Well repair tool, drilling tool and fish salvaging method

Abstract

The invention provides a workover tool, a drilling tool and a fish salvaging method, the workover tool comprises a milling head, a milling pipe, a salvaging piece, a circulating joint, a two-stage buckling joint and a safety joint, an upper end pipe opening of the milling pipe is connected with the two-stage buckling joint, and a lower end pipe opening of the milling pipe is connected with the milling head; the circulating joint is positioned in the milling pipe and is connected with the two-stage buckling joint; the working end of the salvage piece faces the lower end of the milling pipe, and the salvage piece and the lower end of the milling pipe are spaced by a certain distance; the safety connector is located at the upper end of the two-stage buckling connector. The drilling tool comprises the well repairing tool. The salvage method is realized by using the drilling tool. The well repairing tool can be applied to different occasions for casing milling and fishing, and the practicability is high; the combined drilling tool is high in fishing efficiency; by means of the fishing method, milling and fishing can be completed at a time, and the operation efficiency is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of oil well workover, and specifically, to a workover tool, a drill string, and a method for fishing a sunken fish Background Art

[0002] After an oil and gas well has been exploited for a period of time, various fluids in the formation enter the well and form certain scale deposits. At the same time, due to the long-term stillness of the working fluid in the well, a large amount of sediment is formed. The scale deposits seriously affect the exploitation effect, and the sediment causes some tubing strings to be buried; after unstable rocks such as shale and coal in the open hole section of the formation collapse, the tubing string will also be buried. In any of the above situations, a workover operation is required. Currently, the commonly used method is to first use a milling pipe to mill the sleeve, and then use a reverse-threaded large-head male taper to stop the pump and reverse the buckle for fishing from the tubing collar

[0003] In the actual operation of fishing with a reverse-threaded large-head male taper while stopping the pump, the following situations often occur: The first situation is that occasionally, a milling head or a milling pipe falls into the well, causing the well to be abandoned; the second situation is that when fishing while stopping the pump, the fluid in the well enters the wellbore, causing a well control risk, so a kill operation is required. The kill operation will press the impurities in the wellbore into the formation, causing the oil and gas channels to be blocked and seriously affecting the subsequent exploitation effect; the third situation is that only the collar is fished out. Therefore, only a reverse-threaded female taper can be lowered to make a thread for fishing. After making a thread with the reverse-threaded female taper, the tubing string may be buried, and the fishing drill string has to be withdrawn from the safety joint in the fishing string. It is necessary to re-lower the milling pipe for milling operation and then lower the fishing string to engage and fish again. The repeated operation in a cycle causes the workover operation cycle and the workover cost to increase infinitely, and at the same time, it greatly delays the re-exploitation operation of the oil and gas well; the fourth situation is that the water eye of the tubing string after fishing is blocked, and the drill string cannot be circulated to spray drilling fluid, resulting in waste of drilling fluid, increasing the environmental protection pressure and the tripping speed; the fifth situation is that when fishing while stopping the pump, unstable rocks such as shale and coal in the open hole section of the formation collapse, causing stuck pipe due to collapse, and the fishing drill string has to be withdrawn from the safety joint in the fishing string. The subsequent treatment method is the same as that of the third situation. Using the commonly used fishing method has low fishing efficiency and is prone to accidents

[0004] The Chinese patent application with the publication number of "CN106869849A" and the name of "Integrated Milling and Fishing Tool and Its Fishing Operation Method" discloses an integrated milling and fishing tool. The tool includes an upper joint, a threading and fishing part, and a milling part connected in sequence from top to bottom, and can complete milling, threading, and fishing operations in one trip. However, the disclosed patent does not have components such as a lengthened milling head and a circulation joint, and there are still problems such as the milling and fishing components falling into the well, and the fishing effect needs to be optimized

[0005] Therefore, it is of great significance to study a milling and fishing method that optimally integrates the two-trip operations of milling and fishing into one trip under the state of continuously pumping throughout the process and has a good fishing effect Summary of the Invention

