Unfreezing method and unfreezing system for coiled tubing of horizontal well in case of jamming

Abstract

The invention relates to the technical field of coiled tubing operation, in particular to a horizontal well coiled tubing jam releasing method and system, and the method comprises the steps: in the sand washing and drilling and grinding operation of a horizontal well coiled tubing, when a wellhead loses back and a drilling tool is stuck, the displacement of a positive circulation coiled tubing is increased, the coiled tubing moves up and down to release the jam, and if the jam cannot be released, the displacement of the positive circulation coiled tubing is increased; liquid nitrogen is injected into an annular pump of the continuous pipe and the casing pipe, and meanwhile sand washing drilling and grinding liquid is injected into the continuous pipe through a pump until jam releasing operation is completed; in the process, if liquid nitrogen pump injection is overpressure, the pump is stopped, sand washing drilling and grinding liquid continues to be pumped into the continuous pipe till the phenomenon that the load tonnage of the continuous pipe rises or the oil and sleeve pressure difference is reduced occurs, then liquid nitrogen is continuously pumped into the annular space, and meanwhile the pump injection displacement of the continuous pipe is gradually reduced till the hanging load of the continuous pipe is basically normal; and then the displacement of the coiled tubing is increased and the coiled tubing is moved up and down until the jam releasing operation is completed. Through the jam releasing method and the jam releasing system, the problems of high jam releasing difficulty, long consumed time and high cost can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of coiled tubing operations, and in particular to a method and system for releasing a stuck coiled tubing in a horizontal well. Background Art

[0002] The development of unconventional oil and gas reservoirs at home and abroad mainly adopts the technical concept of "horizontal well + volume fracturing". Usually, the bridge plug segmented cluster fracturing process or the continuous pipe segmented cutting fracturing process is used for segmented sand fracturing to achieve full transformation of the reservoir. After the fracturing transformation is completed, the drainage stage often causes wellbore blockage due to sand production in the fracturing section and soluble bridge plug residues, which affects the production of oil and gas wells. Generally, the wellbore needs to be cleaned by sand flushing or drilling and grinding. Compared with the wellbore cleaning operation of conventional oil pipes, the construction period of using continuous pipes for wellbore cleaning operations is short, and there is basically no well control and environmental protection risk during the whole process of pressure operation. Therefore, in the development of unconventional oil and gas fields, continuous pipes are often used for sand flushing or drilling and grinding operations at home and abroad.

[0003] In the sand flushing or drilling and grinding operations, drill stuck accidents often occur due to factors such as casing abnormalities, tool or equipment failure, sand flushing and drilling fluid leakage, and improper operation of personnel. Compared with conventional oil pipes, continuous pipes have the characteristics of small diameter and low strength. When the continuous pipe is stuck during sand flushing or drilling and grinding, the fracturing sand or drill cuttings in the wellbore near the stuck point cannot be effectively increased by pumping displacement to carry out the wellbore through the casing annulus. At the same time, it is difficult to unblock the continuous pipe by low-tonnage activities, and rashly lifting it with large tonnage can easily cause the continuous pipe to break and fall off the well, further complicating the accident. At present, the only treatment method is through-hole salvage, that is, cutting the pipe, casing milling, sand flushing, and salvage. The unblocking treatment is often difficult, time-consuming, and costly. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a method and system for releasing stuck coiled tubing in a horizontal well, which can effectively solve the problems of high difficulty, long time consumption and high cost in releasing stuck coiled tubing.

[0005] The present invention is achieved by adopting the following technical solutions: A method for releasing a stuck coiled tubing in a horizontal well, comprising the following steps: Step S 1 . When the wellhead is lost and the drill is stuck, increase the displacement of the positive circulation coiled tubing and unblock the upper and lower movable coiled tubing. If the unblocking is not possible, proceed to step S 2 ; Step S 2. Pump liquid nitrogen into the annulus between the coiled tubing and the casing, and at the same time pump sand flushing and drilling liquid into the coiled tubing until the jam-free operation is completed; during this process, if the liquid nitrogen pumping is over-pressured, stop the pump, and continue to pump sand flushing and drilling liquid into the coiled tubing until the coiled tubing load tonnage increases or the oil-casing pressure difference decreases, then continue to pump liquid nitrogen into the annulus, and at the same time gradually reduce the pumping displacement of the coiled tubing until the suspended weight of the coiled tubing is basically normal; then increase the displacement of the coiled tubing and move the coiled tubing up and down until the jam-free operation is completed.

