An oil well casing reconstruction device and a reconstruction method

Abstract

The present invention discloses an oil well casing reconstruction device, which includes a first connecting pipe and a second connecting pipe. The first connecting pipe and the second connecting pipe are coaxially connected and fixed through a switch sliding sleeve. A sheet-shaped organic material is wrapped around the outer wall of the switch sliding sleeve. One end port of the first connecting pipe away from the switch sliding sleeve is connected with a variable-coupling collar. A ball seat is fixed on the inner wall of the second connecting pipe, and a setting ball is matched with the ball seat. The present invention also discloses a reconstruction method based on the above reconstruction device. It solves the problems existing in the prior art that the chemical plugging agent composite metal expansion pipe needs to be expanded multiple times, the sealing between the metal pipe and the organic plugging agent is difficult, and it is difficult to effectively seal and fit with the damaged pipe section with irregular and complex morphologies.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil extraction, and relates to a device for reconstructing an oil well casing. Further, it relates to a method for reconstructing the above device. Background Art

[0002] In oilfield production, the steel casings of oil wells, gas wells or injection wells often suffer from local corrosion on the inner or outer walls of the casings due to contact with oil, gas, water media containing CO2, H2S and / or corrosive bacteria, or contact with corrosive treatment fluids such as aggressive measures of acidification and plug removal of the well, etc., and then form volumetric damage penetrating the entire casing wall thickness, damaging the integrity of the wellbore casing. When the casing is damaged, the commonly used treatment and repair methods are: (1) Mechanical separate production, that is, using mechanical water shutoff and oil production tools to seal off the damaged section of the casing and resume production of the producing formation; (2) Chemical plugging, that is, using chemical methods and supporting chemical plugging agents to permanently plug the damaged part of the casing through chemical action; (3) Solid expandable tube patch, using a metal tube to deform under the extrusion of an expansion tool and patch the damaged part of the casing; (4) Running a smaller casing, for oil wells where large sections of casing damage cannot be seated, a new casing with an inner diameter smaller than that of the original wellbore casing is run during workover to resume production of the oil well; (5) Using the available upper casing and wellbore to carry out window sidetracking, drilling a new wellbore trajectory and running a casing, while abandoning the damaged section of the lower wellbore.

[0003] In the method of plugging channeling and leakage, currently mainly cement, resin, organic materials, etc. are used for chemical plugging. Mostly, mechanical bridge plugs are used to seal off the producing formation, the tool tubing is used to displace the plugging agent to near the leakage point, the pipe string is pulled out 100 - 200 meters, and then the casing is closed and the plugging agent is squeezed in, and the pressure is maintained and left to set. The process is cumbersome and the operation time is long. Chinese Patent No.: CN106351603B discloses a method for plugging severe leakage in fractures or karst caves and a pipe string for delivering plugging materials. The plugging materials are bridging aids such as rubber, hydration swelling materials and shear thickening fluids, and the plugging operation is carried out on the lost circulation section of the well through the pipe string for delivering plugging materials. The disadvantage is that the compressive capacity is insufficient and it is not suitable for plugging the lost circulation section of old wells. Chinese Patent No.: CN106014330A discloses a method for improving the success rate of chemical plugging in lost circulation and casing damaged wells. The plugging materials are phosphate cement or aluminate cement added with quartz, calcite or marble particles, and the method of pre - cleaning, intermediate plugging and interval displacement is used to plug large - section lost circulation. However, its pressure test can only reach 15 MPa and cannot meet the requirements of plugging operations for old wells.

[0004] In the past two years, research on high-strength organic resin materials has been intensively carried out at home and abroad. Compared with conventional cement, polymer resin is an excellent material for plugging oil wells because of its low-viscosity injection and good rheology, high resistance to salt, acid, and oil, strong compressive capacity, long effective period, and ability to enter micro-pore channels. Chinese Patent No.: CN110105932A discloses a resin material for plugging oil and gas well casings and its preparation method, which is applicable not only to plugging damaged production well casings but also to the needs of plugging damaged casings in new well fracturing and old well repeated transformation of old fractures. Corresponding foreign patents include US20120446415A1, US2011152394A1, etc.