[0006] The object of the present invention is to solve at least one of the above-mentioned deficiencies existing in the prior art. For example, one object of the present invention is to provide a workover tool integrating the functions of over-milling and fishing. Another example is to provide a drill string combined with over-milling and fishing. Another object of the present invention is to provide an efficient method for fishing a fish

[0007] To achieve the above object, on the one hand, the present invention provides a workover tool, which may include a milling head, a milling pipe, a fishing piece, a circulation joint, a double-stage coupling joint and a safety joint. Among them, the upper end pipe orifice of the milling pipe is connected to the double-stage coupling joint, and the lower end pipe orifice is connected to the milling head; the circulation joint is located inside the milling pipe and is connected to the double-stage coupling joint; the fishing piece faces the lower end of the milling pipe, and the tool end of the fishing piece is spaced a certain distance from the lower end of the milling pipe; the safety joint is located at the upper end of the double-stage coupling joint.

[0008] According to one or more exemplary embodiments of one aspect of the present invention, the fishing piece may include a male taper or a female taper, and the fishing piece is arranged along the central axis direction of the milling pipe.

[0009] According to one or more exemplary embodiments of one aspect of the present invention, when the fishing piece is a male taper, the taper of the male taper may be 1:20, with 20 teeth per inch and a thread depth of 1.9 mm.

[0010] According to one or more exemplary embodiments of one aspect of the present invention, a double-male short joint may be provided between the milling head and the milling pipe.

[0011] According to one or more exemplary embodiments of one aspect of the present invention, a back-pressure valve may be provided at the lower end of the circulation joint.

[0012] According to one or more exemplary embodiments of one aspect of the present invention, the milling head may include an extended milling head, and the extended milling head includes a serrated extended milling head, and the serrated extended milling head is connected to the milling pipe through a double-male short joint.

[0013] On the other hand, the present invention provides a drill string, which may include a fishing cup, a drill collar, a heavy drill pipe, a drill pipe and the workover tool described in the above exemplary embodiments. Among them, the fishing cup, the drill collar, the heavy drill pipe and the drill pipe are arranged above the workover tool in sequence from bottom to top.

[0014] In another aspect, the present invention provides a method for fishing a fish left in the well. The fishing method can use the drill string described above for fishing, and the fishing method may include the following steps: Assemble the drill string and lower the drill string to a position 0.5 - 1.0 m above the fish top of the fish left in the well, and flush the fish top; respectively test the rotation torque and static hook load during lifting and lowering in both the states of pumping and stopping the pump; start pumping, slowly lower the drill string to probe the fish head; lift the drill string, and according to the results of the above tests, rotate the drill string and adjust the over-milling parameters; lower the drill string to perform over-milling fishing; pull out the drill string, complete the inspection and clean the fishing cup, pour out the fish left in the well, continue to lower the drill string for over-milling fishing after detecting the combined tool until the over-milling and fishing tasks are completed.

[0015] According to one or more exemplary embodiments of another aspect of the present invention, the over-milling parameters can be adjusted as follows: the rotation speed is 30 - 50 RPM; the no-load torque is +3 KN·m, and the total torque is less than 10 KN·m / s; the drilling pressure is 10 - 20 KN.

[0016] According to one or more exemplary embodiments of another aspect of the present invention, when the fishing piece enters the water eye of the fish left in the well, if the over-milling parameters are abnormal during the over-milling process, the over-milling can be immediately stopped, the drill string can be lifted, the cause of the abnormality can be analyzed and processed, and after the abnormal problem is solved, continue to lower the drill string.

[0017] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0018] (1) The total length of the workover tool structure provided by the present invention can be adjusted according to the drilling rig, workover rig type and specific downhole conditions, and can be used for over-milling fishing in different occasions, with strong practicability;

[0019] (2) The combined drill string provided by the present invention has high fishing efficiency, and the relevant structure fished up is complete, avoiding the losses caused by repeated fishing operations;

[0020] (3) The fishing method provided by the present invention can optimize the over-milling and fishing into one-time completion, optimizing the operation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Through the following description in conjunction with the drawings, the above and other objects and / or features of the present invention will become clearer, wherein:

[0022] Figure 1 The schematic structural diagram of the workover tool according to an exemplary embodiment of the present invention is shown.