[0006] Before pumping sand flushing and drilling fluid into the coiled tubing, press down the coiled tubing to put it in a compressed state.

[0007] The overpressure specifically refers to exceeding a preset overpressure protection value, and the overpressure protection value is lower than the casing limit pressure.

[0008] During the liquid nitrogen pumping process, liquid nitrogen is pumped into the annulus until the pressure value gradually tends to a stable value; if the pressure value of the liquid nitrogen in the annulus decreases by more than 5MPa, liquid nitrogen is continued to be pumped into the annulus to maintain the pressure value at a stable value.

[0009] During the unblocking operation, if the pressure difference between oil and casing increases, increase the pumping rate of the coiled tubing.

[0010] A horizontal well coiled tubing stuck release system comprises a liquid nitrogen pumping device and a sand flushing drilling and grinding liquid pumping device. The liquid nitrogen pumping device is used to pump liquid nitrogen into the annulus between the coiled tubing and the casing, and the sand flushing drilling and grinding liquid pumping device is used to pump sand flushing drilling and grinding liquid into the coiled tubing while pumping liquid nitrogen.

[0011] The liquid nitrogen pumping equipment comprises a liquid nitrogen source, a first connecting pipe and a first return valve which are connected in sequence, and the other end of the first return valve is connected to the annulus of the continuous pipe and the casing; the first connecting pipe is also provided with a liquid nitrogen pump truck and a first plug valve; the sand washing and drilling and milling liquid pumping equipment comprises a sand washing and drilling and milling liquid storage tank and a second connecting pipe which are connected in sequence, and the other end of the second connecting pipe is connected to the continuous pipe, and the second connecting pipe is also provided with a pump truck and a second plug valve.

[0012] It also includes a third connecting pipe, on which a third plug valve is also provided, and on which a fourth plug valve is also provided. One end of the third connecting pipe is connected to the first connecting pipe between the first plug valve and the first return valve, and the other end is connected to the second connecting pipe between the fourth plug valve and the second plug valve.

[0013] The second connecting pipe is also provided with a filter.

[0014] It also includes a second return valve, a blowdown throttling manifold and a sand settling tank which are connected in sequence; the second return valve and the continuous pipe are connected with the annulus of the casing; the other end of the sand settling tank is connected with the sand flushing and drilling liquid storage tank through a fourth connecting pipe.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the present invention, liquid nitrogen is pumped into the annulus, and the liquid nitrogen is gasified into nitrogen before entering the annulus, so the gas has a better penetration effect under the pressure difference. Furthermore, since the gas has an expansion property when it migrates from the high-pressure end to the low-pressure end, the volume of nitrogen will gradually expand during the process of seeping from the upper annulus to the lower wellbore, and the nitrogen with expanded volume can gradually loosen the sand plug close to the lower wellbore from far to near, and push it to the far end of the lower wellbore, thereby loosening and spreading all the sand plugs between the coiled tubing and the annulus, and even sweeping most of the sand particles to the lower wellbore far from the drilling tool position, eliminating the sand plugs to complete the unblocking. While pumping liquid nitrogen, liquid is continuously pumped into the coiled tubing to balance the pressure difference between the inside and outside of the coiled tubing and avoid crushing the coiled tubing.

[0016] The present invention provides a simple, efficient and economical method for releasing stuck coiled tubing, which can solve the problem of pipe sticking caused by sand or debris in sand flushing and drilling and grinding operations of horizontal well coiled tubing, and can effectively solve the problems in the prior art of low success rate of conventional suspension, circulation and active release treatment, and great difficulty, long time consumption and high cost in core fishing release treatment.

