A method for applying a corrosion-resistant coating to a downhole casing of an oil or gas well

Abstract

This invention relates to a construction device and method for applying an anti-corrosion coating to downhole casing in oil and gas wells, specifically relating to such a device and method. The device includes a tool string body, with a safety connector connected to one end and a retrieval bridge plug at the other end. The retrieval bridge plug is connected to the tool string body via an electric pin. The invention is characterized by the inclusion of a primer spraying device, a topcoat spraying device, a surface treatment device, and a heating device on the tool string body between the safety connector and the retrieval bridge plug. This invention addresses the application of an anti-corrosion coating to oil and gas well casings that have been cemented downhole and are in service. Compared to the current method of periodic chemical addition for corrosion protection, this method offers lower labor intensity, greater operability, faster formation of the anti-blowout coating, stronger resistance, lower cost, and better anti-corrosion effect.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well development technology, and specifically to a method for constructing an anti-corrosion coating for downhole casing in oil and gas wells. Background Technology

[0002] During service, oil and gas well casings are exposed to formation water, acidic gases, or corrosive fluids for extended periods, making them prone to corrosion, cracking, and perforation, all of which threaten wellbore safety. Recent CO2 flooding technology has exacerbated this problem. While CO2 flooding is a crucial CCUS (CO2 capture, utilization, and storage) technology in oilfields, many injection and production well casings in CO2 injection projects were installed without proper corrosion protection in high-concentration CO2 environments, leading to severe CO2 corrosion. Common corrosion protection methods involve periodically adding corrosion inhibitors to the wellbore. While this slows the corrosion rate, it requires frequent, labor-intensive, and costly applications. Furthermore, because the casings in injection and production wells are cemented into the wellbore, and the complex environment of oil and gas wells (high temperature, high pressure, liquids, and gases) makes casing spraying for corrosion protection extremely difficult, there are currently no reports on suitable materials, tools, or construction methods.

[0003] Currently, the anti-corrosion coating materials, tools, and construction methods for production casing are relatively mature. However, they are generally limited to the casing production stage. Once the production casing has been installed and cemented into the wellbore, the existing anti-corrosion spraying methods cannot be applied. In some oil and gas wells, the production casing has not been treated for CO2 corrosion in the cemented state. However, the production casing must be used in a high-concentration CO2 environment for a long time. The problem of how to directly apply anti-corrosion coatings to oil and gas well casings in complex downhole environments urgently needs to be solved. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for rapidly spraying an anti-corrosion coating onto the inner surface of oil and gas well casing during its service life using existing tools and forming a spraying tool string. This method is simple to implement, has high coating efficiency, fast coating adhesion, high strength, strong corrosion resistance, long effective period, and minimal environmental pollution during construction.

[0005] This invention discloses a construction device for anti-corrosion coating of downhole casing in oil and gas wells, comprising a tool string body, a safety joint connected to one end of the tool string body, and a retrieval bridge plug provided at the other end of the tool string body, the retrieval bridge plug being connected to the tool string body via an electric pin; a primer spraying device, a topcoat spraying device, a surface treatment device, and a heating device are provided on the tool string body between the safety joint and the retrieval bridge plug.

[0006] The primer spraying device, topcoat spraying device, surface treatment device, and heating device are all connected to the power supply via cables; the primer spraying device, topcoat spraying device, and surface treatment device are respectively connected to the power supply and supply system via cables and pipeline systems.

[0007] The tool string body is provided with primer spray holes, topcoat spray holes and abrasive spray holes at the positions corresponding to the primer spraying device, topcoat spraying device and surface treatment device, respectively. The primer spraying device, topcoat spraying device and surface treatment device spray out the coating material through the primer spray holes, topcoat spray holes and abrasive spray holes, respectively.

[0008] The tool string body has a safety connector at one end, which is also connected to a centralizer.

