Oilfield casing leak detection tools and methods

Abstract

This invention relates to the field of oil well leak detection technology, specifically an oilfield casing leak detection tool and method. The tool comprises, from top to bottom, an external slip connector, a release mechanism, a centralizer, a bypass sub, a packer, a coupling locator, and a guide head, all fixedly installed together. The lower outer side of the bypass sub has several interconnecting holes evenly distributed around its circumference, each hole sealed with a threaded plug. This invention features a reasonable and compact structure, ease of use, and combines advantages such as long casing life, small tool size, short track-changing stroke, fast setting speed, prevention of coupling locator jamming and failure, and simultaneous leak detection above and below the packer. It improves leak detection efficiency, reduces construction complexity, shortens the construction cycle, meets low-cost and environmental protection requirements, and achieves high-efficiency treatment of damaged oilfield casing wells. It is safe, labor-saving, simple, and highly efficient.

Description

Technical Field

[0001] This invention relates to the field of oil well leak detection technology, and is a tool and method for leak detection in oilfield casing. Background Technology

[0002] With the vigorous development of my country's petroleum industry, casing damage has become a thorny problem restricting the development of oilfields. During oil and gas production, with the increase in the number of injection cycles, the number of wells with damaged casings gradually increases due to casing quality or formation pressure issues. Casing leaks are quite common, and casing damage frequently occurs in oil and gas wells. Casing leakage accounts for more than 50% of casing damage. Casing leakage can be categorized in many ways. On the one hand, casing leakage caused by poor sealing of the casing threads, small sandstone inclusions in the casing body, or micro-fractures is difficult to detect due to its small volume and high difficulty in routine operational inspections. It is only easily exposed during production processes such as fracturing and gas production, thus posing serious safety hazards and greatly affecting the effective development of oil and gas wells. On the other hand, some wells have leaks in the upper part of the oil layer, and there is a trend towards multiple leak points. Since water is leaking from all the leak points to varying degrees, steam will leak out during steam injection, causing the pumping unit to work futilely during production, increasing oil production costs. Furthermore, the backflow of water from the leak points will compress the oil layer, restricting the oil layer's production capacity and preventing the oil well from producing normally.

[0003] To promptly assess wellbore safety, it is urgent to utilize effective testing methods to identify the causes and locations of leaks, thereby enabling the rational selection of subsequent remediation solutions and accumulating relevant preventative technical experience for drilling, cementing, completion, and production projects. Traditional leak-finding techniques involve assembling a leak-finding string from top to bottom using a Y111 packer, short screen, Y211 packer, and dead plug. However, in practice, it has been found that the presence of condensed heavy oil in the wellbore frequently leads to packer setting failure. Furthermore, traditional leak-finding tools can only perform pressure testing on the upper part of the packer, requiring multiple setting and unsetting operations during the entire process, which can easily damage the packer. Summary of the Invention

[0004] This invention provides a casing leak detection tool and method for oilfields, which overcomes the shortcomings of the prior art and can effectively solve the problems of long cycle, multiple pressure testing and setting, and high operating costs of existing leak detection tools.

[0005] One of the technical solutions of the present invention is achieved through the following measures: an oilfield casing leak detection tool, comprising an external slip connector, a release handle, a centralizer, a bypass sub, a packer, a coupling locator, and a guide head, which are fixedly installed together from top to bottom. The lower outer side of the bypass sub has a number of interconnecting holes that are evenly distributed around the circumference, and each interconnecting hole is sealed with a threaded plug.

[0006] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: The packer described above may include a central tube, a track rod, a rubber sleeve, a friction block, a spring, a slip, and a pin. An upper connector is fixedly installed between the upper end of the central tube and the lower end of the bypass section. The lower end of the central tube is fixedly installed together with the upper end of the hollow track rod. An outer ring platform is fixed to the outer side of the lower part of the central tube. Several internally and externally communicating liquid outlet holes are evenly distributed along the circumference of the outer ring platform. A cone is fitted onto the outer side of the outer ring platform. The lower outer side of the cone has a tapered surface that is wider at the top and narrower at the bottom. An adjusting ring is fixedly installed on the outer side of the upper end of the cone. The upper part of the adjusting ring sits on the upper surface of the outer ring platform. The lower outer side of the cone, corresponding to the position below the adjusting ring, is fixedly installed on the outer side of the upper end of the cone. Several radially penetrating outflow liquid holes are evenly distributed along the circumference of the side. A rubber sleeve is fitted on the outer side of the upper part of the central tube corresponding to the upper end of the adjusting ring. A cone cap is fixed on the outer side of the upper part of the central tube corresponding to the upper end of the rubber sleeve. A lower connector is fixedly installed between the lower end of the track rod and the upper end of the coupling positioner. Several pairs of upward-opening V-shaped sliding grooves are evenly distributed along the circumference of the lower outer side of the track rod above the lower connector. A downward-opening V-shaped upper sliding groove is provided on the outer side of the track rod between every two adjacent sliding grooves. The upper part of each sliding groove is connected to the lower part of the corresponding upper sliding groove. Two outward-opening long slots are symmetrically arranged on the outer side of the middle section. The lower part of the two long slots is connected to the upper part of two symmetrically arranged upper sliding slots. A sliding cylinder is coaxially fitted on the outer side of the middle section of the track rod. Several mounting holes with internal and external connections are evenly distributed along the circumference of the upper outer side of the sliding cylinder. A slip is provided on the upper part of the sliding cylinder corresponding to each mounting hole. The inner side of the upper part of the slip is inclined to match the outer side of the lower end of the cone. An L-shaped connecting block is fixed at the lower end of each slip and installed in the corresponding mounting hole. Two pins are evenly distributed along the circumference of the lower part of the sliding cylinder. The ends of the two pins pass through the inner wall of the sliding cylinder. Located at the lower part of the two sliding grooves, a number of outward-facing mounting grooves are evenly distributed along the circumference of the outer side of the middle part of the sliding cylinder between the position below the mounting hole and above the pin. A locking block is fixed to the upper part of the sliding cylinder corresponding to each mounting groove position, and a mounting sleeve is fixedly installed on the lower outer side of the sliding cylinder. A friction block is installed in each mounting groove. An upper support block and a lower support block are fixed to the upper and lower ends of the friction block, respectively. An outward-facing arc-shaped spring is installed between each friction block and the inner wall of the mounting groove. The spring makes the outer side of the upper support block and the inner side of the locking block, as well as the outer side of the lower support block and the inner side of the upper end of the mounting sleeve, abut against each other.