[0023] Description of the reference numerals:

[0024] 1 - milling head, 2 - milling pipe, 3 - double-stage coupling joint, 4 - safety joint, 5 - fishing piece, 6 - back-pressure valve, 7 - circulation joint, 8 - double-male nipple. DETAILED DESCRIPTION OF THE INVENTION

[0025] In the following, a workover tool, a drill string and a method for fishing a sunken fish will be described in detail in conjunction with the accompanying drawings and exemplary embodiments.

[0026] It should be noted that "first", "second", "third", etc. are only for convenience of description and easy distinction, and cannot be understood as indicating or implying relative importance. "Upper", "lower", "inner", "outer", etc. are only for convenience of description and to form a relative orientation or positional relationship, and do not indicate or imply that the component referred to must have that specific orientation or position.

[0027] First Exemplary Embodiment

[0028] This exemplary embodiment provides a workover tool.

[0029] Figure 1 The structural schematic diagram of a milling fishing combination workover tool according to an exemplary embodiment of the present invention is shown. The following will be combined with Figure 1 to describe the milling fishing combination workover tool of this exemplary embodiment. It should be noted that the direction from top to bottom described in the specification is the Figure 1 direction from left to right in

[0030] In this exemplary embodiment, as shown in Figure 1 , the workover tool mainly includes a milling head 1, a milling pipe 2, a fishing piece 5, a circulation joint 7, a double-stage coupling joint 3 and a safety joint 4. Among them, the milling head 1 is provided at the lower end of the milling pipe 2, and the double-stage coupling joint 3 is provided at the upper end of the milling pipe 2. The circulation joint is located inside the milling pipe and the upper end of the circulation joint is connected to the double-stage coupling joint. For example, threaded connection. The fishing piece 5 is arranged inside the milling pipe 2 and is at a certain distance from the orifice of the milling pipe 1. It is beneficial for the fishing piece 5 inside the workover tool to smoothly enter the fish eye for fishing. The safety joint 4 is located at the upper end of the double-stage coupling joint 3. A threaded connection can also be adopted between the safety joint 4 and the double-stage coupling joint 3.

[0031] In this exemplary embodiment, the fishing piece may include a male taper or a female taper. As shown in Figure 1As shown in the figure, the fishing tool 5 can be arranged in the central axis direction of the milling pipe 2. When the drill pipe body is broken, a female taper tap can be used for fishing; when the top end of the drill pipe string is a joint or a thickened part, a male taper tap can be used for fishing; when the tubing string is a coupling, a male taper tap can also be used for fishing. The taper of the male taper tap can be 1:20, with 20 threads per inch and a thread depth of 1.9 mm. The common taper of the male taper tap is 1:16. Compared with the common male taper tap, the male taper tap of this application has higher strength and is not easily broken during the process of making a hole. Moreover, the number of threads made during threading is more than that of the common male taper tap within the unit size, and the fish caught is more firmly held, resulting in a higher fishing success rate. The taper of the female taper tap can also be 1:20. Compared with the common female taper tap, the female taper tap is easier to fish for abnormal fish. In addition, the fishing tool can be connected to a slip socket. When using the slip socket, the other structures of the workover tool do not need to be adjusted, and the fishing method of the slip socket can be adopted.

[0032] In the present exemplary embodiment, as Figure 1 shown in the figure, a double male sub 8 can be arranged between the milling head 1 and the milling pipe 2 for connection. The double male sub can include a special high-strength double male sub, making the connection strength between the milling pipes higher. And the arranged double male sub 8 can be replaced for each trip of drilling to ensure safety after being lowered into the well. Correspondingly, the connection end between the milling pipe 2 and the milling head 1 can also be adjusted to a double female thread to facilitate connection with the double male sub 8. In addition, according to specific construction requirements, the number of milling pipes 2 can be increased to increase the length of the milling pipes lowered into the well. For example, one milling pipe 2 and one double male sub 8 can be used as an increasing unit, and the connection quantity of the increasing unit can be adjusted according to specific construction requirements. Further, if the fish in the well is buried by the sediment of drilling fluid or workover fluid, the connection length of the milling pipes can be increased by a longer distance according to requirements.