[0017] 2. In the present invention, before pumping sand flushing and drilling liquid into the coiled tube, the coiled tube is pressed down to make it in a compressed state rather than a stretched state (the wall thickness becomes thinner and the strength decreases in the stretched state), which can effectively avoid the coiled tube from being crushed and deformed.

[0018] 3. The present invention is provided with a mechanism for stopping the pump due to overpressure, which fully considers the existing strength of the coiled tubing and the casing pressure limit, making the unblocking process safer.

[0019] 4. The present invention maintains the pressure value at a stable value during the liquid nitrogen pumping process, and can increase the nitrogen pressure in the annulus above the sand plug as much as possible under the condition of casing pressure limitation, thereby increasing the seepage flow as much as possible and improving the jamming removal effect.

[0020] 5. The jam-releasing system of the present invention comprises a liquid nitrogen pumping device and a sand flushing and drilling and grinding liquid pumping device, which can realize the pumping of liquid nitrogen into the annulus between the coiled tubing and the casing, and the pumping of sand flushing and drilling and grinding liquid into the coiled tubing at the same time, which can solve the drill stuck accident caused by sand or debris in the sand flushing and drilling and grinding operations of the coiled tubing in the horizontal well.

[0021] 6. In the present invention, through the design of the third connecting pipe, the third stopcock and the fourth stopcock, liquid nitrogen can be pumped into the coiled tubing, and sand flushing and drilling liquid can be pumped into the annulus between the coiled tubing and the casing. It can be achieved that liquid nitrogen can be pumped into the coiled tubing and the annulus between the coiled tubing and the casing at the same time, or sand flushing and drilling liquid can be pumped into the coiled tubing and the annulus between the coiled tubing and the casing at the same time. The jamming release process can be selectively used according to actual conditions.

[0022] 7. The sand flushing, drilling and grinding liquid can be collected and recycled through the setting of the second return valve, the blowdown throttling manifold and the sand settling tank.

[0023] 8. The second connecting pipe is also provided with a filter, which is mainly used to filter the circulating sand flushing and drilling fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 It is a structural schematic diagram of the card release system in the present invention; Figure 2 It is a schematic diagram of the continuous pipe sand (debris) stuck in the drilling wellbore in the present invention; Markings in the figure: 1. Liquid nitrogen source, 2. First connecting pipe, 3. First return valve, 4. Continuous pipe, 5. Liquid nitrogen pump truck, 6. First plug valve, 7. Sand flushing and drilling liquid storage tank, 8. Second connecting pipe, 9. Pump truck, 10. Second plug valve, 11. Third connecting pipe, 12. Third plug valve, 13. Fourth plug valve, 14. Filter, 15. Second return valve, 16. Blowout throttling manifold, 17. Sand settling tank, 18. Annulus pressure, 19. Sand plug, 20. Wellbore pressure. DETAILED DESCRIPTION

[0025] Example 1 As a basic embodiment of the present invention, the present invention includes a method for releasing a stuck coiled tubing in a horizontal well, comprising the following steps: Step S 1 . When the wellhead is lost and the drill is stuck, increase the displacement of the positive circulation coiled tubing 4 to release the sticking of the upper and lower movable coiled tubing 4. If the sticking cannot be released, go to step S 2 .

[0026] Step S 2 . Pump liquid nitrogen into the annulus between coiled tubing 4 and casing, and pump sand drilling and grinding liquid into coiled tubing 4 at the same time until the unstuck operation is completed. In this process, if the liquid nitrogen pumping is overpressured, stop the pump, and continue to pump sand drilling and grinding liquid into coiled tubing 4 until the load tonnage of coiled tubing 4 increases or the pressure difference between oil and casing decreases. Then continue to pump liquid nitrogen into the annulus, and gradually reduce the pumping displacement of coiled tubing 4 until the suspended weight of coiled tubing 4 is basically normal. Then appropriately increase the displacement of coiled tubing 4 and move coiled tubing 4 up and down until the unstuck operation is completed.