[0005] In the subsidy plugging method, there are two systems of expansion subsidy pipes adopted in current domestic and foreign projects and literature: steel solid expansion pipes and expansion pipes composed of shape memory alloy and rubber composites. In the subsidy method of steel solid expansion pipes, the main method adopted by companies such as Evanchi in the United States is to lower the expansion pipe to the predetermined subsidy position in the well, and through a mechanical expansion device, rely on liquid pressure to push. During the movement of the expansion cone or mandrel, the expansion pipe expands, and through plastic deformation, the purpose of expanding the pipe diameter is achieved. Then, it is suspended together with the casing subsidy by using a sealing rubber ring or special sealing thread until the expansion subsidy is completed. The expansion process can be carried out by hydraulic expansion alone, single lifting expansion, or a combination of hydraulic and lifting expansion. Relatively typical foreign patents include US5040283A, US20050067170A1, US9194218B2, etc., and domestic patents include CN109707333B, CN105604516B, etc.

[0006] The disadvantages of this process are as follows: 1. When the damaged section of the casing is relatively long (generally with a length > 10m), before hydraulic expansion of the subsidy pipe, special threaded collars and rubber sealing rings must be used. After several subsidy pipes are connected through threaded collars, during the hydraulic expansion process, the long pipe section gradually expands to achieve a tight fit between the subsidy pipe and the inner wall of the well casing. However, the connection and sealing of threaded collars and the like are prone to failure, greatly increasing the construction difficulty and prolonging the operation cycle; 2. The main material of the subsidy pipe is carbon steel, and it is difficult to avoid secondary corrosion in the downhole environment. However, using materials such as nickel-based, chromium-based corrosion-resistant alloys or titanium alloys will lead to a significant increase in cost, and their material properties such as the hardness of the body and the hydraulic expansion elongation rate are completely different from those of carbon steel, which will further complicate the expansion process. 3. After casing subsidy, there will be a certain degree of reduction in the inner diameter. For example, After the subsidy of the inner diameter casing, the inner diameter is reduced to which leads to further complication of the subsequent production restoration and measure operations.

[0007] In recent years, there has also been a process in this field that uses an organic composite round tube for expansion and pasting, such as the method described in a foreign article translated by Liu Jinghao et al. (Unique Cable Conveying Casing Leakage Repair Technology, Petroleum Machinery, Vol. 31, No. 3, pp. 56 - 57, 2003). There has also been a process that uses a shape memory alloy tube or cylinder combined with rubber for expansion and patching, as seen in CN105604516A and CN108661585A. However, when dealing with long-section casing damaged wells (generally with a length > 10m), when the composite material round tube is lowered during wellhead operations, it needs to be pre-coiled onto a drum in advance, and it also needs to be longitudinally penetrated through the outside of operation strings such as tubing, coiled tubing, or cables. The operation procedures and processes are relatively complex. Summary of the Invention

[0008] The object of the present invention is to provide an oil well casing reconstruction device, which solves the problems existing in the prior art that the chemical plugging agent composite metal expansion tube requires multiple expansion processes, the sealing between the metal tube and the organic plugging agent is difficult, and it is difficult to effectively seal and fit with the damaged tube sections with irregular and complex morphologies.

[0009] Another object of the present invention is to provide a reconstruction method based on the above reconstruction device.

[0010] One technical solution adopted by the present invention is:

[0011] An oil well casing reconstruction device includes a first connecting pipe and a second connecting pipe. The first connecting pipe and the second connecting pipe are coaxially connected and fixed through a switch sliding sleeve. A sheet-shaped organic material is wrapped around the outer wall of the switch sliding sleeve. One end port of the first connecting pipe away from the switch sliding sleeve is connected with a variable-coupling collar. A ball seat is fixed on the inner wall of the second connecting pipe, and a setting ball is matched with the ball seat.

[0012] The characteristics of the present invention also lie in:

[0013] Threads are provided on the outer wall of one end port of the first connecting pipe away from the switch sliding sleeve, and one end of the variable-coupling collar is threadedly connected with the first connecting pipe.

[0014] The length of the sheet-shaped organic material is not less than the diameter of the first connecting pipe. The two ends of the sheet-shaped organic material are folded up to form connecting hooks with a concave-convex keyway structure. The sheet-shaped organic material is wound around the outer wall of the switch sliding sleeve and locked and fixed with a set of pins.

