Construction device and method for anticorrosive coating of underground casing of oil and gas well

Abstract

The invention relates to the technical field of oil and gas well development, in particular to a construction device and method for an anti-corrosion coating of an oil and gas well downhole casing pipe. The construction device comprises a tool string body, and one end of the tool string body is connected with a safety connector; a fishable bridge plug is arranged at the other end of the tool string body and connected with the tool string body through an electric pin. The tool string is characterized in that a primer spraying device, a finishing paint spraying device, a surface treatment device and a heating device are arranged on the tool string body between the safety joint and the salvageable bridge plug; the anti-corrosion coating construction method is developed for the situation that the oil and gas well casing pipe is sealed underground by cement and the casing pipe is in the service stage, and compared with a regular chemical adding mode adopted for corrosion prevention at present, the anti-corrosion coating construction method is low in labor intensity, high in operability, high in anti-spraying coating forming speed, high in tolerance, low in cost and good in anti-corrosion effect.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well development, and in particular to a construction device and method for an anti-corrosion coating on downhole casing of an oil and gas well. Background Art

[0002] During service, downhole casing in oil and gas wells is susceptible to corrosion, cracks, and perforations, posing risks to wellbore safety due to long-term exposure to formation water, acidic gases, or corrosive fluids. Recent CO2 flooding technology has further exacerbated this corrosion risk. CO2 flooding is a key CO2 capture, utilization, and storage (CCUS) application technology in oilfields. However, many injection and production well casings in CO2 flooding projects are operated without corrosion protection designed for high-concentration CO2 environments. This leads to severe CO2 corrosion in these wells. A common approach to combating casing corrosion is to regularly add an anti-corrosion agent to the wellbore. While this method can slow the corrosion rate, it requires frequent, labor-intensive, and costly additions. Furthermore, since the casing in injection and production wells is already cemented in the wellbore, spraying anti-corrosion coatings is challenging due to the complex downhole environment of high temperatures, high pressures, liquids, and gases. Currently, no relevant reports have been published on materials, tools, or application methods.

[0003] At present, the production casing is relatively mature in terms of anti-corrosion coating materials, tools, and construction methods. However, it is generally limited to the application in the casing production stage. Once the production casing has been installed and sealed in the wellbore with cement, the existing anti-corrosion spraying method cannot be implemented. Existing oil and gas wells are in the cemented state, and the production casing has not been treated with anti-corrosion treatment against CO2 corrosion. However, the production casing must serve in a high-concentration CO2 environment for a long time. How to directly apply anti-corrosion coating to the oil and gas well casing in the complex underground environment needs to be solved urgently. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for rapidly spraying an anti-corrosion coating on the inner surface of an oil and gas well production casing during its service by using existing tools and forming a spray tool string. The method has the advantages of simple construction, high coating operation efficiency, fast coating adhesion speed, high strength, strong corrosion tolerance, long effective period, and low environmental pollution during the construction process. It provides a device and method for constructing an anti-corrosion coating on the downhole casing of an oil and gas well.

[0005] A construction device for an anti-corrosion coating of an underground casing in an oil and gas well, comprising a tool string body. A safety joint is connected to one end of the tool string body, and a retrievable bridge plug is arranged at the other end of the tool string body. The retrievable bridge plug is connected to the tool string body through an electric pin; a primer spraying device, a topcoat spraying device, a surface treatment device and a heating device are arranged on the tool string body between the safety joint and the retrievable bridge plug; The primer spraying device, the topcoat spraying device, the surface treatment device and the heating device are all connected to a power supply through cables; the primer spraying device, the topcoat spraying device and the surface treatment device are respectively connected to the power supply and the supply system through cables and pipeline systems; Primer spray holes, topcoat spray holes and abrasive spray holes are respectively arranged on the tool string body corresponding to the positions of the primer spraying device, the topcoat spraying device and the surface treatment device. The primer spraying device, the topcoat spraying device and the surface treatment device respectively spray spraying materials through the primer spray holes, the topcoat spray holes and the abrasive spray holes; A centralizer is further connected to the end of the tool string where the safety joint is arranged.

