe wax blockage in wellbores. Attached Figure Description

[0021] Figure 1 The process of injecting anti-wax agent into the annulus;

[0022] Figure 2 For the wax removal and anti-wax injection valve;

[0023] Figure 3 To remove the wax-resistant completion string during well entry;

[0024] Figure 4 This is the state when the anti-wax agent injection valve is open;

[0025] Figure 5 Process for injecting dewaxing agent into the annulus of the pump truck;

[0026] Figure 6 Process for injecting anti-wax agent into the annulus of a dedicated pumping equipment;

[0027] In the attached diagram: 1. Special pumping equipment; 2. Pump truck equipment; 3. Wellhead production tree; 4. Tubing hanger; 5. Downhole safety valve; 6. Tubing; 7. Wax removal and anti-wax injection valve; 8. Wax removal and anti-wax agent; 9. Annular protective fluid; 10. Packer; 11. Oil and gas layer; 71. Gas filling chamber; 72. Back pressure valve compression spring; 73. Back pressure valve ball; 74. Check valve ball; 75. Check valve compression spring; 76. Back pressure valve; 77. Check valve. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] The present invention provides an annular injection anti-wax device, the structure of which mainly includes a surface injection device, a wax removal and anti-wax completion string, a wax removal and anti-wax injection valve 7, and a packer 10, wherein:

[0030] The surface injection device includes a dedicated pumping equipment 1 and a pump truck equipment 2. The dedicated pumping equipment 1 is mainly used for continuous injection under normal working conditions, while the pump truck equipment 2 is mainly used for wellbore protection when large-volume pumping is required to de-block, clean, and prevent waxing, or when the well is shut down and reopened for a long time.

[0031] The dedicated injection pump unit 1 consists of a chemical injection pump, a surface check valve, and injection pipelines. The chemical injection pump is driven by a pneumatic booster pump, and its output pressure and flow rate can be adjusted in real time according to operating conditions, enabling programmed injection under high-pressure conditions. The surface check valve isolates pressure leakage during injection, ensuring well control safety at the wellhead. The dedicated injection pump unit 1 is mainly used for continuous wax-prevention injection under normal operating conditions, with a displacement range of 0–100 L / h.

[0032] The pump truck injection device 2 consists of a pump truck and connecting pipelines. Its pump outlet pipeline is connected to the left flange of the wellhead and is controlled by a stopcock and a flat valve. The discharge range is 0-600L / h. It is mainly used for wellbore protection work when a large-volume pump injection is needed to remove wax blockage or when the well is shut down and reopened for a long time. It is used to quickly solve the wax blockage situation in the wellbore.

[0033] The wax removal and prevention completion string includes a tubing hanger 4, a downhole safety valve 5, and tubing 6 connected in sequence. The inlet of tubing 6 extends into the oil and gas layer 11, and the oil and gas layer 11 is separated from the annulus by a packer 10. The wax removal and prevention agent injection valve 7 is connected to the part of tubing 6 located in the annulus. The wax removal and prevention agent injection valve 7 is mainly composed of a one-way valve 77 and a back pressure valve 76 arranged in opposite directions. The inlet of the wax removal and prevention agent injection valve 7 is located on the side of the back pressure valve 76 and communicates with the annulus. The outlet of the wax removal and prevention agent injection valve 7 is located on the side of the one-way valve 77 and communicates with the tubing. The wax removal and prevention agent injection valve 7 provides an injection channel for the wax removal and prevention agent to achieve the purpose of wax removal and prevention. The function of the one-way valve 77 is to ensure that the wax removal and prevention agent passes through the annulus in one direction and prevent oil and gas in the tubing from flowing back into the annulus.