[0009] Preferably, the heating device includes an upper heating device and a lower heating device, and the upper heating device is provided on the tool string body between the primer spraying device and the topcoat spraying device;

[0010] The lower heating device is provided on the tool string body between the topcoat spraying device and the surface treatment device;

[0011] Both the upper heating device and the lower heating device are connected to a power source via cables.

[0012] Preferably, the heating device is an electric heating mantle.

[0013] Preferably, the topcoat spraying device is a pneumatic airless sprayer.

[0014] Preferably, the primer spraying device is a Reactor hydraulic two-component sprayer.

[0015] Preferably, the surface treatment device is a suction-type dry sandblasting machine.

[0016] Preferably, there are two primer spray holes, two topcoat spray holes, and two abrasive spray holes; the two primer spray holes, two topcoat spray holes, and two abrasive spray holes are symmetrically arranged on the corresponding sides of the corresponding positions on the tool string body.

[0017] A method for applying an anti-corrosion coating to downhole casing of oil and gas wells, using an application device for applying the anti-corrosion coating to downhole casing of oil and gas wells, includes the following steps:

[0018] Step 1: Use a scraper and gauge of appropriate size to treat the entire wellbore of the target oil and gas well to remove burrs from the inner wall of the wellbore casing and ensure normal tool tripping operations.

[0019] Step 2: Full wellbore washing to remove dirt and sludge from the inner wall of the wellbore casing;

[0020] Step 3: Connect the power supply system to the tool string body via cables and pipelines, and lower it into the well casing of the oil and gas well via pulleys.

[0021] Step 4: Install the safety connector on top of the tool string body to ensure that the tool string body can be disconnected from the cable and pipeline system in the event of abnormal jamming.

[0022] Step 5: Then install a centralizer on the upper part of the tool string body. Its function is to keep the entire tool string body in the center position in the wellbore.

[0023] Step 6: As the tool string body descends from the wellhead to the bottom of the well, the surface treatment device at the bottom of the tool string body sprays a foam system mixed with abrasives from the ground through abrasive nozzles onto the inner wall of the casing to grind and roughen the inner wall of the casing, thereby increasing the surface area of ​​the inner wall of the casing.

[0024] Step 7: During the downward movement of the tool string body, the upper heating device and the lower heating device are turned on simultaneously to dry the inner surface of the sleeve.

[0025] Step 8: When the tool string body reaches the designed bottom position, the surface treatment device stops working, the ground operation triggers the electric pin, the bridge plug seat can be retrieved and sealed to the designated position, and disengaged from the electric pin.

[0026] Step 9: The tool string body begins to ascend from the bottom of the well. The primer spraying device starts to work. The power supply system sprays the primer evenly onto the inner wall of the casing through the primer spray holes via the cables and pipelines in the pipeline system. The upper heating device dries the primer in time.

[0027] Step 10: During the upward movement of the tool string body, the topcoat spraying system is also started. The ground supply system sprays the topcoat evenly onto the inner wall of the casing through the topcoat spray nozzles. The lower heating device dries the topcoat in time, so that the anti-corrosion coating can quickly form a stable protective layer on the inner wall of the casing.

[0028] Step 11: After the tool string body is removed from the target oil and gas well casing, the retrieval tool for the retrieval bridge plug is lowered to retrieve the bridge plug, thus keeping the production casing of the target oil and gas well casing unobstructed.

[0029] Step 12: The oil and gas wells resume normal production operations and the construction of the carbon dioxide corrosion prevention coating on the downhole casing of the oil and gas wells is completed.

[0030] This invention relates to a method for applying an anti-corrosion coating to oil and gas well casings that have been cemented downhole and are in service. Compared to the current method of periodically adding chemicals for corrosion protection, this method has lower labor intensity, higher operability, faster formation of the blowout preventer coating, stronger resistance, lower cost, and better anti-corrosion effect.

[0031] This invention enables direct and rapid anti-corrosion spraying of oil and gas well production casing during its service life, i.e., when it is cemented downhole, thereby improving the anti-corrosion capability of oil and gas well casing in high concentrations of CO2 and extending the service life of the casing. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the toolchain body of the present invention.