[0006] Preferably, the heating device includes an upper heating device and a lower heating device. The upper heating device is arranged on the tool string body between the primer spraying device and the topcoat spraying device; The lower heating device is arranged 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 supply through cables.

[0007] Preferably, the heating device is an electric heating sleeve.

[0008] Preferably, the topcoat spraying device is a pneumatic airless spraying machine.

[0009] Preferably, the primer spraying device is a Reactor hydraulic two-component spraying machine.

[0010] [[ID=**25**]]Preferably, the surface treatment device is a suction type dry sandblasting machine.

[0011] Preferably, the primer spray holes, the topcoat spray holes and the abrasive spray holes are respectively arranged in two; the two primer spray holes, the two topcoat spray holes and the two abrasive spray holes are respectively symmetrically arranged on the corresponding two sides of the corresponding positions of the tool string body.

[0012] A construction method for an anti-corrosion coating of an underground casing in an oil and gas well, using a construction device for an anti-corrosion coating of an underground casing in an oil and gas well, comprising the following steps: Step 1, use a scraper and a drift of appropriate sizes to process the entire wellbore of the target oil and gas well, eliminate burrs on the inner wall of the wellbore casing, and ensure normal tripping operations of subsequent tools; Step 2: Conduct a full wellbore wash to remove dirt, sludge, and other debris from the inner wall of the wellbore casing. Step 3: Connect the power supply and the supply system to the tool string through a cable and pipeline system, and lower it into the casing of the oil and gas wellbore through a pulley. Step 4: Install a safety joint at the top of the tool string body to ensure that when the tool string gets stuck abnormally, the tool string can be disconnected from the cable and pipeline system. Step 5: Then install a centralizer on the upper part of the tool string body, whose function is to keep the entire tool string body centered in the wellbore. Step 6: During the process of the tool string body descending from the wellhead to the bottom of the well, the surface treatment device at the lower part of the tool string body sprays the foam system mixed with abrasives on the inner wall of the casing through the abrasive spray holes, grinds and roughens the inner wall of the casing, and expands the surface area of the inner wall of the casing. Step 7: During the descending process of the tool string, the upper heating device and the lower heating device are turned on simultaneously to dry the inner surface of the casing. Step 8: When the tool string reaches the designed bottom position, the surface treatment device stops working, and the ground operation triggers the electric pin, and the retrievable bridge plug is seated at the designated position and disengages from the electric pin. Step 9: The tool string body starts to ascend from the bottom position, and the primer spraying device starts to work. The power supply and the supply system spray the primer evenly on the inner wall of the casing from the primer spray holes through the pipelines in the cable and pipeline system, and the upper heating device promptly dries the primer. Step 10: During the ascending process of the tool string, the topcoat spraying system also starts. The ground supply system sprays the topcoat evenly on the inner wall of the casing through the topcoat spray holes, and the lower heating device promptly dries the topcoat, enabling the anti-corrosion coating to quickly form a stable protective layer on the inner wall of the casing. Step 11: After the tool string is removed from the entire wellbore of the target oil and gas well, lower the retrieval tool for the retrievable bridge plug to fish out the bridge plug, keeping the production casing of the target oil and gas well fully open. Step 12: Conduct normal production operations on the oil and gas well to complete the construction of the anti-carbon dioxide corrosion coating for the downhole casing of the oil and gas well.

[0013] The present invention is an anti-corrosion coating construction method for oil and gas well casings that have been cemented in the wellbore during their service life. Compared with the current method of adding chemicals regularly for anti-corrosion, this method has low labor intensity, strong operability, a fast anti-spray coating formation speed, strong tolerance, low cost, and good anti-corrosion effect.