[0015] A thermal release agent is coated on the surface of the sheet-shaped organic material.

[0016] The set of pins is multiple pins, and the multiple pins are fixed on the sheet-shaped organic material at equal intervals in a row.

[0017] Another technical solution adopted by the present invention is:

[0018] A method for reconstructing an oil well casing, using the above-mentioned oil well casing reconstruction device to perform reconstruction operations on the oil well casing. The specific steps are as follows:

[0019] Step 1: Select an oil well with damaged casing and remove the original well string.

[0020] Step 2: Determine the damaged part of the casing and the size of the damaged section, and clean the damaged part of the casing by means of well flushing, pipe scraping or chemical cleaning.

[0021] Step 3: Isolate the lower medium and space of the oil well by setting a packer bridge plug or sand plug below the damaged part of the casing.

[0022] Step 4: Connect the other end of the reducer coupling to the work string, lower the oil well casing reconstruction device of the present invention into the oil well through the work string, and align the sheet-shaped organic material with the damaged part of the casing.

[0023] Step 5: Inject organic plugging resin into the work string, then put a setting ball into the work string and inject kill fluid to build up pressure, so that the setting ball continuously falls to open the switch sleeve and lands on the ball seat. During this process, the expansion pressure continuously increases, the switch sleeve opens, and the organic plugging resin goes out through the switch sleeve and expands the sheet-shaped organic material, so that the connecting hooks at both ends of the sheet-shaped organic material are buckled with each other, and the sheet-shaped organic material and the organic plugging resin are completely attached to the damaged part.

[0024] Step 6: Close the wellhead valve, wait for the organic plugging resin to cure, then remove the work string and the reconstruction device, and the work is completed.

[0025] In Step 2, after being lowered into the well, the upper edge of the sheet-shaped organic material is located 2-3 meters above the upper edge of the damaged part, and the lower edge of the sheet-shaped organic material is located 2-3 meters below the lower edge of the damaged part.

[0026] The thickness of the sheet-shaped organic material is 1-5 mm, and the internal pressure resistance after sealing is 5-10 MPa.

[0027] The material of the sheet-shaped organic material is an oil-soluble thermoplastic organic substance.

[0028] The density of the organic plugging resin is generally 1.2 g / cm 3 ~1.8 g / cm 3 , its component is two-component, and the ratio of the first component to the second component is 3-5:1. The first component is epoxy resin or modified epoxy resin or modified epoxy phenolic resin, and the second component is modified imidazole or modified polyamide or modified aliphatic amine. The viscosity injected into the well is 100 mPa·s~1000 mPa·s.

[0029] The beneficial effects of the present invention are:

[0030] 1. By attaching a thermoplastic organic material ring outside the target pipe string, and through the action of physical deformation force and resin cementing force, the damaged section of the casing is sealed by fitting, achieving the purpose of one-time operation to complete procedures such as injecting plugging agent, expansion subsidy, and releasing the string, reducing the cost of tripping in and out of the well and labor intensity, especially reducing the tripping in and out of the well risk in wells with a relatively high hydrogen sulfide content.

[0031] 2. The device of the present invention can select different specifications of the reconstruction device according to the inner diameter of the oil well casing, with strong process adaptability, which can effectively reduce the operation cost, operation time and labor intensity. The construction process is simple and easy to implement, with strong operability, which has a certain promoting effect on the popularization and application of this technology.

[0032] 3. The organic material ring of the present invention can be gradually dissolved with the production of the oil well, and finally ensure that the inner diameter of the oil well casing after the reconstruction operation remains unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a structural diagram of a device for reconstructing an oil well casing of the present invention;

[0034] Figure 2 is Figure 1 a sectional view of part A - A in

[0035] Figure 3 is a schematic diagram after the step 4 of a method for reconstructing an oil well casing of the present invention is lowered into the well;

[0036] Figure 4 is a schematic diagram of injecting organic plugging resin in the step 5 of a method for reconstructing an oil well casing of the present invention;

[0037] Figure 5 is a schematic diagram after the setting ball is put in the step 5 of a method for reconstructing an oil well casing of the present invention;

[0038] Figure 6 is a schematic diagram after the organic plugging resin is cured in the step 6 of a method for reconstructing an oil well casing of the present invention.