[0033] Reference numerals: 1-Power supply system, 2-Cable and pipeline system, 3-Pulley, 4-Safety joint, 5-Center, 6-Primer spraying device, 7-Primer nozzle, 8-Upper heating device, 9-Topcoat spraying device, 10-Topcoat nozzle, 11-Lower heating device, 12-Surface treatment device, 13-Abrasive nozzle, 14-Electric pin, 15-Retrievable bridge plug, 16-Well casing. Detailed Implementation

[0034] The present invention provides a construction device for anti-corrosion coating of downhole casing in oil and gas wells, comprising a tool string body, a safety connector 4 connected to one end of the tool string body, and a retrieval bridge plug 15 provided on the other end of the tool string body, the retrieval bridge plug 15 being connected to the tool string body via an electric pin 14.

[0035] The tool string body between the safety connector 4 and the retrievable bridge plug 15 is equipped with a primer spraying device 6, a topcoat spraying device 9, a surface treatment device 12, and a heating device.

[0036] The primer spraying device 6, topcoat spraying device 9, surface treatment device 12, and heating device are all connected to the power supply via cables; the primer spraying device 6, topcoat spraying device 9, and surface treatment device 12 are respectively connected to the power supply and supply system 1 via cables and pipeline system 2; the pipeline system and supply system are used to supply sprayed materials to the primer spraying device 6, topcoat spraying device 9, and surface treatment device 12.

[0037] The tool string body is provided with primer spraying device 6, topcoat spraying device 9, and surface treatment device 12, respectively, and primer spraying hole 7, topcoat spraying hole 10, and abrasive spraying hole 13. The primer spraying device 6, topcoat spraying device 9, and surface treatment device 12 spray out the coating material through the primer spraying hole 7, topcoat spraying hole 10, and abrasive spraying hole 13, respectively.

[0038] The tool string body is equipped with a safety connector 4 and a straightener 5 is also connected to one end.

[0039] In one embodiment, the heating device includes an upper heating device 8 and a lower heating device 11, and the upper heating device 8 is provided on the tool string body between the primer spraying device 6 and the topcoat spraying device 9.

[0040] The lower heating device 11 is provided on the tool string body between the topcoat spraying device 9 and the surface treatment device 12;

[0041] Both the upper heating device 8 and the lower heating device 11 are connected to a power source via cables.

[0042] In one embodiment, the heating device is an electric heating mantle.

[0043] In one embodiment, the topcoat spraying device 9 is a pneumatic airless sprayer, specifically the GPQ9CA pneumatic airless sprayer manufactured by Tianjin Binhai New Area Tanggu Yihui Sandblasting and Spraying Equipment Co., Ltd. The pneumatic airless sprayer relies on compressed air from the air compressor of the supply system for power to spray the topcoat. The supply system is a device in the prior art that supplies topcoat to the pneumatic airless sprayer.

[0044] In one embodiment, the primer spraying device 6 is a Reactor hydraulic two-component sprayer, specifically the Reactor hydraulic two-component sprayer H-XP3, manufactured by Graco Inc. The Reactor hydraulic two-component sprayer relies on the power provided by compressed air compressed by an air compressor in the supply system to spray out the primer. The supply system is a device that supplies primer to the hydraulic two-component sprayer in the prior art.

[0045] In one embodiment, the surface treatment device 12 is a suction-type dry sandblasting machine, specifically a GS-0722 type oil pipe special suction-type dry sandblasting machine manufactured by Beijing Huizhi Tongchuang Technology Development Co., Ltd. The suction-type dry sandblasting machine relies on compressed air in the air compressor of the supply system to provide power for ejection. The supply system is a device that supplies abrasive to the suction-type dry sandblasting machine in the prior art.

[0046] In one embodiment, there are two primer spray holes 7, two topcoat spray holes 10, and two abrasive spray holes 13; the two primer spray holes 7, the two topcoat spray holes 10, and the two abrasive spray holes 13 are symmetrically arranged on the corresponding sides of the corresponding positions of the tool string body.