[0007] Both the right side of the upper slide groove and the right side of the lower slide groove can be vertical. The inner side of the lower part of each lower slide groove and the upper part of each two adjacent lower slide grooves are smoothly transitioned. The lower part of each two adjacent upper slide grooves is also smoothly transitioned.

[0008] Each of the above-mentioned sliding grooves may have a first row of sand holes that penetrate radially at the bottom, and each long groove extends to the inner side of the track rod at the top. Each upper sliding groove corresponding to the position between two long grooves may have a second row of sand holes that penetrate radially at the top.

[0009] Each of the above mounting slots may have a radially penetrating third row of sand holes at the top and bottom, and a number of internally and externally connected strip-shaped fourth row of sand holes are distributed at intervals along the circumference on the outer side of the upper part of the track rod above the sliding groove.

[0010] An inner annular groove may be provided on the inner side of the middle part of the aforementioned rubber tube.

[0011] The aforementioned coupling positioner can be a spring-loaded coupling positioner.

[0012] The second technical solution of the present invention is achieved through the following measures: a method for finding leaks in a casing, comprising the following steps: The first step is to connect the lower end of the coiled tubing to the upper end of the external slip connector and lower it into the middle of the well, then record the initial position of the packer. The second step is to set the packer in the sleeve. The third step is to pump fluid into the annulus above the packer and the annulus below the packer, so that both the annulus above the packer and the annulus below the packer are pressurized. Fourth step: When the liquid pressure in both the annulus above and below the packer reaches the set value, stop the pump. Fifth, observe the rate of pressure drop in the casing annulus above and below the packer. Compare these rates with the standard pressure drop rate per unit time of the casing. When both rates are greater than the standard pressure drop rate per unit time, the pressure drop rate above the packer is considered normal. Both the casing below the packer and the casing below the packer have leaks. When the standard pressure drop rate per unit time of the casing is the same as the pressure drop rate of the fluid in the annulus of the casing below the packer and is less than the pressure drop rate of the fluid in the annulus of the casing above the packer, then only the casing above the packer has a leak. When the pressure drop rate of the fluid in the annulus of the casing above the packer is the same as the standard pressure drop rate per unit time of the casing and is less than the pressure drop rate of the fluid in the annulus of the casing below the packer, and the rates increase sequentially, then only the casing below the packer has a leak. Step 6: Determine the location of the leak.

[0013] The following are further optimizations and / or improvements to the second technical solution of the above invention: The sixth step above includes: (i) When the leak is only present in the casing above the packer, after unsealing the packer, raise the coiled tubing to a certain distance, and then repeat steps two through five. 1. If the leak is located in the sleeve below the packer, record the first position of the packer at this time to determine that the leak is located in the sleeve between the initial position and the first position of the packer; 2. If the leak is located on the casing above the packer, continue to unseal the packer and raise the coiled tubing to a certain distance and repeat steps 2 to 5 until the leak is determined to be located on the casing below the packer. Record the position of the packer at this time and the position of the packer when it was set last time. Determine that the leak is located on the casing between the current position of the packer and the position of the packer when it was set last time. 3 If the leaks are located on the sleeve above and below the packer, first record the second position of the packer at this time to determine that some leaks are located on the sleeve between the initial and second positions of the packer. Then, follow step 2 to determine the location of the remaining leaks. (ii) When the leak is only present in the casing below the packer, after unsealing the packer, lower the coiled tubing to a certain distance, and then repeat steps two through five. 1. If the leak is located on the sleeve above the packer, record the third position of the packer at this time to determine that the leak is located on the sleeve between the initial position and the third position of the packer; 2. If the leak is located in the casing below the packer, continue to unseal the packer and lower the coiled tubing to a certain distance and repeat steps 2 to 5 until the leak is determined to be located in the casing above the packer. Record the position of the packer at this time and the position of the packer during the previous setting. Determine that the leak is located in the casing between the current position of the packer and the position of the packer during the previous setting. 3 If the leaks are located on the sleeve above and below the packer, first record the fourth position of the packer at this time to determine that some leaks are located on the sleeve between the initial position and the fourth position of the packer. Then, follow step 2 to determine the location of the remaining leaks. (iii) When there are leaks in both the sleeve above the packer and the sleeve below the packer, determine the location of the leaks according to steps one and two respectively.