[0039] In the figures, 1. operation pipe string, 2. variable coupling, 3. sheet-shaped organic material, 4. switch sliding sleeve, 5. setting ball, 6. ball seat, 7. connecting hook, 8. thermal release agent, 9. pin group, 10. first connecting pipe, 11. second connecting pipe, 12. kill fluid, 13. organic plugging resin, 14. damaged part, 15. bridge plug. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0041] A device for reconstructing an oil well casing of the present invention, as shown in Figure 1 and Figure 2, including a first connecting pipe 10 and a second connecting pipe 11. The first connecting pipe 10 and the second connecting pipe 11 are coaxially connected and fixed through a switch sliding sleeve 4. A sheet-shaped organic material 3 is wrapped around the outer wall of the switch sliding sleeve 4. One end port of the first connecting pipe 10 away from the switch sliding sleeve 4 is connected with a variable coupling collar 2. A ball seat 6 is fixed on the inner wall of the second connecting pipe 11, and a seat sealing ball 5 is provided for the ball seat 6.

[0042] Threads are provided on the outer wall of one end port of the first connecting pipe 10 away from the switch sliding sleeve 4, and one end of the variable coupling collar 2 is threadedly connected with the first connecting pipe 10.

[0043] The length of the sheet-shaped organic material 3 is not less than the diameter of the first connecting pipe 10. Both ends of the sheet-shaped organic material 3 are folded up to form connecting hooks 7 with a concave-convex keyway structure. The sheet-shaped organic material 3 is wound around the outer wall of the switch sliding sleeve 4 and locked and fixed with a pin group 9. A thermal release agent 8 is coated on the surface of the sheet-shaped organic material 3.

[0044] The pin group 9 is composed of multiple pins, and the multiple pins are fixed in rows on the sheet-shaped organic material 3 at equal intervals.

[0045] A method for reconstructing an oil well casing uses the above-mentioned oil well casing reconstruction device to perform reconstruction operations on the oil well casing. The specific steps are as follows:

[0046] Step 1: Select an oil well with damaged casing and lift out the original well string.

[0047] Step 2: Determine the damaged part 14 of the casing and the size of the damaged section, and clean the damaged part 14 of the casing by means of well flushing, scraping or chemical cleaning.

[0048] Step 3: Isolate the lower medium and space of the oil well by means of a seat sealing bridge plug 15 or sand plugging below the damaged part 14.

[0049] Step 4: Connect the other end of the variable coupling collar 2 with the work string 1, and lower the oil well casing reconstruction device of the present invention into the oil well through the work string 1. For example, Figure 3 , align the sheet-shaped organic material 3 with the damaged part 14 of the casing.

[0050] Step 5: For example, Figure 4 and Figure 5 , after squeezing organic plugging resin 13 into the work string 1, put the seat sealing ball 5 into the work string 1 and then inject well killing fluid 12 into it to build up pressure, so that the seat sealing ball 5 continuously falls to open the switch sliding sleeve 4 and lands on the ball seat 6. During this process, the expansion pressure continuously increases, the switch sliding sleeve 4 opens, and the organic plugging resin 13 goes out from the switch sliding sleeve 4 and expands the sheet-shaped organic material 3, so that the connecting hooks 7 at both ends of the sheet-shaped organic material 3 are buckled with each other, and the sheet-shaped organic material 3 and the organic plugging resin 13 are completely attached to the damaged part 14.

[0051] Step 6, as Figure 6 , close the wellhead valve. After waiting for the organic plugging resin 13 to cure, lift out the work string 1 and the reconstruction device, and the work is completed.

[0052] In Step 2, after going down the well, the upper edge of the sheet organic material 3 is located 2 - 3 meters above the upper edge of the damaged part 14, and the lower edge of the sheet organic material 3 is located 2 - 3 meters below the lower edge of the damaged part 14.

[0053] The thickness of the sheet organic material 3 is 1 - 5 mm, and the internal pressure resistance strength after sealing is 5 - 10 MPa.

[0054] The material of the sheet organic material 3 is an oil-soluble thermoplastic organic substance.

[0055] The density of the organic plugging resin 13 is 1.2 g / cm3 - 1.8 g / cm3. Its component is two-component, and the ratio of the first component to the second component is 3 - 5:1. The first component is epoxy resin or modified epoxy resin or modified epoxy phenolic resin, and the second component is modified imidazole or modified polyamide or modified aliphatic amine. The viscosity when injected into the well is 100 mPa·s - 1000 mPa·s.