[0027] Example 2 As a preferred embodiment of the present invention, the present invention includes a method for releasing a stuck coiled tubing in a horizontal well, comprising the following steps: Step S 1. When the wellhead is lost and the drill is stuck, increase the displacement of the positive circulation coiled tubing 4 to release the sticking of the upper and lower movable coiled tubing 4. If the sticking cannot be released, go to step S 2 .

[0028] Step S 2 . Considering the existing strength of the coiled tubing 4 and the casing pressure limit, an overpressure protection value is set, which is lower than the casing pressure limit. Liquid nitrogen is pumped into the annulus between the coiled tubing 4 and the casing, and sand flushing and drilling liquid is pumped into the coiled tubing 4 at the same time until the unblocking operation is completed. Before pumping sand flushing and drilling liquid into the coiled tubing 4, the coiled tubing 4 is pressed down to make it in a compressed state, rather than a stretched state, to prevent the coiled tubing 4 from being crushed and deformed.

[0029] During the process of pumping liquid nitrogen and sand drilling and milling liquid, if the liquid nitrogen pumping overpressure exceeds the preset overpressure protection value, the pump is stopped and the sand drilling and milling liquid is continued to be pumped into the coiled tubing 4. Pay close attention to the changes in oil and casing pressure and the load of the coiled tubing 4. If the tonnage of the coiled tubing 4 load increases or the oil and casing pressure difference decreases, it means that the debris (fracturing sand or drilling and milling debris) that caused the drill to get stuck has been loosened. Continue to pump liquid nitrogen into the annulus, and at the same time, gradually reduce the pumping displacement of the coiled tubing 4 until the suspended weight of the coiled tubing 4 is basically normal. Then appropriately increase the displacement of the coiled tubing 4 and move the coiled tubing 4 up and down until the unblocking operation is completed.

[0030] Example 3 As another preferred embodiment of the present invention, the present invention includes a horizontal well coiled tubing stuck release system, including a liquid nitrogen pumping device and a sand flushing drilling and milling liquid pumping device. The liquid nitrogen pumping device is used to pump liquid nitrogen into the annulus between the coiled tubing 4 and the casing, and at the same time, the sand flushing drilling and milling liquid pumping device is used to pump sand flushing drilling and milling liquid into the coiled tubing 4.

[0031] Specifically, the liquid nitrogen pumping equipment includes a liquid nitrogen source 1, a first connecting pipe 2 and a first return valve 3 connected in sequence, and the first return valve 3 is connected to the annulus of the continuous pipe 4 and the casing. The first connecting pipe 2 is also provided with a liquid nitrogen pump truck 5 and a first plug valve 6. The sand washing and drilling and milling liquid pumping equipment includes a sand washing and drilling and milling liquid storage tank 7 and a second connecting pipe 8 connected in sequence, the other end of the second connecting pipe 8 is connected to the continuous pipe 4, and the second connecting pipe 8 is also provided with a pump truck 9 and a second plug valve 10.

[0032] Use this system to unlock the card. The specific unlocking process is as follows: Open the first return valve 3, the first plug valve 6 and the second plug valve 10. Start the liquid nitrogen pump truck 5 and the pump truck 9 at the same time, and set the overpressure protection value. If the casing pressure limit is 55MPa, the overpressure protection value can be set to 54MPa at most. After the equipment is in stable operation, pump sand flushing and drilling liquid into the coiled tubing 4 through the second plug valve 10. At the same time, pump liquid nitrogen into the annulus between the coiled tubing 4 and the casing through the first plug valve 6 and the first return valve 3. Continue to pump liquid nitrogen until the pump stops due to overpressure. Close the first return valve 3 and continue to pump the coiled tubing 4 at the set displacement. During this process, pay close attention to the changes in oil and casing pressure and the changes in the load of the coiled tubing 4. If the oil and casing pressure difference increases, the pumping displacement of the coiled tubing 4 can be appropriately increased. When the suspended weight of the coiled tubing 4 rises and the oil and casing pressure difference decreases, it means that the debris (fracture sand or drilling debris) that causes the drill to get stuck has been loosened, and the coiled tubing 4 continues to be pumped. The displacement of the coiled tubing 4 is increased. At the same time, the coiled tubing 4 is moved up and down and short-distance tripping is performed until the drilling tool is dragged out of the predicted stuck well section, thus completing the unblocking operation.