[0014] The present invention enables the direct and rapid anti-corrosion spraying construction of production casings in oil and gas wells during their service life, that is, when they are cemented in the wellbore, improves the anti-corrosion ability of oil and gas well casings in high-concentration CO2 environments, and extends the service life of the casings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the tool string body of the present invention.

[0016] Reference numerals: 1 - power supply and supply system, 2 - cable and pipeline system, 3 - pulley, 4 - safety joint, 5 - centralizer, 6 - primer spraying device, 7 - primer spray hole, 8 - upper heating device, 9 - topcoat spraying device, 10 - topcoat spray hole, 11 - lower heating device, 12 - surface treatment device, 13 - abrasive spray hole, 14 - electric pin, 15 - retrievable bridge plug, 16 - wellbore casing. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] A construction device for an anti - corrosion coating of an underground casing in an oil and gas well according to the present invention includes a tool string body. A safety joint 4 is connected to one end of the tool string body, and a retrievable bridge plug 15 is arranged at the other end of the tool string body. The retrievable bridge plug 15 is connected to the tool string body through an electric pin 14; A primer spraying device 6, a topcoat spraying device 9, a surface treatment device 12 and a heating device are arranged on the tool string body between the safety joint 4 and the retrievable bridge plug 15; The primer spraying device 6, the topcoat spraying device 9, the surface treatment device 12 and the heating device are all connected to the power supply through cables; the primer spraying device 6, the topcoat spraying device 9 and the surface treatment device 12 are respectively connected to the power supply and supply system 1 through the cable and pipeline system 2; the pipeline system and the supply system are used to supply ejecta to the primer spraying device 6, the topcoat spraying device 9 and the surface treatment device 12.

[0018] Primer spray holes 7, topcoat spray holes 10 and abrasive spray holes 13 are respectively arranged on the tool string body corresponding to the positions of the primer spraying device 6, the topcoat spraying device 9 and the surface treatment device 12. The primer spraying device 6, the topcoat spraying device 9 and the surface treatment device 12 respectively eject spraying materials through the primer spray holes 7, the topcoat spray holes 10 and the abrasive spray holes 13; A centralizer 5 is further connected to the end of the tool string where the safety joint 4 is arranged.

[0019] In one embodiment, the heating device includes an upper heating device 8 and a lower heating device 11. The upper heating device 8 is arranged on the tool string body between the primer spraying device 6 and the topcoat spraying device 9; The lower heating device 11 is arranged on the tool string body between the topcoat spraying device 9 and the surface treatment device 12; Both the upper heating device 8 and the lower heating device 11 are connected to the power supply through cables.

[0020] In one embodiment, the heating device is an electric heating sleeve.

[0021] In one embodiment, the topcoat spraying device 9 is a pneumatic airless spraying machine, specifically, it can be a GPQ9CA pneumatic airless spraying machine, produced by Tianjin Binhai New Area Tanggu Yihui Sandblasting and Spraying Equipment Co., Ltd. The pneumatic airless spraying machine sprays out by relying on the power provided by the compressed air in the air compressor of the supply system. The supply system is a device for supplying topcoat to the pneumatic airless spraying machine in the prior art.

[0022] In one embodiment, the primer spraying device 6 is a Reactor hydraulic two-component spraying machine, specifically, it can be a Reactor hydraulic two-component spraying equipment H-XP3, produced by Graco Inc., USA. The Reactor hydraulic two-component spraying machine sprays out by relying on the power provided by the compressed air compressed by the air compressor in the supply system. The supply system is a device for supplying primer to the hydraulic two-component spraying machine in the prior art.

[0023] In one embodiment, the surface treatment device 12 is a suction type dry sandblasting machine, specifically, it can be a GS-0722 type special suction type dry sandblasting machine for oil pipes, produced by Beijing Huizhi Tongchuang Technology Development Co., Ltd. The suction type dry sandblasting machine sprays out by relying on the power provided by the compressed air in the air compressor of the supply system. The supply system is a device for supplying abrasive to the suction type dry sandblasting machine in the prior art.