[0033] In the present exemplary embodiment, as Figure 1 shown in the figure, a back pressure valve 6 can be arranged at the lower end of the circulating sub.

[0034] In the present exemplary embodiment, the milling head 1 can include an extended milling head, and the extended milling head can include a serrated extended milling head, with higher milling efficiency. As Figure 1 shown in the figure, the milling head 1 and the milling pipe 2 can be connected through at least one group of double male subs 8. The extended milling head can include a milling head formed by integrating the milling head and a short milling pipe (the length is generally about 1 m). Such a milling head has been prepared by the manufacturer, and its precision, strength, anti-abrasion property, etc. are all better than those of the milling head processed on the construction site. The risk of the milling head (milling ring) falling into the well during on-site welding, which may cause the well to be scrapped, can be avoided.

[0035] Second Exemplary Embodiment

[0036] The present exemplary embodiment provides a drill string.

[0037] In this exemplary embodiment, the drill string mainly includes a fishing cup, a drill collar, a heavy drill pipe, and a workover tool as described in the first exemplary embodiment. Among them, the fishing cup, the drill collar, the heavy drill pipe, and the drill pipe are sequentially arranged at the upper end of the workover tool from bottom to top.

[0038] Third Exemplary Embodiment

[0039] This exemplary embodiment provides a method for fishing a fish downhole.

[0040] In this exemplary embodiment, the above-mentioned drill string in the second exemplary embodiment is used for fishing, and the fishing method mainly includes the following steps:

[0041] S1: Assemble the drill string and check the well depth, and circulate for 1.5 - 2.0 circulation periods to remove the afterflow completely. Here, circulation can refer to the process in which the surface drilling fluid, under the pressure of the drilling pump, passes through the assembled downhole drill string (fishing, dealing with complexity, drilling, core drilling), reaches the bottom of the well, and then returns to the surface along the annulus between the drill string and the wellbore. Here, the purpose of circulation can include circulating the gas or liquid generated and rising after the circulation in the well stops through the water eye of the drill string to prevent well control risks and avoid overflow or blowout incidents.

[0042] S2: Start the pump and slowly lower the drill string to a position 0.5 - 1.0 m above the theoretical predetermined position, such as 0.6 m, 0.7 m, or 0.9 m, and wash the fish top with a large displacement for 5 - 10 min. For example, 6 min, 7 min, or 9 min, to facilitate cleaning the sediment above the fish top and fishing the fish downhole.

[0043] S3: Test and record the parameters of the pick-up, lower, rotation torque, pick-up, lower, and static hook load respectively.

[0044] S4: Stop the pump and test and record the parameters of the pick-up, lower, rotation torque, pick-up, lower, and static hook load respectively.

[0045] Here, the purpose of testing the pick-up, lower, etc. data respectively in the states of non-stop pump and stop pump can include recording the basic data for the fishing operation and judging whether the tool has successfully fished the fish downhole after performing the fishing operation. For example, if the original basic hook load is 1000 KN, and the hook load after fishing is 1050 KN or the hook load after fishing is greater than 1000 KN, it means that the fish downhole has been successfully fished. That is, as long as the increase in the hook load after fishing is detected, it can be judged that the fish downhole has been successfully fished. In addition, the execution order of the non-stop pump detection and stop pump detection in S3 and S4 can be determined according to the downhole situation.

[0046] S5: Slowly lower the drill string to detect the fish head of the sunken fish. Here, the inside of the drill string of this application is unobstructed before entering the well. Whether the inside of the sunken fish pipe is unobstructed has nothing to do with the actual well depth of detecting the sunken fish. Taking the actual detected well depth as the standard, the purpose of measuring the theoretical fish head well depth is to provide a reference value. Usually, after the drill string assembly entering the well changes, the detected well depth will also change correspondingly. Lift the drill string, rotate the drill string according to the test results in S3 and S4, and adjust the over-milling parameters to determine the actual fish head well depth, providing data for subsequent over-milling and / or integrated over-milling and fishing operations. In addition, when the sum of the outer diameters of fishing tools such as a male taper and the outer diameter of the fish head is less than the wellbore diameter, usually when it exceeds the theoretical fish head well depth by 3m, it is necessary to slowly detect the fish head well depth.