[0014] After the location of the leak is determined, the sleeve with the leak is accurately located using the coupling locator.

[0015] This invention has a reasonable and compact structure and is easy to use. It is a tool that combines the characteristics of long rubber sleeve life, small tool size, short rail changing stroke, fast setting speed, and the ability to simultaneously find leaks above and below the packer. It can improve leak finding efficiency, reduce construction complexity, shorten construction cycle, meet low cost and environmental protection requirements, and achieve high-efficiency treatment of oilfield casing damage wells. It is safe, labor-saving, simple and efficient. Attached Figure Description

[0016] Appendix Figure 1 This is a schematic diagram of the main structure of Embodiment 1.

[0017] Appendix Figure 2 This is a schematic diagram of the packer structure in Example 1.

[0018] Appendix Figure 3 This is a schematic diagram of the left cross-sectional structure of the packer in Example 1.

[0019] Appendix Figure 4 This is a schematic diagram of the track rod structure in Example 1.

[0020] The codes in the attached diagram are as follows: 1 is the external locking connector, 2 is the release handle, 3 is the centralizer, 4 is the coupling positioner, 5 is the bypass short section, 6 is the plug, 7 is the guide head, 8 is the upper support block, 9 is the lower support block, 10 is the center tube, 11 is the track rod, 12 is the rubber sleeve, 13 is the friction block, 14 is the spring, 15 is the locking piece, 16 is the pin, 17 is the upper connector, 18 is the lower connector, 19 is the cone cap, 20 is the adjusting ring, 21 is the cone, 22 is the inner liquid outlet, 23 is the slide cylinder, 24 is the connecting block, 25 is the mounting sleeve, 26 is the outer ring platform, 27 is the upper sliding groove, 28 is the lower sliding groove, 29 is the long groove, 30 is the first row of sand holes, 31 is the second row of sand holes, 32 is the third row of sand holes, 33 is the fourth row of sand holes, 34 is the inner ring groove, 35 is the mounting groove, 36 is the locking block, and 37 is the outer liquid outlet. Detailed Implementation

[0021] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0022] In this invention, for ease of description, the description of the relative positions of the components is based on the appendix to the specification. Figure 1 The layout is described using a diagrammatic method, such as front, back, top, bottom, left, right, etc. The positional relationships are determined based on the layout direction of the attached diagram in the instruction manual.

[0023] The present invention will be further described below with reference to embodiments and accompanying drawings: Example 1: As shown in the attached document Figure 1 , 2 As shown in Figures 3 and 4, the oilfield casing leak detection tool includes an external slip connector 1, a release handle 2, a centralizer 3, a bypass short section 5, a packer, a coupling locator 4, and a guide head 7, which are fixedly installed together from top to bottom. The lower outer side of the bypass short section 5 has several connecting holes that are evenly distributed around the circumference, and each connecting hole is sealed with a threaded plug 6.

[0024] According to the requirements, the external slip connector 1, the release handle 2, and the centering device 3 are all existing known technologies. During use, the external slip connector 1 is a high-strength coiled tubing connector, with the same inner diameter as the coiled tubing, enabling connection and locking with the coiled tubing, and possessing excellent tensile and torsional resistance. The release handle 2 is used when the tool string gets stuck; by pulling the coiled tubing or / and using a ball to press it down, the internal shear pin is sheared by upward lifting force or / and downward pushing force, thus disengaging the coiled tubing from the lower tool string. The bypass short section 5 is used to interchange between two methods: leak detection in the annulus alone and leak detection simultaneously in the coiled tubing and the annulus. When the plug 6 is not installed on the short section 5, the coiled tubing and the casing above the packer are connected, and pressure can be applied through the coiled tubing to achieve pressure build-up in the annulus above the packer. After the plug 6 is installed, the coiled tubing and the casing above the packer are not connected. After pressure build-up in the annulus, pressure is applied to the upper part of the packer, and the pressure from the coiled tubing is transmitted to the lower casing of the packer to build up pressure, simultaneously performing pressure build-up and leak detection on the upper and lower parts of the packer. The coupling locator 4 can accurately calibrate the tool string depth. The seeker 7 is connected to the bottom of the entire tool string to guide the tool string smoothly into the well.

[0025] This invention provides a tool that combines the advantages of long packer life, small tool size, short track changing stroke, fast setting speed, and simultaneous leak detection above and below the packer. It improves leak detection efficiency, reduces construction complexity, shortens the construction cycle, meets low-cost and environmental protection requirements, and achieves high-efficiency treatment of damaged wells in oilfields. The invention has a reasonable and compact structure, is easy to use, and features safety, labor-saving, simplicity, and high efficiency.