[0024] In one embodiment, the primer spray holes 7, the topcoat spray holes 10 and the abrasive spray holes 13 are respectively arranged in two; 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 two sides of the corresponding positions of the tool string body.

[0025] A construction method for the anti-corrosion coating of the downhole casing of an oil and gas well, using a construction device for the anti-corrosion coating of the downhole casing of an oil and gas well, includes the following steps: Step 1, use a scraper and a drift of appropriate size to process the entire wellbore of the target oil and gas well, eliminate the burrs on the inner wall of the wellbore casing 16, and keep the subsequent tools operating normally for tripping in and out. Step 2, wash the entire wellbore to remove dirt, sludge and other sundries on the inner wall of the wellbore casing 16. Step 3, connect the power supply and the supply system 1 to the tool string body through the cable and pipeline system 2, and lower it into the wellbore casing 16 of the oil and gas well through the pulley 3. Step 4, install the safety joint 4 on the top of the tool string body to ensure that when the tool string gets stuck abnormally, the tool string can be disconnected from the cable and pipeline system 2. Step 5, then install a centralizer 5 on the upper part of the tool string body, and its function is to keep the entire tool string body in the central position in the wellbore. Step 6: During the process of the tool string body descending from the wellhead to the bottom of the well, the surface treatment device 12 at the lower part of the tool string body sprays the foam system mixed with abrasives on the ground onto the inner wall of the casing through the abrasive spray holes 13 to polish and roughen the inner wall of the casing, thereby expanding the surface area of the inner wall of the casing. Step 7: During the descending process of the tool string, the upper heating device 8 and the lower heating device 11 are simultaneously turned on to dry the inner surface of the casing. Step 8: When the tool string reaches the designed bottom position, the surface treatment device 12 stops working, and the ground operation triggers the electric pin 14, causing the retrievable bridge plug 15 to be set at the designated position and separated from the electric pin 14. Step 9: The tool string body starts to ascend from the bottom position, and the primer spraying device 6 starts to work. The power supply and supply system 1 sprays the primer evenly onto the inner wall of the casing from the primer spray holes 7 through the pipelines in the cable and pipeline system 2. The upper heating device 8 promptly dries the primer. Step 10: During the ascending process of the tool string, the topcoat spraying system also starts. The ground supply system sprays the topcoat evenly onto the inner wall of the casing through the topcoat spray holes 10. The lower heating device 11 promptly dries the topcoat, enabling the anti-corrosion coating to quickly form a stable protective layer on the inner wall of the casing. Step 11: After the tool string is retrieved from the entire wellbore of the target oil and gas well, a fishing tool for the retrievable bridge plug 15 is lowered to fish out the bridge plug, keeping the production casing of the entire wellbore of the target oil and gas well unobstructed. Step 12: The oil and gas well conducts normal production operations to complete the construction of the anti-carbon dioxide corrosion coating for the downhole casing of the oil and gas well.

[0026] The present invention is a construction method for the anti-corrosion coating carried out during the service stage of the casing of an oil and gas well, where the casing has been cemented underground. Compared with the current method of adding chemicals regularly for anti-corrosion, this method has low labor intensity, strong operability, a fast formation speed of the anti-spray coating, strong tolerance, low cost, and good anti-corrosion effect.

Claims

1. A construction device for an anti-corrosion coating of an underground casing in an oil and gas well, comprising a tool string body, a safety joint is connected to one end of the tool string body, and a retrievable bridge plug is arranged at the other end of the tool string body, and the retrievable bridge plug is connected to the tool string body through an electric pin; characterized in that, 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 retrievable bridge plug; The primer spraying device, the topcoat spraying device, the surface treatment device and the heating device are all connected to a power source through cables; the primer spraying device, the topcoat spraying device and the surface treatment device are respectively connected to the power source and the supply system through cables and pipeline systems; Primer spray holes, topcoat spray holes and abrasive spray holes are respectively provided at positions corresponding to the primer spraying device, the topcoat spraying device and the surface treatment device on the tool string body, and the primer spraying device, the topcoat spraying device and the surface treatment device respectively spray spraying materials through the primer spray holes, the topcoat spray holes and the abrasive spray holes; A centralizer is also connected to one end of the tool string where the safety joint is provided.