[0033] Example 4 As the best embodiment of the present invention, the present invention includes a horizontal well coiled tubing stuck release system, referring to the attached specification Figure 1 , including liquid nitrogen pumping equipment and sandblasting, drilling and milling liquid pumping equipment. The liquid nitrogen pumping equipment includes a liquid nitrogen source 1, a first connecting pipe 2 and a first return valve 3 connected in sequence, and the first return valve 3 and a continuous pipe 4 are connected to the annulus of the casing. A liquid nitrogen pump truck 5 and a first stopcock 6 are also provided on the first connecting pipe 2. The liquid nitrogen source 1 is a liquid nitrogen tank truck. The sandblasting, drilling and milling liquid pumping equipment includes a sandblasting, drilling and milling liquid storage tank 7 and a second connecting pipe 8 connected in sequence, the other end of the second connecting pipe 8 is connected to the continuous pipe 4, and a pump truck 9 and a second stopcock 10 are also provided on the second connecting pipe 8.

[0034] Furthermore, it also includes a third connecting pipe 11, on which a third plug valve 12 is also provided, and on which a fourth plug valve 13 is also provided. One end of the third connecting pipe 11 is connected to the first connecting pipe 2 between the first plug valve 6 and the first return valve 3, and the other end is connected to the second connecting pipe 8 between the fourth plug valve 13 and the second plug valve 10.

[0035] Furthermore, in order to realize the recycling of the sand flushing and drilling liquid, it can also include a second return valve 15, a blowdown throttling manifold 16 and a sand settling tank 17 which are connected in sequence. The second return valve 15 and the coiled pipe 4 are connected to the annulus of the casing; the other end of the sand settling tank 17 is connected to the sand flushing and drilling liquid storage tank 7 through a fourth connecting pipe, and a pump body can be provided on the fourth connecting pipe.

[0036] Furthermore, in order to filter the circulating sand flushing and drilling fluid, a filter 14 is further provided on the second connecting pipe 8 .

[0037] The above system is used to complete the unblocking of the horizontal well coiled tubing. The specific unblocking method is as follows: Step S 1 . When the wellhead is lost and the drill is stuck, increase the displacement of the positive circulation coiled tubing 4 to release the sticking of the upper and lower movable coiled tubing 4. If the sticking cannot be released, go to step S 2 .

[0038] Step S 2 . Pump liquid nitrogen into the annulus between the coiled tubing 4 and the casing, and at the same time pump sand flushing and drilling liquid into the coiled tubing 4 until the jamming operation is completed. Specifically, the following steps are included: Step S 21 . Press down the coiled tubing 4 to the hanging weight of -8t, close the third plug valve 12, and open the first flowback valve 3, the first plug valve 6, the second plug valve 10 and the fourth plug valve 13.

[0039] Step S 22 . Start the pump truck 9 and the liquid nitrogen pump truck 5 at the same time, and set the overpressure protection value, which is lower than the casing pressure limit. If the casing pressure limit is 55MPa, the overpressure protection value can be set to 54MPa at most. After the operation state is stable, the sand flushing and drilling liquid is pumped in by the coiled tube 4 through the second plug valve 10 and the fourth plug valve 13. The displacement is determined according to the pipe diameter. Generally, the displacement of 2″ coiled tube 4 is 100L / min, 2 3 / 8 The coiled tube 4 has a displacement of 150 L / min. At the same time, liquid nitrogen is pumped into the casing annulus through the first plug valve 6 and the first flowback valve 3. Generally, the liquid nitrogen displacement is 150-200 L / min. Liquid nitrogen is continuously pumped in until the pump stops due to overpressure.

[0040] Step S 23 . Close the first return valve 3 and continue to pump the coiled tubing 4 at the set displacement. During this process, pay close attention to the changes in oil and casing pressure and the changes in the load of the coiled tubing 4. If the oil and casing pressure difference increases, the pumping displacement of the coiled tubing 4 can be appropriately increased.