[0026] The above-mentioned oilfield casing leak detection tools can be further optimized and / or improved according to actual needs: As attached Figure 1 , 2As shown in Figures 3 and 4, the packer includes a central tube 10, a track rod 11, a rubber sleeve 12, a friction block 13, a spring 14, a slip 15, and a pin 16. An upper connector 17 is fixedly installed between the upper end of the central tube 10 and the lower end of the bypass short section 5. The lower end of the central tube 10 is fixedly installed together with the upper end of the hollow track rod 11. An outer ring platform 26 is fixedly installed on the lower outer side of the central tube 10. Several internally and externally communicating internal liquid outlet holes 22 are evenly distributed along the circumference of the outer ring platform 26. A cone 21 is fitted onto the outer side of the outer ring platform 26. The lower outer side of the cone 21 has a conical surface that is larger at the top and smaller at the bottom. An adjusting ring 20 is fixedly installed on the upper outer side of the cone 21. The upper part of the adjusting ring 20 sits on the upper surface of the outer ring platform 26, corresponding to the adjusting ring 20. The cone 21 at position 0 has several radially penetrating outflow liquid holes 37 evenly distributed along its circumference on the lower outer side. A rubber sleeve 12 is fitted onto the upper outer side of the central tube 10 at the upper end of the adjusting ring 20. A cone cap 19 is fixed to the upper outer side of the central tube 10 at the upper end of the rubber sleeve 12. A lower connector 18 is fixedly installed between the lower end of the track rod 11 and the upper end of the coupling locator 4. Several pairs of upward-opening V-shaped sliding grooves 28 are evenly distributed along the circumference on the lower outer side of the track rod 11 above the lower connector 18. A downward-opening V-shaped upper sliding groove 27 is provided on the outer side of the track rod 11 between each pair of adjacent sliding grooves 28. The upper part of each sliding groove 28 is connected to the lower part of the corresponding upper sliding groove 27. The track rod 11 has two outward-facing elongated slots 29 symmetrically arranged on the outer side of its middle section. The lower part of the two slots 29 is connected to the upper part of two symmetrically arranged upper sliding slots 27. A slide cylinder 23 is coaxially fitted on the outer side of the middle section of the track rod 11. Several mounting holes with internal and external connections are evenly distributed around the circumference of the upper outer side of the slide cylinder 23. A slip 15 is provided on the upper part of the slide cylinder 23 corresponding to each mounting hole. The inner side of the upper part of the slip 15 is inclined to match the outer side of the lower end of the cone 21. An L-shaped connecting block 24 is fixed at the lower end of each slip 15 and installed in the corresponding mounting hole. Two pins 16 are evenly distributed around the circumference of the lower part of the slide cylinder 23. The ends of the two pins 16 pass through the inner wall of the slide cylinder 23. Located below the two sliding grooves 28, a number of outward-facing mounting grooves 35 are evenly distributed along the circumference of the outer side of the middle part of the sliding cylinder 23, corresponding to the position between the lower part of the mounting hole and the upper part of the pin 16. A locking block 36 is fixed on the upper part of the sliding cylinder 23 corresponding to the position of each mounting groove 35. A mounting sleeve 25 is fixedly installed on the lower outer side of the sliding cylinder 23. A friction block 13 is installed in each mounting groove 35. An upper support block 8 and a lower support block 9 are fixed at the upper and lower ends of the friction block 13, respectively. An outward-facing arc-shaped spring piece 14 is installed between each friction block 13 and the inner wall of the mounting groove 35. The spring piece 14 causes the outer side of the upper support block 8 and the inner side of the locking block 36, as well as the outer side of the lower support block 9 and the inner side of the upper end of the mounting sleeve 25, to abut against each other.

[0027] According to the requirements, each friction block 13 has a slot on its inner side. The upper and lower ends of the spring piece 14 abut against the upper and lower parts of the slot, respectively. The middle part of the spring piece 14 abuts against the bottom wall of the mounting groove 35. The friction block 13, the upper support block 8 and the lower support block 9 are integrated. The slot block 36 and the slide cylinder 23 are integrated. The lower end of the upper slide groove 27 and the upper end of the lower slide groove 28 are flush. During use, after the central tube 10 is lowered into the sleeve, the friction block 13 rubs against the inner wall of the sleeve under the action of the spring piece 14. When the coupling locator 4 is positioned at the target position, the central tube 10 is rotated, so that the pin 16 enters the upper sliding groove 27 along the side of the lower sliding groove 28. By rotating the central tube 10 multiple times, the two pins 16 are rotated into the upper sliding groove 27 that communicates with the long groove 29, that is, the pins 16 are located at the lower part of the long groove 29. Then the central tube 10 is lowered, and the two pins 16 move upward relative to the central tube 10 to the upper part of the long groove 29. The pins 16 drive the sliding cylinder 23 to move upward relative to the central tube 10. The sliding cylinder 23 drives the slip 15 to move upward relative to the central tube 10 and contact the lower end of the cone 21. Under the action of the cone surface at the lower end of the cone 21, the slip 15 is pushed outward and closes to the sleeve. With the inner walls of the tubes pressed together, the slips 15 are fixed, thus limiting and fixing the slips 15, cone 21, and adjusting ring 20. As the central tube 10 continues to descend, the cone cap 19 continues to move downward under the action of the central tube 10. The lower end face of the cone cap 19 and the upper end face of the adjusting ring 20 approach each other, squeezing the rubber sleeve 12. The outer side of the rubber sleeve 12 protrudes outward and seals against the inner side of the casing, completing the setting process. After use, the central tube 10 is lifted, the cone cap 19 moves upward, and the rubber sleeve 12 returns to its original shape after being squeezed. At the same time, the cone 21 and slips 15 move away from each other, and the pin 16 moves relative to the central tube 10 from the long groove 29 to the upper sliding groove 27, and finally moves into the lower sliding groove 28, completing the unsealing process. This process can be repeated to achieve multiple setting and unsealing, improving the working efficiency of the packer in the well.