[0056] Example 1:

[0057] Well * was put into production in October 2010; in March 2017, the water cut suddenly rose to 100%, and the flowing fluid level was 259 m. It was analyzed that the casing was corroded and perforated. The operation process is as follows:

[0058] Step 1, lift out the original well string.

[0059] Step 2, ream the well: lower a reamer with a diameter of Φ118 mm × 1.5 m to the artificial bottom hole.

[0060] Find the leak: Use a packer to test for leaks and water absorption in the whole well section, and the water absorption at the leak point should be no less than 5 m 3 (After pressurizing until the pressure is stable, determine the water absorption at the leak point), and the position of the perforation point is determined to be at 1608 m, and the water absorption > 300 L / min.

[0061] Step 3, set the bridge plug 15 at the position of 1710 m, and lower the reconstruction device to 1605 m.

[0062] Step 4, connect the work string 1 and the reconstruction device through the device reducer coupling 2 and lower them into the wellbore to align with the damaged part 14. The upper edge of the sheet organic material 3 is located 2 meters above the upper edge of the damaged part 14, and the lower edge of the sheet organic material 3 is located 3 meters below the lower edge of the damaged part 14. The thickness of the sheet organic material 3 is 5 mm, and the internal pressure resistance strength after sealing is 5 - 10 MPa.

[0063] Step 5, prepare the organic plugging resin 13, with a density of 1.2 g / cm3 It is formulated by epoxy resin and modified polyamide in a ratio of 3:1, and the viscosity injected into the well is 800 mPa·s.

[0064] Open the casing valve and pump 2 - 2.5 m of the organic plugging agent. 3 After using clear water as the kill fluid to displace 12 m to the leaking interval, close the casing valve, and squeeze clear water from the tubing to make the plugging agent enter the formation, with the pressure controlled at 18 - 20 MPa.

[0065] Insert the setting ball 5 from the upper inlet of the work string 1, apply pressure to open the switch sliding sleeve 4, increase the expansion pressure, open the sheet organic material 3, and make the connecting hooks 7 at both ends of the sheet organic material 3 engage with each other, and the sheet organic material 3 is completely attached to the organic plugging resin 13;

[0066] Step 6: Close the wellhead valve and wait for 48 h for setting; wait for the organic plugging resin 13 to cure. A large amount of heat is released during the curing process. After the temperature exceeds 50 °C, the organic material ring further thermally expands, and through the action of physical deformation force and resin bonding force, it fits and seals the damaged part 14 of the casing;

[0067] Pull out the drill pipe and conduct a pressure test. Lift it to 35 kN, and the pulling force quickly drops to 27 kN, indicating that the pipe string is completely separated from the plugging agent material. Conduct a pressure test on the wellbore at 15 MPa, and the pressure drop within 30 min ≤ 0.5 MPa.

[0068] Drill out the plug: Lower the drill-out pipe string, strictly execute the drill-out and well flushing specifications, and flush the well until the water quality at the inlet and outlet is the same for each drill pipe. Complete the well with a pump.

[0069] After the implementation of this embodiment, the well resumes production capacity, with a daily oil production of 2.65 t and a water cut of 29.6%.

[0070] Example 2:

[0071] After 8 years of production of Well * in Zhen*, the water cut rises to 100%, the flowing fluid level is 562 m, and the workover logging analysis shows that there is a leak at the coupling.

[0072] Step 1: Pull out the original well pipe string.

[0073] Step 2: Ream the well. Lower a reamer gauge with a diameter of Φ118 mm × 1.5 m to the artificial bottom hole.

[0074] Find the leak: Use a packer to test the leak and find the water absorption throughout the well section. The water absorption at the leak point should be no less than 5 m 3 (After the pressure stabilizes after applying pressure, determine the water absorption at the leak point), and the leak point is determined to be at 1385.0 m, with a water absorption < 100 L / min.

[0075] Step 3: Set the bridge plug 15 at a position of 1435.0 m, and lower the reconstruction device to 1382.0 m.