[0041] Step S 24 . When the hanging weight of coiled tubing 4 increases and the differential pressure between oil and casing decreases, it indicates that the debris (fracture sand or drilling debris) that caused the drill to get stuck has been loosened, and the pumping of coiled tubing 4 can be continued. If the normal hanging weight of coiled tubing 4 is 8t, when the hanging weight is restored to ≥6t, it is considered that the hanging weight of coiled tubing 4 has basically returned to normal.

[0042] Step S 25 . Increase the displacement of coiled tube 4, generally 2″ coiled tube 4 is increased to 600L / min, 2 3 / 8The displacement of coiled tubing 4 is 750L / min. At the same time, the coiled tubing 4 is moved up and down and short-distance tripping is performed until the drilling tool is pulled out of the predicted stuck well section, completing the unblocking operation.

[0043] In the above card unlocking method, refer to the instruction manual. Figure 2 During the sand flushing or drilling process, if sand (debris) jams the drill string, and there is no response when the pipe string is lifted or lowered, that is, it is often called a complete jam, the sand plug 19 and the coiled tubing 4 separate the wellbore into two parts: the upper casing annulus and the lower wellbore.

[0044] During the continuous tubing 4 sand flushing or drilling and grinding operation, the wellbore pressure 20 is often low, generally lower than 10MPa.

[0045] Assuming the permeability of the sand plug 19 is k, and the final annular pressure 18 after the annular space is pumped with liquid nitrogen is P1, then according to the Darcy seepage formula: In the above formula, the parameters are: P1-liquid nitrogen pressure in the annulus above the sand plug 19; P2-wellbore pressure below sand plug 19; A-annulus cross-sectional area; K-permeability coefficient of liquid nitrogen or sand drilling and grinding liquid; u--dynamic viscosity of liquid nitrogen or sandblasting drilling and grinding liquid; L- length of sand plug 19 in wellbore.

[0046] In the method of unblocking by pumping liquid nitrogen into the annulus, except for P1, all the parameters of the above Darcy formula are relatively constant. In order to ensure the seepage rate Q of nitrogen or sand drilling and grinding liquid, the value of P1 should be increased as much as possible under the condition of casing pressure limitation. Therefore, in the actual unblocking operation, if the casing pressure limit is 55MPa, liquid nitrogen can be pumped into the annulus until the pressure value gradually tends to a stable value. The stable value is a stable and unchanging value when the pressure tends to a later stage of pumping, and the stable value is related to the sand plug. In this embodiment, the stable value can be 54MPa. When the pressure value of the annulus nitrogen decreases by more than 5MPa, liquid nitrogen can continue to be pumped into the annulus to maintain P1 at 54MPa.

[0047] Liquid nitrogen is gasified into nitrogen before entering the annulus. Once the nitrogen in the annulus passes through the sand plug and enters the lower wellbore, according to the ideal gas state equation pV=nRT, under wellbore conditions, the amount of nitrogen n, the gas constant R and the thermodynamic temperature T of the wellbore can be considered unchanged, and the following formula can be obtained: P1×V1=P2×V2 In the above formula, the parameters are: P1-nitrogen pressure in the upper annulus; V1-nitrogen volume in the upper annulus; P2 - Nitrogen pressure in the lower wellbore; V2 - Nitrogen volume in the lower wellbore; As can be seen from the above formula, since P1 > P2, then V1 < V2. That is to say, when gas migrates from the high - pressure end to the low - pressure end, it has an expansion property. Therefore, during the process of nitrogen seeping from the upper annulus to the lower wellbore, the volume will gradually expand. The expanded nitrogen can gradually push the sand plug 19 near the lower wellbore from far to near, and push it to the distal end of the lower wellbore, thereby pushing all the sand plugs between the coiled tubing and the annulus loose and spreading them out, and even sweeping most of the sand grains to the lower wellbore beyond the drill string position to eliminate the sand plug and complete the pipe sticking release.