[0028] As attached Figure 4 As shown, the right side of the upper slide groove 27 and the right side of the lower slide groove 28 are both vertical surfaces. The lower inner side of each lower slide groove 28 and the upper part of each adjacent two lower slide grooves 28 have a smooth transition, as do the lower parts of any two adjacent upper slide grooves 27. According to requirements, the right side of the foremost upper slide groove 27 and the right side of the lower slide groove 28 are both vertical surfaces. The upper slide grooves 27 and lower slide grooves 28 in other positions have the same structure as the foremost upper slide grooves 27 and lower slide grooves 28 and are arranged circumferentially. During use, this arrangement allows the pin 16 to move smoothly within the upper slide groove 27, lower slide groove 28, and long groove 29, preventing collisions and jamming between the pin 16 and the track rod 11.

[0029] As attached Figure 3 , 4As shown, each sliding groove 28 has a radially penetrating first row of sand holes 30 at its lower part, and each long groove 29 extends to the inner side of the track rod 11 at its upper part. Each upper sliding groove 27 corresponding to the position between two long grooves 29 has a radially penetrating second row of sand holes 31 at its upper part. According to the requirements, the bottom wall of the upper part of each long groove 29 extends to the inner side of the track rod 11 in the radial direction. The two upper sliding grooves 27 connected to the long grooves 29 do not have a second row of sand holes 31 at their upper parts, while the other upper sliding grooves 27 have a second row of sand holes 31 at their upper parts. The cross-sections of the second row of sand holes 31 and the first row of sand holes 30 are both circular. The projection of the first row of sand holes 30 is tangent to the inner arc transition surface of the lower part of the sliding groove 28, and the projection of the second row of sand holes 31 is tangent to the inner arc transition surface of the upper part of the upper sliding groove 27. During use, this setting allows the movable pin 16 to be pushed into the inner side of the track rod 11 after fracturing sand enters the upper chute 27, lower chute 28 and long chute 29, preventing the pin 16 from getting stuck and causing the setting failure.

[0030] As attached Figure 1 , 2 As shown in Figures 3 and 4, each mounting groove 35 has a radially penetrating third row of sand holes 32 at its upper and lower parts. Correspondingly, the upper outer side of the track rod 11 above the sliding groove 27 has several internally and externally connected strip-shaped fourth row of sand holes 33 distributed at intervals along the circumference. Depending on the requirements, the third row of sand holes 32 is located at the upper and lower parts of the bottom wall of the mounting groove 35. Depending on the requirements, there are four fourth row of sand holes 33, with their upper ends located above the long groove 29. During use, this arrangement prevents fracturing sand from entering the inner side of the sliding cylinder 23 and the mounting groove 35, thus preventing the sliding cylinder 23 from moving smoothly up and down and causing the spring plate 14 to fail. The third row of sand holes 32 and the fourth row of sand holes 33 can discharge fracturing sand into the interior of the track rod 11, allowing the sliding cylinder 23 to move up and down while ensuring that the spring plate 14 always keeps the friction block 13 pressed against it, improving the success rate of the sealing operation.

[0031] As attached Figure 3 As shown, an inner annular groove 34 is provided on the inner side of the middle part of the rubber sleeve 12. During use, with this setting, when the cone cap 19 moves downward under the drive of the central tube 10, the slip 15 fixes the cone 21, and the cone cap 19 and the adjusting ring 20 simultaneously squeeze the rubber sleeve 12, the inner annular groove 34 causes the middle part of the rubber sleeve 12 to bulge outward and make sealing contact with the inner wall of the sleeve, increasing the sealing contact area between the rubber sleeve 12 and the inner wall of the sleeve and improving the setting efficiency.

[0032] As attached Figure 1As shown, the coupling locator 4 is a spring-loaded coupling locator 4. According to requirements, the coupling locator 4 is a known spring-loaded coupling locator 4, such as the spring-loaded coupling locator 4 with publication number CN104989384A. The coupling locator 4 relies on the elastic force of its own spring 14. When the coupling locating block passes through the casing coupling, due to the certain slope of the measuring protrusion, it will be engaged in the casing coupling groove and pulled out, forming a situation of being engaged and then disengaged. It can withstand pressure and will not cause positioning failure or drill jamming due to the presence of sand. Furthermore, the spring has sufficient elasticity and an extremely long lifespan. The weight indicator in the control room will display the weight changes during overlift and recovery, which can be used to accurately calibrate the tool string depth.