[0076] Step 4: The work string 1 and the reconstruction device are connected by a device reducer collar 2 and lowered into the wellbore to align with the damaged part 14. The upper edge of the sheet organic material 3 is located 3 meters above the upper edge of the damaged part 14, and the lower edge of the sheet organic material 3 is located 2 meters below the lower edge of the damaged part 14. The thickness of the sheet organic material 3 is 4 mm, and the internal pressure resistance strength after sealing is 5 - 10 MPa.

[0077] Step 5: Prepare the organic plugging resin 13 with a density of 1.8 g / cm 3 , which is prepared by mixing modified epoxy phenolic resin and modified imidazole in a ratio of 5:1, and the viscosity injected into the well is 100 mPa·s.

[0078] Open the casing valve and pump 1 - 1.5 m of the organic plugging agent 3 . After displacing with clean water to the leaking interval, close the casing valve, and squeeze clean water from the tubing to make the plugging agent enter the formation, with the pressure controlled at 18 - 20 MPa.

[0079] Drop the setting ball 5 from the upper end inlet of the work string 1, apply pressure to open the switch sleeve 4, increase the expansion pressure, open the sheet organic material 3, and make the connecting hooks 7 at both ends of the sheet organic material 3 engage with each other, and the sheet organic material 3 is completely attached to the organic plugging resin 13;

[0080] Step 6: Close the wellhead valve and wait for coagulation for 48 h to wait for the organic plugging resin 13 to cure. A large amount of heat is released during the resin curing process. When the temperature exceeds 50 °C, the organic material ring further thermally expands, and through the action of physical deformation force and resin adhesion force, it fits and seals the damaged part 14 of the casing;

[0081] Pull out the drill string and conduct a pressure test. Lift it to 35 kN, and the pulling force quickly drops to 27 kN, indicating that the drill string is completely separated from the plugging agent material. Conduct a 15 MPa pressure test on the wellbore, and the pressure drop within 30 min ≤ 0.5 MPa.

[0082] Drill the plug: Lower the drill string for plug drilling, strictly implement the drill plug washing well specification, wash the well until the water quality at the inlet and outlet is the same for each drill pipe, and complete the well with a pump.

[0083] Example 3:

[0084] After the well has been in production for 7 years, the water cut has risen to 100%, the flowing fluid level is 438 m, and the well logging analysis shows serious corrosion perforation.

[0085] Step 1: Pull out the original well string.

[0086] Step 2: Ream the well: Lower a reamer with a diameter of Φ118 mm × 1.5 m to the artificial bottom hole.

[0087] Find the leak: Use a packer to test the leak and find the water absorption rate throughout the well section. The water absorption rate at the leak point should be no less than 5 m 3After being pressured down to a stable pressure, determine the water absorption volume at the leakage point, and determine that the leakage section is 29.2 m in total from 1462.8 m to 1492.0 m. Water absorption situation: continuously inject stably at a pressure of 14 MPa, with a displacement of 120 L / min and a water absorption volume of 2 m 3 。

[0088] Step 3: The setting position of 15 bridge plugs is at 1514.0 m, and the reconstruction device is lowered to 1495.0 m. The length of the sheet-shaped organic material 3 is 34 meters.

[0089] Step 4: The operation string 1 and the reconstruction device are connected and lowered into the wellbore through the device reducer coupling 2 and aligned with the damaged part 14. The upper edge of the sheet-shaped organic material 3 is 3 meters above the upper edge of the damaged part 14, the lower edge of the sheet-shaped organic material 3 is 3 meters below the lower edge of the damaged part 14, the thickness of the sheet-shaped organic material 3 is 1 mm, and the internal pressure resistance strength after sealing is 5 - 10 MPa.

[0090] Step 5: Prepare the organic plugging resin 13 with a density of 1.5 g / cm 3 It is prepared by mixing the modified epoxy resin and the modified fatty amine in a ratio of 5:1, and the viscosity injected into the well is 500 mPa·s.

[0091] Open the casing valve and pump 1.5 m of the organic plugging agent 3 。After displacing with clean water to the leakage layer section, close the casing valve, and squeeze clean water from the tubing to make the plugging agent enter the formation, with the pressure controlled at 18 - 20 MPa.