[0047] S6: Lower the drill string and perform over-milling according to the distance from the milling head to the bottom of the fishing piece. Over-mill until the fishing piece enters the fish eye of the sunken fish. When the torque increases to a certain value and then quickly drops to the over-milling torque value, it indicates that the button has been made and the back-off is successful. Without stopping the top drive or the rotary table, lift the drill string and move it up and down. After circulating for 1.5 - 2.0 circulation cycles (fixed-point circulation is strictly prohibited), and meeting the well control safety requirements, then lift out the fishing drill string, unload the sunken fish and throw it to the site, and the fishing is over. Here, there may be accumulated fluids (gas or liquid) at the bottom or other parts of the sunken fish after the back-off is successful. Fluids in the rock formations of the formation enter the wellbore. If they are not circulated out of the ground, during a single round trip operation, these fluids will slip upward in the wellbore, which may cause well exploration accidents.

[0048] In this exemplary embodiment, the preset values of the drill string parameters may include: the rotation speed is 30 - 50 RPM; the no-load torque is +3 KN·m, and the total torque is less than 10 KN·m; the drilling pressure is 10 - 20 KN. In addition, due to different well depths, wellhead qualities, and wellbore trajectory designs in different wells, the torque may be determined according to the actual construction situation. For example, for some wells with relatively shallow depths (several hundred meters or more than one thousand meters), good wellbore quality (no dogleg severity, well inclination about 1 degree), and a straight wellbore trajectory design, the torque is very small; vice versa. The displacement can also be determined according to the wellbore size. For example, the displacement of a 444.5 mm wellbore can reach 50 - 60 L / s, while the displacement of a 215.9 mm wellbore is only about 30 L / s.

[0049] In this exemplary embodiment, when the fishing piece enters the fish eye of the sunken fish, if the over-milling parameters are abnormal during the over-milling process, immediately stop over-milling, lift the drill string, analyze the cause of the abnormality and handle it, and continue to lower the drill string after the abnormal problem is solved.

[0050] In this exemplary embodiment, after the back-off is successful, according to the operation process, lift the drill string, increase the displacement and circulate for 1.5 - 2.0 circulation cycles, and then pull out of the well.

[0051] In this exemplary embodiment, after the fishing operation is completed, the fishing cup can be inspected and cleaned, and each component of the drill string can be checked. Check whether the drill string is in good condition according to the requirements of the downhole tool, and replace or repair the drill string. If the current fishing task is not completed, continue to repeat S1-S5 until the milling and fishing task is completed.

[0052] When using the combined drill string provided by the present application to repair the well and handle the fish of the downhole tubing string in Well Yingbei 1, 12 tubing strings (113.58 meters) have been successfully milled and fished 10 times, and no milling head has fallen into the well, no milling pipe has broken and fallen into the well, no well control accident, no collapse and sticking accident, and only the collar has been fished out or no fish has been found.

[0053] In summary, the advantages of the present invention may include at least one of the following:

[0054] (1) The workover tool provided by the present invention can continuously mill and fish under the condition of not stopping the pump, effectively avoiding the unstable factors that occur during fishing with the pump stopped, and further promoting the smooth exploitation of oil and gas.

[0055] (2) The workover tool provided by the present invention is provided with a serrated extended milling head and a double-male short joint, which can improve the milling efficiency and effectively avoid the milling ring falling into the well and causing the well to be scrapped.

[0056] (3) The milling pipes of the workover tool provided by the present invention are connected by double-male short joints between the milling pipe and the milling head and between the milling pipes, which can effectively avoid the risk of the milling pipe breaking at the male thread stress and falling into the well, causing the well to be scrapped.

[0057] (4) The workover tool provided by the present invention uses a circulation joint, which can realize full-circulation during milling and fishing, effectively avoiding the risks of well control and sticking.