[0033] Example 2: As shown in the attached document Figure 1 , 2 As shown in Figures 3 and 4, a method for finding leaks in casing includes the following steps: First, connect the lower end of the coiled tubing to the upper end of the external slip connector 1 and lower it into the middle of the well, then record the initial position of the packer. The second step is to set the packer in the sleeve. The third step is to pump fluid into the annulus above the packer and the annulus below the packer, so that both the annulus above the packer and the annulus below the packer are pressurized. Fourth step: When the liquid pressure in both the annulus above and below the packer reaches the set value, stop the pump. Fifth, observe the rate of pressure drop in the casing annulus above and below the packer. Compare these rates with the standard pressure drop rate per unit time of the casing. When both rates are greater than the standard pressure drop rate per unit time, the pressure drop rate above the packer is considered normal. Both the casing below the packer and the casing below the packer have leaks. When the standard pressure drop rate per unit time of the casing is the same as the pressure drop rate of the fluid in the annulus of the casing below the packer and is less than the pressure drop rate of the fluid in the annulus of the casing above the packer, then only the casing above the packer has a leak. When the pressure drop rate of the fluid in the annulus of the casing above the packer is the same as the standard pressure drop rate per unit time of the casing and is less than the pressure drop rate of the fluid in the annulus of the casing below the packer, and the rates increase sequentially, then only the casing below the packer has a leak. Step 6: Determine the location of the leak.

[0034] The above-mentioned casing leak detection method can be further optimized and / or improved according to actual needs: As attached Figure 1 , 2 As shown, step six includes: (i) When the leak is only present in the casing above the packer, after unsealing the packer, raise the coiled tubing to a certain distance, and then repeat steps two through five. 1. If the leak is located in the sleeve below the packer, record the first position of the packer at this time to determine that the leak is located in the sleeve between the initial position and the first position of the packer; 2. If the leak is located on the casing above the packer, continue to unseal the packer and raise the coiled tubing to a certain distance and repeat steps 2 to 5 until the leak is determined to be located on the casing below the packer. Record the position of the packer at this time and the position of the packer when it was set last time. Determine that the leak is located on the casing between the current position of the packer and the position of the packer when it was set last time. 3 If the leaks are located on the sleeve above and below the packer, first record the second position of the packer at this time to determine that some leaks are located on the sleeve between the initial and second positions of the packer. Then, follow step 2 to determine the location of the remaining leaks. (ii) When the leak is only present in the casing below the packer, after unsealing the packer, lower the coiled tubing to a certain distance, and then repeat steps two through five. 1. If the leak is located on the sleeve above the packer, record the third position of the packer at this time to determine that the leak is located on the sleeve between the initial position and the third position of the packer; 2. If the leak is located in the casing below the packer, continue to unseal the packer and lower the coiled tubing to a certain distance and repeat steps 2 to 5 until the leak is determined to be located in the casing above the packer. Record the position of the packer at this time and the position of the packer during the previous setting. Determine that the leak is located in the casing between the current position of the packer and the position of the packer during the previous setting. 3 If the leaks are located on the sleeve above and below the packer, first record the fourth position of the packer at this time to determine that some leaks are located on the sleeve between the initial position and the fourth position of the packer. Then, follow step 2 to determine the location of the remaining leaks. (iii) When there are leaks in both the sleeve above the packer and the sleeve below the packer, determine the location of the leaks according to steps one and two respectively.

[0035] As attached Figure 1 , 2 As shown, after the location of the leak is determined, the sleeve with the leak is accurately located using the coupling locator 4.

[0036] The coupling locator 4 relies on the elastic force of its own spring bar. When the coupling locating block passes through the casing coupling, due to the certain slope of the coupling locating block, it will get stuck into the casing coupling groove and be pulled out, forming a situation of getting stuck and then getting stuck. It can withstand pressure and will not cause positioning failure or drill jamming due to the presence of sand. Moreover, the spring bar has sufficient elasticity and an extremely long service life. The weight indicator in the control room will show the weight changes during overlift and recovery, based on which the tool string depth can be accurately calibrated and the perforation layer can be accurately located.

[0037] When only leak detection is needed on the upper part of the casing, the following steps are included: First, connect the lower end of the coiled tubing to the upper end of the external slip connector 1 and lower it into the middle of the well, then record the initial position of the packer. The second step is to set the packer in the sleeve. The third step is to either pump fluid directly into the annulus above the packer, or remove plug 6 and pump fluid into the coiled tubing to pressurize the annulus above the packer. Fourth step: Once the liquid pressure in the annulus above the packer reaches the set value, stop the pump. Fifth, observe the rate of decrease of liquid pressure in the annulus above the packer and compare it with the standard rate of decrease of pressure per unit time in the casing. If the rate of decrease of liquid pressure in the annulus above the packer is greater than the standard rate of decrease of pressure per unit time in the casing, then there is a leak in the casing above the packer. Step six: After releasing the packer, raise the coiled tubing to a certain distance, then repeat steps two through five. 1. If the leak is located in the casing below the packer, record the fifth position of the packer at this time to determine that the leak is located in the casing between the initial position and the fifth position of the packer; 2. If the leak is located in the casing above the packer, continue to unseal the packer and raise the coiled tubing to a certain distance and repeat steps 2 to 5 until the leak is determined to be located in the casing annulus below the packer. Record the position of the packer at this time and the position of the packer when it was set last time. Determine that the leak is located in the casing between the current position of the packer and the position of the packer when it was set last time. 3 If the leaks are located on the sleeve above and below the packer, first record the sixth position of the packer at this time to determine that some leaks are located on the sleeve between the initial position and the sixth position of the packer. Then, follow step 2 to determine the location of the remaining leaks. Step 7: After determining the location of the leak, accurately locate the sleeve with the leak using the coupling locator 4.