[0092] Put the setting ball 5 into the upper end inlet of the operation string 1, apply pressure to open the switch sliding sleeve 4, increase the expansion pressure, open the sheet-shaped organic material 3, and make the connecting hooks 7 at both ends of the sheet-shaped organic material 3 engage with each other, and the sheet-shaped organic material 3 is completely attached to the organic plugging resin 13;

[0093] Step 6: Close the wellhead valve and wait for 48 h for the organic plugging resin 13 to cure. A large amount of heat is released during the resin curing process. When the temperature exceeds 50 °C, the organic material ring further expands thermally, and through the action of physical deformation force and resin adhesion force, it fits and seals the damaged part 14 of the casing;

[0094] Pull out the drill string and conduct a pressure test. Lift it to 35 kN, and the pulling force quickly drops to 27 kN, indicating that the drill string is completely peeled off from the plugging agent material. Conduct a pressure test on the wellbore at 15 MPa, and the pressure drop within 30 min ≤ 0.5 MPa.

[0095] Drill the plug: Lower the drill string for plug removal, strictly implement the drill string washing specification for plug removal, wash the well until the water quality at the inlet and outlet is the same for each drill pipe, and then complete the well with a pump.

[0096] Example 4:

[0097] After the production of Well H started, the water cut was 100%, the flowing fluid level was 100 m, and the engineering logging analysis showed that a coupling at a certain location in the lower part of the wellbore was leaking.

[0098] Step 1: Pull out the original well string.

[0099] Step 2: Run a hole opener: Run a Φ118 mm × 1.5 m hole opener to the artificial bottom hole.

[0100] Leak detection: Use a packer to conduct sectional leak detection and water absorption testing for the whole well to find the water absorption volume of the leak point, and the water absorption volume of the leak point should be no less than 5 m 3 (After the pressure stabilizes after pressure application, determine the water absorption volume of the leak point), and the leaky section is determined to be 1317.0 m. Water absorption situation: Inject continuously and stably at a pressure of 12 MPa, with a displacement of 300 L / min and a water absorption volume of 1 m 3 .

[0101] Step 3: Set 15 bridge plugs at the position of 1450 m, and lower the reconstruction device to 1395.0 m.

[0102] Step 4: Connect the work string 1 and the reconstruction device through the device reducer coupling 2 and lower them into the wellbore to align with the damaged part 14. The upper edge of the sheet organic material 3 is 2 m above the upper edge of the damaged part 14, the lower edge of the sheet organic material 3 is 2 m below the lower edge of the damaged part 14, and the thickness of the sheet organic material 3 is 4 mm.

[0103] Step 5: Prepare the organic plugging resin 13 with a density of 1.2 g / cm 3 , which is prepared by mixing modified epoxy phenolic resin and modified aliphatic amine in a ratio of 4:1, and the viscosity injected into the well is 300 mPa·s.

[0104] Open the casing valve and pump 1.5 m of the organic plugging agent 3 . After displacing with clean water to the leaky layer section, close the casing valve, and squeeze clean water from the tubing to make the plugging agent enter the formation, with the pressure controlled at 18 - 20 MPa.

[0105] Drop the setting ball 5 from the upper end inlet of the work string 1, apply pressure to open the switch sleeve 4, increase the expansion pressure, open the sheet organic material 3, and make the connecting hooks 7 at both ends of the sheet organic material 3 engage with each other, so that the sheet organic material 3 is completely adhered to the organic plugging resin 13;

[0106] Step 6: Close the wellhead valve and wait for 48 h for the organic plugging resin 13 to cure. A large amount of heat is released during the resin curing process. When the temperature exceeds 50 °C, the organic material ring further thermally expands, and through the action of physical deformation force and resin adhesion force, it fits and seals the damaged part 14 of the casing;

[0107] Pull out the drill pipe and conduct pressure test. Lift it to 35 kN, and the pulling force quickly drops to 27 kN, indicating that the pipe string is completely separated from the plugging agent material. Conduct a pressure test on the wellbore at 15 MPa, and the pressure drop within 30 minutes ≤ 0.5 MPa.

[0108] Drill out the plug: Lower the drill string for plug removal, strictly implement the specification for washing the well during plug removal, wash the well until the water quality at the inlet and outlet is the same for each section of tubing drilled, and complete the well with a pump.