[0034] Among them, such as Figure 2As shown, the back pressure valve 76 is composed of an inflation chamber 71, a back pressure valve compression spring 72, a back pressure valve ball 73, and a valve seat. The inflation chamber 71 is used for pre-pressurization and setting the pressure opening value. The check valve 77 is composed of a check valve ball 74, a check valve compression spring 75, and a valve seat. The back pressure valve 76 and the check valve 77 share the same valve seat. The back pressure valve 76 is on the upper side of the valve seat, and the check valve 77 is on the lower side. The back pressure valve ball 73 is connected to the back pressure valve compression spring 72 and, under the pressure of the inflation chamber 71, it abuts against the upper part of the valve seat from top to bottom. The check valve ball 74 is connected to the check valve compression spring 75, and the check valve compression spring 75 abuts against the lower part of the valve seat from bottom to top.

[0035] When the pressure in the annulus is P1, the pressure opening value of the back pressure valve 76 is P2, and the pressure in the oil pipe is P3:

[0036] When the pressure in the back pressure valve 76 is less than the opening pressure P2, the back pressure valve spring 72 is compressed and the back pressure valve ball 73 and valve seat are in a closed state.

[0037] When the annular pressure P1 reaches the set opening pressure value P2, the back pressure valve 76 opens and the back pressure valve ball 73 leaves the valve seat.

[0038] When the annular pressure P1 is greater than the oil pipe pressure P3, the check valve 77 opens, and the dewaxing agent enters the oil pipe through the back pressure valve 76 and the check valve 77, thus playing the role of dewaxing.

[0039] Preferably, the valve ball and valve seat top contact portion of the back pressure valve 76 and the one-way valve 77 are of a conical wedge surface structure, which can effectively ensure the tightness during low-displacement pumping.

[0040] Preferably, the gas in the filling chamber 71 can be hydrogen or helium.

[0041] Preferably, all well-drilling tools are made of corrosion-resistant alloys, which can effectively ensure the long-term stability of the tool string under high temperature, high pressure and corrosion conditions.

[0042] like Figure 1 As shown, this embodiment provides a method for operating an annular injection anti-wax device, the method comprising:

[0043] (1) A dewaxing and anti-wax completion string is run into the oil well. The dewaxing and anti-wax completion string comprises, from top to bottom, a tubing hanger 4, a downhole safety valve 5, tubing 6, a dewaxing and anti-wax injection valve 7, and a packer 10, all connected by threads. The wellbore condition at this time is as follows: Figure 3 As shown.

[0044] (2) The dewaxing agent is injected into the annular space using a pump truck and dedicated pumping equipment. At this time, the annular pressure outside the dewaxing agent injection valve is P1, the set pressure of the back pressure valve's charging chamber is P2, and the oil pressure at the dewaxing agent injection valve position is P3. The pump is started, and the annular pressure P1 outside the dewaxing agent injection valve continuously rises. When it reaches the set pressure P2 of the back pressure valve's charging chamber, the back pressure valve opens. When P1 is greater than the oil pressure P3 at the dewaxing agent injection valve position, the check valve opens. Figure 4 As shown. At this point, the annular protective fluid above position 7 of the anti-wax agent injection valve begins to enter the oil pipe until the anti-wax agent completely fills the annulus above position 7. At this point, the conditions for annular injection are met, thereby achieving the purpose of anti-wax agent removal.

[0045] (3) Intermittent pumping for dewaxing. When a high-wax-content well is shut down and reopened after a long period of time, a large-volume pumping of dewaxing agent is required. A pump truck is used to inject the dewaxing agent at a large volume to restore wellbore patency. Figure 5 As shown.

[0046] (4) Continuous pumping for wax prevention. When a low-temperature, low-yield, high-wax-content well is in normal production, continuous pumping of wax inhibitor with a small displacement is required. Specialized pumping equipment is used to continuously pump the wax inhibitor at a small displacement to ensure unobstructed wellbore flow. Figure 6 As shown.