[0038] When checking for leaks in the casing above the packer, in the third step, cleaning fluid can be injected into the coiled tubing (with plug 6 installed). The cleaning fluid enters the casing annulus below the packer through the coiled tubing and tool string to clean the casing below the packer, allowing for simultaneous flushing and leak checking.

[0039] The set value of the liquid pressure in the annulus above the packer or the liquid pressure in the annulus above the packer is less than 20 MPa, reducing operational risks.

[0040] This invention improves the traditional packer top leak detection technology by simultaneously pressurizing the packer from top to bottom, thereby synchronously locating leaks in the casings above and below the packer. This greatly saves operating time and costs, reduces unnecessary expenses, and overcomes the shortcomings of traditional leak detection methods, such as long construction period, high cost, and low accuracy.

[0041] With the increasing number of horizontal wells in oilfield development, the demand for casing damage well management has also increased. However, current leak detection tools suffer from low efficiency, high safety risks, and high construction costs. Successful research into oilfield casing leak detection technology will provide more scientific, efficient, and professional tools for oilfield well workover operations. Addressing the issues of leak points or leak sections in Xinjiang oilfields, the development of oilfield casing leak detection tools will enable rapid, accurate, safe, and efficient location of leak sections while eliminating damage to the formation and casing. This meets the requirement of "single-well safety, speed, and efficiency improvement," supporting the economical and efficient development of Xinjiang oilfields and further ensuring the steady progress of reserve and production increases in the Junggar Basin; its application prospects are broad.

[0042] The casing leak detection tool has been used multiple times in Xinjiang Oilfield. It has been successfully implemented in many wells with casing damage, such as development wells and horizontal wells of Xinjiang Oilfield Development Company and Baikouquan Oil Production Plant. The invention has been successfully applied to 6 wells, including MaHW, with a leak detection success rate of up to 100%, and all can be accurate to within 15m.

[0043] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method for leak detection in oilfield casing, characterized in that... Includes the following steps: The first step is to connect the lower end of the coiled tubing to the upper end of the external slip connector and lower it into the middle of the well, then record the initial position of the packer. The second step is to set the packer in the sleeve. The third step is to pump fluid into the annulus above the packer and the annulus below the packer, so that both the annulus above the packer and the annulus below the packer are pressurized. Fourth step: When the liquid pressure in both the annulus above and below the packer reaches the set value, stop the pump. Fifth, observe the rate of pressure drop in the casing annulus above and below the packer. Compare these rates with the standard pressure drop rate per unit time of the casing. When both rates are greater than the standard pressure drop rate per unit time, the pressure drop rate above the packer is considered normal. Both the casing below the packer and the casing below the packer have leaks. When the standard pressure drop rate per unit time of the casing is the same as the pressure drop rate of the fluid in the annulus of the casing below the packer and is less than the pressure drop rate of the fluid in the annulus of the casing above the packer, then only the casing above the packer has a leak. When the pressure drop rate of the fluid in the annulus of the casing above the packer is the same as the standard pressure drop rate per unit time of the casing and is less than the pressure drop rate of the fluid in the annulus of the casing below the packer, and the rates increase sequentially, then only the casing below the packer has a leak. Step 6: Determine the location of the leak; Step six includes: (i) When the leak is only present in the casing above the packer, after unsealing the packer, raise the coiled tubing to a certain distance, and then repeat steps two through five.

1. If the leak is located in the sleeve below the packer, record the first position of the packer at this time to determine that the leak is located in the sleeve between the initial position and the first position of the packer; 2. If the leak is located on the casing above the packer, continue to unseal the packer and raise the coiled tubing to a certain distance and repeat steps 2 to 5 until the leak is determined to be located on the casing below the packer. Record the position of the packer at this time and the position of the packer when it was set last time. Determine that the leak is located on the casing between the current position of the packer and the position of the packer when it was set last time. 3 If the leaks are located on the sleeve above and below the packer, first record the second position of the packer at this time to determine that some leaks are located on the sleeve between the initial and second positions of the packer. Then, follow step 2 to determine the location of the remaining leaks. (ii) When the leak is only present in the casing below the packer, after unsealing the packer, lower the coiled tubing to a certain distance, and then repeat steps two through five.