Claims

1. An oil well casing reconstruction device, characterized in that, It includes a first connecting pipe (10) and a second connecting pipe (11). The first connecting pipe (10) and the second connecting pipe (11) are coaxially connected and fixed through a switch sliding sleeve (4). A sheet-shaped organic material (3) is wrapped around the outer wall of the switch sliding sleeve (4). One end port of the first connecting pipe (10) far from the switch sliding sleeve (4) is connected with a variable-coupling collar (2). A ball seat (6) is fixed on the inner wall of the second connecting pipe (11), and a seat-sealing ball (5) is matched with the ball seat (6); The length of the sheet-shaped organic material (3) is not less than the diameter of the first connecting pipe (10). Both ends of the sheet-shaped organic material (3) are folded up to form connecting hooks (7) with a concave-convex keyway structure. The sheet-shaped organic material (3) is wound on the outer wall of the switch sliding sleeve (4) and locked and fixed with a pin group (9).

2. The oil well casing reconstruction device according to claim 1, characterized in that, Threads are provided on the outer wall of one end port of the first connecting pipe (10) far from the switch sliding sleeve (4). One end of the variable-coupling collar (2) is threadedly connected with the first connecting pipe (10).

3. The oil well casing reconstruction device according to claim 1, characterized in that, A thermal release agent (8) is coated on the surface of the sheet-shaped organic material (3).

4. The oil well casing reconstruction device according to claim 1, characterized in that, The pin group (9) is composed of multiple pins, and the multiple pins are fixed on the sheet-shaped organic material (3) in rows at equal intervals.

5. A method for reconstructing an oil well casing, characterized in that, Using a kind of oil well casing reconstruction device described in claim 1 to carry out reconstruction operation on the oil well casing, the specific steps are as follows: Step 1: Select an oil well with damaged casing and pull out the original well string; Step 2: Determine the damaged part (14) of the casing and the size of the damaged section, and clean the damaged part (14) of the casing by means of well flushing, pipe scraping or chemical cleaning; Step 3: Isolate the medium and space in the lower part of the oil well by means of a seat-sealing bridge plug (15) or sand plugging in the lower part of the damaged part (14); Step 4: Connect the other end of the variable-coupling collar (2) with the work string (1), lower a kind of oil well casing reconstruction device into the oil well through the work string (1), and align the sheet-shaped organic material (3) with the damaged part (14) of the casing; Step 5: After squeezing the organic plugging resin (13) into the work string (1), put the seat-sealing ball (5) into the work string (1), and then inject well control fluid (12) into it to build pressure, so that the seat-sealing ball (5) continuously falls to open the switch sliding sleeve (4) and falls onto the ball seat (6). During this process, the expansion pressure continuously rises, the switch sliding sleeve (4) opens, and the organic plugging resin (13) goes out from the switch sliding sleeve (4) and expands the sheet-shaped organic material (3), so that the connecting hooks (7) at both ends of the sheet-shaped organic material (3) are buckled with each other, and the sheet-shaped organic material (3) and the organic plugging resin (13) are completely attached to the damaged part (14); Step 6: Close the wellhead valve, wait for the organic plugging resin (13) to cure, and then pull out the work string (1) and the reconstruction device, and the work is completed.

6. The method for reconstructing an oil well casing according to claim 5, wherein, In the said Step 2, after going down the well, the upper edge of the sheet-shaped organic material (3) is located 2-3 meters above the upper edge of the damaged part (14), and the lower edge of the sheet-shaped organic material (3) is located 2-3 meters below the lower edge of the damaged part (14).

7. The method for reconstructing an oil well casing according to claim 5, characterized in that, The thickness of the sheet-shaped organic material (3) is 1-5 mm, and the internal pressure resistance strength after sealing is 5-10 MPa.

8. The method for reconstructing an oil well casing according to claim 5, wherein The sheet-like organic material (3) is made of an oil-soluble thermoplastic organic substance.

9. A method for reconstructing an oil well casing according to claim 5, characterized in that, The density of the organic plugging resin (13) is generally 1.2 g / cm 3 ~1.8 g / cm 3 , and it is composed of two components. The ratio of the first component to the second component is 3 - 5:

1. The first component is epoxy resin or modified epoxy resin or modified epoxy phenolic resin, and the second component is modified imidazole or modified polyamide or modified aliphatic amine. The viscosity when injected into the well is 100 mPa•s - 1000 mPa•s.

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