[0058] (5) The workover tool provided by the present invention can use different fishing tools according to the actual situation of the fish, and fish from the theoretical predetermined water eye of the tubing by skipping the collar, and can fish out at least one tubing string each time, effectively avoiding the phenomenon that only the collar is fished out when using a large-head male taper.

[0059] (6) The structure of the workover tool provided by the present invention has the function of a guide tube, which is beneficial to the internal fishing parts of the tool to enter the fish water eye for threading and fishing.

[0060] (7) The drill string structure provided by the present invention can be flexibly replaced and adjusted downhole according to the usage situation or requirements, avoiding the risks such as wellbore scrapping.

[0061] (8) The fishing method provided by the present invention can realize the full-circulation of the drilling fluid, effectively avoiding the risks of well control and collapse and sticking.

[0062] Although a workover tool, a drill string and a method for fishing a fish left in a well of the present invention have been described above by combining exemplary embodiments and the accompanying drawings, those skilled in the art should understand that various modifications and changes can be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined by the claims.

Claims

1. A workover tool, characterized in that, The workover tool includes a milling head, a milling pipe, a fishing piece, a circulation joint, a double-stage coupling joint and a safety joint. Among them, The upper pipe orifice of the milling pipe is connected to the double-stage coupling joint, and the lower pipe orifice is connected to the milling head. The circulation joint is located inside the milling pipe and is connected to the double-stage coupling joint. The circulation joint is connected to the fishing piece. The working end of the fishing piece faces the lower end of the milling pipe, and there is a certain distance between the fishing piece and the lower end of the milling pipe. The safety joint is located at the upper end of the double-stage coupling joint.

2. The workover tool according to claim 1, wherein, The fishing piece includes a male taper or a female taper, and the fishing piece is arranged along the central axis direction of the milling pipe.

3. The workover tool according to claim 2, wherein When the fishing piece is a male taper, the taper of the male taper is 1:20, with 20 threads per inch and a thread depth of 1.9 mm.

4. The workover tool according to claim 1, wherein, A double-male short joint is arranged between the milling head and the milling pipe.

5. The workover tool according to claim 1, characterized in that, A back-pressure valve is arranged between the fishing piece and the circulation joint.

6. The workover tool according to claim 1, characterized in that, The milling head includes an extended milling head. The extended milling head includes a serrated extended milling head, and the serrated extended milling head is connected to the milling pipe through a double-male short joint.

7. A drilling tool, characterized in that, The drill string includes a fishing cup, a drill collar, a heavy drill pipe, a drill pipe and the workover tool according to any one of claims 1 to 6. Among them, the fishing cup, the drill collar, the heavy drill pipe and the drill pipe are sequentially arranged above the workover tool from bottom to top.

8. A method for fishing a fish left in the well, characterized in that, The fishing method is realized by using the drill string described in claim 7, and the fishing method includes the following steps: Assemble the drill string and lower the drill string to 0.5 - 1.0 m above the fish top of the fish that has fallen into the well, and flush the fish top. Test the rotation torque and static hook load during lifting and lowering in both the pump-on and pump-off states respectively. Turn on the pump and slowly lower the drill string to probe the fish head. Lift the drill string, and according to the results of the above tests, rotate the drill string and adjust the over-milling parameters. Lower the drill string to perform over-milling fishing. Pull out the drill string to complete the inspection and clean the fishing cup, pour out the fallen fish, and continue to lower the drill string for over-milling fishing after detecting the combined tool until the over-milling and fishing tasks are completed.

9. The fish fishing method according to claim 8, characterized in that The adjustment of the over-milling parameters includes: the rotation speed is 30 - 50 RPM; the no-load torque is +3 KN·m, and the total torque is less than 10 KN·m; the drilling pressure is 10 - 20 KN.

10. The fish fishing method according to claim 8, wherein, When over-milling and fishing until the fishing piece enters the water eye of the fallen fish, if the over-milling parameters are abnormal during the over-milling process, immediately stop over-milling, lift the drill string, analyze the cause of the abnormality and handle it, and continue to lower the drill string after the abnormal problem is solved.

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