1. If the leak is located on the sleeve above the packer, record the third position of the packer at this time to determine that the leak is located on the sleeve between the initial position and the third position of the packer; 2. If the leak is located in the casing below the packer, continue to unseal the packer and lower the coiled tubing to a certain distance and repeat steps 2 to 5 until the leak is determined to be located in the casing above the packer. Record the position of the packer at this time and the position of the packer during the previous setting. Determine that the leak is located in the casing between the current position of the packer and the position of the packer during the previous setting. 3 If the leaks are located on the sleeve above and below the packer, first record the fourth position of the packer at this time to determine that some leaks are located on the sleeve between the initial position and the fourth position of the packer. Then, follow step 2 to determine the location of the remaining leaks. (iii) When there are leaks in both the sleeve above the packer and the sleeve below the packer, determine the location of the leaks according to steps one and two respectively. The oilfield casing leak detection tool used in this oilfield casing leak detection method includes an external slip connector, a release handle, a centralizer, a bypass stub, a packer, a coupling locator, and a guide head, which are fixedly installed together from top to bottom. The lower outer side of the bypass stub has several interconnecting holes that are evenly distributed around the circumference, and each interconnecting hole is sealed with a threaded plug. The packer includes a central tube, a track rod, a rubber sleeve, friction blocks, springs, slips, and pins. An upper connector is fixedly installed between the upper end of the central tube and the lower end of the bypass section. The lower end of the central tube is fixedly installed together with the upper end of the hollow track rod. An outer ring platform is fixed to the lower outer side of the central tube. Several internally and externally communicating liquid outlets are evenly distributed along the circumference of the outer ring platform. A cone is fitted onto the outer side of the outer ring platform. The lower outer side of the cone has a tapered surface that is wider at the top and narrower at the bottom. An adjusting ring is fixedly installed on the upper outer side of the cone. The upper part of the adjusting ring sits on the upper surface of the outer ring platform. The lower outer side of the cone, corresponding to the position below the adjusting ring, is positioned along... Several radially penetrating outflow liquid holes are evenly distributed around the circumference. A rubber sleeve is fitted on the outer side of the upper part of the central tube corresponding to the upper end of the adjusting ring. A conical cap is fixed on the outer side of the upper part of the central tube corresponding to the upper end of the rubber sleeve. A lower connector is fixedly installed between the lower end of the track rod and the upper end of the coupling positioner. Several pairs of upward-opening V-shaped sliding grooves are evenly distributed around the outer side of the lower part of the track rod above the lower connector. A downward-opening V-shaped upper sliding groove is provided on the outer side of the track rod between every two adjacent sliding grooves. The upper part of each sliding groove is connected to the lower part of the corresponding upper sliding groove. Two outward-opening elongated slots are symmetrically arranged on the outer side of the section. The lower part of the two slots is connected to the upper part of two symmetrically arranged upper sliding slots. A sliding cylinder is coaxially fitted on the outer side of the middle section of the track rod. Several internally and externally connected mounting holes are evenly distributed along the circumference of the upper outer side of the sliding cylinder. A slip is provided on the upper part of the sliding cylinder corresponding to each mounting hole. The inner side of the upper part of the slip is inclined to match the outer side of the lower end of the cone. An L-shaped connecting block is fixed at the lower end of each slip and installed in the corresponding mounting hole. Two pins are evenly distributed along the circumference of the lower part of the sliding cylinder. The ends of the two pins pass through the inner wall of the sliding cylinder. Located at the lower part of the two sliding grooves, a number of outward-facing mounting grooves are evenly distributed along the circumference of the outer side of the middle part of the sliding cylinder between the position below the mounting hole and above the pin. A locking block is fixed to the upper part of the sliding cylinder corresponding to each mounting groove position, and a mounting sleeve is fixedly installed on the lower outer side of the sliding cylinder. A friction block is installed in each mounting groove. An upper support block and a lower support block are fixed to the upper and lower ends of the friction block, respectively. An outward-facing arc-shaped spring is installed between each friction block and the inner wall of the mounting groove. The spring makes the outer side of the upper support block and the inner side of the locking block, as well as the outer side of the lower support block and the inner side of the upper end of the mounting sleeve, abut against each other.

2. The oilfield casing leak detection method according to claim 1, characterized in that... The right side of the upper slide groove and the right side of the lower slide groove are both vertical surfaces. The inner side of the lower part of each lower slide groove and the upper part of each two adjacent lower slide grooves are smoothly transitioned. The lower part of each two adjacent upper slide grooves is also smoothly transitioned.

3. The oilfield casing leak detection method according to claim 1 or 2, characterized in that... Each sliding groove has a first row of sand holes that penetrate radially at the bottom, and each long groove extends to the inside of the track rod at the top. Each upper sliding groove corresponding to the position between two long grooves has a second row of sand holes that penetrate radially at the top.

4. The oilfield casing leak detection method according to claim 2, characterized in that... The inner side of the middle part of the rubber tube is provided with an inner ring groove; or / and, the coupling positioner is a spring-loaded coupling positioner.

5. The oilfield casing leak detection method according to claim 3, characterized in that... The inner side of the middle part of the rubber tube is provided with an inner ring groove; or / and, the coupling positioner is a spring-loaded coupling positioner.

6. The oilfield casing leak detection method according to claim 1, characterized in that... Once the leak location is determined, the sleeve with the leak can be accurately located using the coupling locator.

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