[0047] A method for applying an anti-corrosion coating to downhole casing of oil and gas wells, using an application device for applying the anti-corrosion coating to downhole casing of oil and gas wells, includes the following steps:

[0048] Step 1: Use a scraper and gauge of appropriate size to treat the entire wellbore of the target oil and gas well to remove burrs from the inner wall of the well casing 16 and ensure normal tool tripping operations.

[0049] Step 2: Full wellbore washing to remove dirt, sludge, and other debris from the inner wall of the well casing 16;

[0050] Step 3: Connect the power supply system 1 to the tool string body through the cable and pipeline system 2, and lower it into the well casing 16 of the oil and gas well through the pulley 3.

[0051] Step 4: Install safety connector 4 on top of the tool string body to ensure that the tool string body can be disconnected from the cable and pipeline system 2 in case of abnormal jamming of the drill bit.

[0052] Step 5: Then install the centralizer 5 on the upper part of the tool string body. Its function is to keep the entire tool string body in the center position in the wellbore.

[0053] Step 6: As the tool string body descends from the wellhead to the bottom of the well, the surface treatment device 12 at the bottom of the tool string body sprays the foam system mixed with abrasive on the ground through the abrasive spray hole 13 onto the inner wall of the casing to grind and roughen the inner wall of the casing and increase the surface area of ​​the inner wall of the casing.

[0054] Step 7: During the downward movement of the tool string body, the upper heating device 8 and the lower heating device 11 are turned on simultaneously to dry the inner surface of the sleeve.

[0055] Step 8: When the tool string body reaches the designed bottom position, the surface treatment device 12 stops working, the ground operation triggers the electric pin 14, the retrievable bridge plug 15 is seated in the designated position and disengaged from the electric pin 14.

[0056] Step 9: The tool string body begins to move upward from the bottom of the well. The primer spraying device 6 starts to work. The power supply system 1 sprays the primer evenly onto the inner wall of the casing through the pipeline in the cable and pipeline system 2. The upper heating device 8 dries the primer in time.

[0057] Step 10: During the upward movement of the tool string body, the topcoat spraying system is also started. The ground supply system sprays the topcoat evenly onto the inner wall of the casing through the topcoat spray nozzle 10. The lower heating device 11 dries the topcoat in time, so that the anti-corrosion coating can quickly form a stable protective layer on the inner wall of the casing.

[0058] Step 11: After the tool string body is removed from the target oil and gas well casing, the matching retrieval tool for the retrieval bridge plug 15 is lowered to retrieve the bridge plug, so that the production casing of the target oil and gas well casing remains unobstructed.

[0059] Step 12: The oil and gas wells resume normal production operations and the construction of the carbon dioxide corrosion prevention coating on the downhole casing of the oil and gas wells is completed.

[0060] This invention relates to a method for applying an anti-corrosion coating to oil and gas well casings that have been cemented downhole and are in service. Compared to the current method of periodically adding chemicals for corrosion protection, this method has lower labor intensity, higher operability, faster formation of the blowout preventer coating, stronger resistance, lower cost, and better anti-corrosion effect.