Claims

1. An annular injection anti-wax device, characterized in that, The system includes a wax removal and prevention completion string installed in the casing annulus. The wax removal and prevention completion string is connected to the surface injection device. A wax removal and prevention agent injection valve (7) is connected to the wax removal and prevention completion string. The wax removal and prevention agent injection valve (7) includes a one-way valve (77) and a back pressure valve (76) arranged in opposite directions. The inlet of the wax removal and prevention agent injection valve (7) is located on the side of the back pressure valve (76) and is connected to the annulus. The outlet of the wax removal and prevention agent injection valve (7) is located on the side of the one-way valve (77) and is connected to the tubing.

2. The annular injection anti-wax device according to claim 1, characterized in that, The surface injection device includes a dedicated pump injection device (1) and a pump truck device (2). The dedicated pump injection device (1) is used for continuous injection under normal working conditions, and the pump truck device (2) is used for wellbore protection when large-volume pump injection is required to de-clog, clean, and prevent waxing, or when the well is shut down and reopened for a long time.

3. The annular injection anti-wax device according to claim 1, characterized in that, The special pumping equipment (1) uses a pneumatic booster pump with a displacement range of 0 to 100 L / h; the pump truck equipment (2) has a displacement range of 0 to 600 L / h.

4. The annular injection anti-wax device according to claim 1, characterized in that, The dewaxing and anti-wax completion string includes a tubing hanger (4), a downhole safety valve (5), and tubing (6) connected in sequence. The dewaxing and anti-wax injection valve (7) is connected to the tubing (6) and located in the annulus.

5. The annular injection anti-wax device according to claim 1, characterized in that, The anti-wax agent injection valve (7) is mainly composed of a one-way valve (77) and a back pressure valve (76) arranged in opposite directions. The back pressure valve (76) and the one-way valve (77) share the same valve seat. The back pressure valve (76) is on the upper side of the valve seat, and the one-way valve (77) is on the lower side of the valve seat.

6. The annular injection anti-wax device according to claim 5, characterized in that, The back pressure valve (76) includes an inflation chamber (71), a back pressure valve compression spring (72), a back pressure valve ball (73), and a valve seat. The back pressure valve ball (73) is connected to the back pressure valve compression spring (72). Under the pressure of the inflation chamber (71) and the back pressure valve compression spring (72), the back pressure valve ball (73) abuts against the upper part of the valve seat from top to bottom.

7. The annular injection anti-wax device according to claim 5, characterized in that, The check valve (77) includes a check valve ball (74), a check valve compression spring (75), and a valve seat. The check valve ball (74) is connected to the check valve compression spring (75), and the check valve compression spring (75) pushes the check valve ball (74) against the lower part of the valve seat from bottom to top.

8. The annular injection anti-wax device according to claim 5, characterized in that, The valve ball and valve seat top part of the one-way valve (77) and back pressure valve (76) have a conical wedge surface structure.

9. The annular injection anti-wax device according to claim 6, characterized in that, The gas in the filling chamber (71) is hydrogen or helium.

10. A method for preventing wax deposition in high-wax gas wells, characterized in that, The specific steps of using the annular injection anti-wax device according to any one of claims 1 to 9 are as follows: S1 sends a clean and anti-wax completion string into the oil well. At this time, the annular pressure of the clean and anti-wax injection valve (7) is P1, the back pressure valve is set to P2, and the oil pressure at the position of the clean and anti-wax injection valve (7) is P3. The S2 ground injection device injects anti-wax agent into the annular pump, increasing the annular pressure outside the anti-wax agent injection valve (7) to P1. When the back pressure valve set pressure P2 is reached, the back pressure valve (76) opens. When P1 is greater than the oil pressure P3 at the anti-wax agent injection valve position, the check valve (77) opens, and at this time, the annular protective fluid above the position of the anti-wax agent injection valve (7) enters the oil pipe. When the anti-wax agent completely fills the annulus above the anti-wax agent injection valve (7), the conditions for annulus injection are met, thereby achieving the purpose of anti-wax agent removal.

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