2. The construction device for the anti-corrosion coating of the downhole casing of an oil and gas well according to claim 1, characterized in that, 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 through cables.

3. The construction device for the anti-corrosion coating of the downhole casing of an oil and gas well according to claim 1, characterized in that, The heating device is an electric heating sleeve.

4. The construction device for the anti-corrosion coating of the downhole casing of an oil and gas well according to claim 1, wherein, The topcoat spraying device is a pneumatic airless spraying machine.

5. The construction device for the anti-corrosion coating of the downhole casing of an oil and gas well according to claim 1, characterized in that, The primer spraying device is a Reactor hydraulic-two-component spraying machine.

6. The construction device for the anti-corrosion coating of the downhole casing of an oil and gas well according to claim 1, characterized in that, The surface treatment device is a suction type dry sandblasting machine.

7. The construction device for the anti-corrosion coating of the downhole casing of an oil and gas well according to claim 1, wherein, The primer spray holes, the topcoat spray holes and the abrasive spray holes are respectively provided as two; the two primer spray holes, the two topcoat spray holes and the two abrasive spray holes are symmetrically provided on the corresponding two sides of the corresponding positions of the tool string body.

8. A construction method for an anti-corrosion coating of an underground casing in an oil and gas well, using the construction device for an anti-corrosion coating of an underground casing in an oil and gas well as described in claim 2, including the following steps: Step 1, use a scraper and a drift of appropriate sizes to process the entire wellbore of the target oil and gas well, eliminate burrs on the inner wall of the wellbore casing, and ensure normal tripping operations of subsequent tools; Step 2, wash the entire wellbore to remove dirt, sludge and other debris on the inner wall of the wellbore casing; Step 3, connect the power source and the supply system to the tool string through cables and pipeline systems, and lower them into the casing of the oil and gas wellbore through a pulley; Step 4, install the safety joint on the top of the tool string body to ensure that when the tool string is abnormally stuck, the tool string can be disconnected from the cable and pipeline systems; Step 5, then install a centralizer on the upper part of the tool string body, and its function is to keep the entire tool string body in the central position in the wellbore; Step 6, when the tool string body descends from the wellhead to the bottom of the well, the surface treatment device at the lower part of the tool string body sprays the foam system mixed with abrasives on the ground onto the inner wall of the casing through the abrasive spray holes, grinds the inner wall of the casing, roughens it, and enlarges the surface area of the inner wall of the casing; Step 7, during the downward movement of the tool string, the upper heating device and the lower heating device are turned on simultaneously to dry the inner surface of the casing; Step 8, when the tool string reaches the designed bottom position, the surface treatment device stops working, and the ground operation triggers an electric pin, and the retrievable bridge plug is set to the designated position and disengages from the electric pin; Step 9, the tool string body starts to move upward from the bottom hole position, and the primer spraying device starts to work. The power supply and supply system evenly spray the primer from the primer spray holes on the inner wall of the casing through the pipelines in the cable and pipeline system, and the upper heating device promptly dries the primer; Step 10, during the upward movement of the tool string, the topcoat spraying system also starts. The ground supply system evenly sprays the topcoat on the inner wall of the casing through the topcoat spray holes, and the lower heating device promptly dries the topcoat, 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 is taken out of the entire wellbore of the target oil and gas well, a fishing tool for the retrievable bridge plug is lowered to fish out the bridge plug, so that the production casing of the entire wellbore of the target oil and gas well remains unobstructed; Step 12, the oil and gas well conducts normal production operations to complete the construction of the carbon dioxide corrosion prevention coating for the downhole casing of the oil and gas well.

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