Claims

1. A method for applying an anti-corrosion coating to downhole casing of an oil and gas well, using an application device for applying the anti-corrosion coating to downhole casing of an oil and gas well; The construction device for anti-corrosion coating of downhole casing in oil and gas wells includes a tool string body. A safety joint is connected to one end of the tool string body, and a retrieval bridge plug is provided at the other end of the tool string body. The retrieval bridge plug is connected to the tool string body by an electric pin. A primer spraying device, a topcoat spraying device, a surface treatment device, and a heating device are provided on the tool string body between the safety joint and the retrieval bridge plug. The primer spraying device, topcoat spraying device, surface treatment device, and heating device are all connected to the power supply via cables; the primer spraying device, topcoat spraying device, and surface treatment device are respectively connected to the power supply and supply system via cables and pipeline systems. The tool string body is provided with primer spray holes, topcoat spray holes and abrasive spray holes at the positions corresponding to the primer spraying device, topcoat spraying device and surface treatment device, respectively. The primer spraying device, topcoat spraying device and surface treatment device spray out the coating material through the primer spray holes, topcoat spray holes and abrasive spray holes, respectively. A stabilizer is also connected to one end of the tool string body with a safety connector; The heating device includes an upper heating device and a lower heating device, and the upper heating device is provided on the tool string body between the primer spraying device and the topcoat spraying device; The lower heating device is provided on the tool string body between the topcoat spraying device and the surface treatment device; Both the upper heating device and the lower heating device are connected to a power source via cables; The construction method includes the following steps: Step 1: Use a scraper and gauge of appropriate size to treat the entire wellbore of the target oil and gas well to remove burrs from the inner wall of the wellbore casing and ensure normal tool tripping operations. Step 2: Full wellbore washing to remove dirt and sludge from the inner wall of the wellbore casing; Step 3: Connect the power supply system to the tool string body via cables and pipelines, and lower it into the well casing of the oil and gas well via pulleys. Step 4: Install the safety connector on top of the tool string body to ensure that the tool string body can be disconnected from the cable and pipeline system in the event of abnormal jamming. Step 5: Then install a centralizer on the upper part of the tool string body. Its function is to keep the entire tool string body in the center position in the wellbore. Step 6: As the tool string body descends from the wellhead to the bottom of the well, the surface treatment device at the bottom of the tool string body sprays a foam system mixed with abrasives from the ground through abrasive nozzles onto the inner wall of the casing to grind and roughen the inner wall of the casing, thereby increasing the surface area of ​​the inner wall of the casing. Step 7: During the downward movement of the tool string body, the upper heating device and the lower heating device are turned on simultaneously to dry the inner surface of the sleeve. Step 8: When the tool string body reaches the designed bottom position, the surface treatment device stops working, the ground operation triggers the electric pin, the bridge plug seat can be retrieved and sealed to the designated position, and disengaged from the electric pin. Step 9: The tool string body begins to ascend from the bottom of the well. The primer spraying device starts to work. The power supply system sprays the primer evenly onto the inner wall of the casing through the primer spray holes via the cables and pipelines in the pipeline system. The upper heating device dries the primer in time. Step 10: During the upward movement of the tool string body, the topcoat spraying system is also started. The ground supply system sprays the topcoat evenly onto the inner wall of the casing through the topcoat spray nozzles. The lower heating device dries the topcoat in time, so that the anti-corrosion coating can quickly form a stable protective layer on the inner wall of the casing. Step 11: After the tool string body is removed from the target oil and gas well casing, the retrieval tool for the retrieval bridge plug is lowered to retrieve the bridge plug, thus keeping the production casing of the target oil and gas well casing unobstructed. Step 12: The oil and gas wells resume normal production operations and the construction of the carbon dioxide corrosion prevention coating on the downhole casing of the oil and gas wells is completed.

2. The method of claim 1, wherein the method further comprises the step of: The heating device is an electric heating jacket.

3. The construction method of the anti-corrosion coating for downhole casing of oil and gas wells as described in claim 1, characterized in that, The topcoat spraying device is a pneumatic airless sprayer.

4. The construction method of the anti-corrosion coating for downhole casing of oil and gas wells as described in claim 1, characterized in that, The primer spraying device is a Reactor hydraulic two-component sprayer.

5. The construction method of the anti-corrosion coating for downhole casing of oil and gas wells as described in claim 1, characterized in that, The surface treatment device is a suction-type dry sandblasting machine.

6. The construction method for the anti-corrosion coating of downhole casing in oil and gas wells as described in claim 1, characterized in that, The primer spray hole, topcoat spray hole and abrasive spray hole are each set to two; the two primer spray holes, two topcoat spray holes and two abrasive spray holes are symmetrically arranged on the corresponding sides of the corresponding positions of the tool string body.

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