[0048] Example 5 As another preferred embodiment of the present invention, the present invention includes a method for releasing a coiled tubing stuck in a horizontal well. This well is a horizontal oil well with an artificial bottom hole of 4427 m, a build - up point of 560 m, an entry window point of 2424 m, a horizontal section length of 2087 m, and a casing completion. The outer diameter of the casing is 139.7 mm and the inner diameter is 124.26 mm. The coiled tubing 4 is used for bottom - hole - sealed drag - type fracturing to transform 56 segments. After fracturing, a 2.375 - inch coiled tubing 4 is used to enter the well for sand washing. The surface choke manifold controls the back - pressure between 2.2 - 4.4 MPa through a 16 - mm choke nozzle. During this period, the coiled tubing is pulled up and back 6 times, and the cumulative sand production is about 8 m 3 ; When sand washing reaches 3672 m and is pulled back to 2627 m, the wellhead loses return and the wellhead pressure drops from 3.9 MPa to 0. When pulling up, it gets stuck, and the maximum pulling force is 18.4 t (the normal hanging weight during pulling back is 16 t). Open the side - wing channel on the other side of the Christmas tree, and adjust the choke manifold to the direct - discharge channel (without a choke nozzle). The pumping displacement of the coiled tubing 4 is 700 - 900 L / min, and the wellhead still loses return.

[0049] Stuck - pipe release stage 1: Stop pulling up the coiled tubing 4, increase the displacement and try to move the coiled tubing 4 to release the stuck pipe. Specifically, increase the pumping displacement. The return port intermittently discharges liquid, and the return displacement is 20 - 500 L / min. Try to pull up and push down the drill string. The maximum pulling force is 18.4 t, and the pushing force is - 8 t. The stuck - pipe release by moving fails.

[0050] Stuck - pipe release stage 2: Pump liquid nitrogen into the coiled tubing 4 to supplement energy to the formation, observe the change of the return port, and move the coiled tubing 4 to release the stuck pipe as appropriate. Specifically, press down the coiled tubing 4 to - 8 t, and pump 19.1 m of liquid nitrogen into the pipe 3 , After 6 hours, the return port discharges a small amount of liquid. After about 1 - 2 minutes, the liquid discharge stops. About 6 hours after the liquid - nitrogen pump stops pumping, a stream of liquid about 10 - 20 L returns every 3 - 4 minutes. After nearly 1 hour, the liquid discharge stops; Pump 38.4 m of liquid nitrogen into the pipe again 3After the coiled tube was moved in the range of maximum down pressure of -8t to maximum up pressure of 15t for 4.2 hours, an intermittent outflow of liquid and gas occurred at the return outlet, which lasted for nearly 15 minutes, but the jam was not successfully released.

[0051] Stage 3 of unblocking: Pump liquid nitrogen from the annulus, and pump liquid into coiled tubing 4 at the same time, observe the changes in pressure and load, and try to unblock. First, pump liquid through coiled tubing 4 at a displacement of 700L / min, and then pump liquid nitrogen from the annulus to 48MPa and stop the pump. The casing pressure drops rapidly to about 18.0MPa, and the hanging weight gradually returns to near normal tonnage. Adjust the hanging weight to 3t, and after rapid pressure relief at the wellhead, move coiled tubing 4 to 2533m. During this process, the return fluid volume gradually increases from 10L / min to 400-500L / min, and the liquid output is continuous. Ensure that the displacement of coiled tubing 4 remains unchanged, pay close attention to the changes in hanging weight, and if there is a jam, lift the movable coiled tubing 4 shortly, and if the hanging weight is normal, lift it continuously to successfully pull out coiled tubing 4.

[0052] In summary, after reading the present invention document, ordinary technicians in this field can make various other corresponding transformation schemes based on the technical scheme and technical concept of the present invention without creative mental labor, which all fall within the scope of protection of the present invention.

Claims

1. A method for releasing a stuck coiled tubing in a horizontal well, characterized by: The following steps are involved: Step S1. When the wellhead is lost and the drill is stuck, the displacement of the positive circulation coiled tubing (4) is increased to release the upper and lower movable coiled tubing (4). If the pipe cannot be released, proceed to step S2; Step S2. Liquid nitrogen is pumped into the annulus between the coiled tubing (4) and the casing, and sand flushing and drilling liquid is pumped into the coiled tubing (4) at the same time, until the jam-releasing operation is completed; during this process, if the liquid nitrogen pumping exceeds the pressure, the pump is stopped, and the sand flushing and drilling liquid is continuously pumped into the coiled tubing (4) until the load tonnage of the coiled tubing (4) increases or the pressure difference between the oil and casing decreases, and then the liquid nitrogen is continuously pumped into the annulus, and at the same time, the pumping displacement of the coiled tubing (4) is gradually reduced until the suspended weight of the coiled tubing (4) is basically normal; then the displacement of the coiled tubing (4) is increased and the coiled tubing (4) is moved up and down until the jam-releasing operation is completed.

2. A method for releasing a stuck coiled tubing in a horizontal well according to claim 1, characterized in that: Before pumping sand flushing and drilling liquid into the coiled tube (4), the coiled tube (4) is pressed down to put it in a compressed state.

3. A method for releasing a stuck coiled tubing in a horizontal well according to claim 1, characterized in that: The overpressure specifically refers to exceeding a preset overpressure protection value, and the overpressure protection value is lower than the casing limit pressure.

4. A method for releasing a stuck coiled tubing in a horizontal well according to claim 1, characterized in that: During the liquid nitrogen pumping process, liquid nitrogen is pumped into the annulus until the pressure value gradually tends to a stable value; if the pressure value of the liquid nitrogen in the annulus decreases by more than 5MPa, liquid nitrogen is continued to be pumped into the annulus to maintain the pressure value at a stable value.

5. A method for releasing a stuck coiled tubing in a horizontal well according to claim 1, characterized in that: During the unblocking operation, if the pressure difference between the oil and the casing increases, the pumping rate of the coiled tubing (4) is increased.

6. A horizontal well coiled tubing jam release system, characterized by: It comprises liquid nitrogen pumping equipment and sand flushing drilling and grinding liquid pumping equipment, wherein the liquid nitrogen pumping equipment is used to pump liquid nitrogen into the annulus between the coiled tubing (4) and the casing, and the sand flushing drilling and grinding liquid pumping equipment is used to pump sand flushing drilling and grinding liquid into the coiled tubing (4) while pumping liquid nitrogen.

7. A horizontal well coiled tubing jam release system according to claim 6, characterized in that: The liquid nitrogen pumping equipment comprises a liquid nitrogen source (1), a first connecting pipe (2) and a first return valve (3) which are connected in sequence, the other end of the first return valve (3) being connected to the coiled pipe (4) and the annulus of the casing; the first connecting pipe (2) is also provided with a liquid nitrogen pump truck (5) and a first stopcock (6); the sand washing and drilling and milling liquid pumping equipment comprises a sand washing and drilling and milling liquid storage tank (7) and a second connecting pipe (8) which are connected in sequence, the other end of the second connecting pipe (8) being connected to the coiled pipe (4), the second connecting pipe (8) is also provided with a pump truck (9) and a second stopcock (10).

8. A horizontal well coiled tubing jam release system according to claim 7, characterized in that: The third connecting pipe (11) further comprises a third plug valve (12) on the third connecting pipe (11), and a fourth plug valve (13) on the second connecting pipe (8); one end of the third connecting pipe (11) is connected to the first connecting pipe (2) between the first plug valve (6) and the first return valve (3), and the other end is connected to the second connecting pipe (8) between the fourth plug valve (13) and the second plug valve (10).

9. A horizontal well coiled tubing jam release system according to claim 8, characterized in that: The second connecting pipe (8) is also provided with a filter (14).

10. A horizontal well coiled tubing jam release system according to claim 9, characterized in that: It also includes a second return valve (15), a blowdown throttling manifold (16), and a sand settling tank (17) which are connected in sequence; the second return valve (15) and the continuous pipe (4) are connected to the annulus of the casing; the other end of the sand settling tank (17) is connected to the sand flushing and drilling liquid storage tank (7) through a fourth connecting pipe.

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