Pressure-controlled drilling and grinding method for oil horizontal well with super-long horizontal section

Abstract

The invention discloses a pressure-controlled drilling and grinding method for an oil horizontal well with an ultra-long horizontal section. The pressure-controlled drilling and grinding method comprises the following steps that firstly, construction design is compiled, and a well mouth is prepared, installed and subjected to pressure testing; 2, optimization design of the combined pipe column is carried out; thirdly, a pump truck, well repairing equipment and a ground pressure control process are installed; 4, the pipe column is combined, and an underground drilling and grinding tool is assembled; and 5, pressure-controlled drilling and grinding construction is carried out. According to the pressure control drilling and grinding method for the horizontal well of the horizontal section above 4000 m, while composite drilling is achieved through the adjustable weighting type power faucet and the underground power motor, the combined pipe column and efficient resistance reducing liquid are matched, the technologies of ground throttling pressure control and the like are combined, the drift diameter of a shaft is recovered after drilling and grinding, meanwhile, reservoir damage is reduced, and the drilling and grinding efficiency is improved. Efficient development of a low-permeability oil-gas field is achieved, and the single-well yield is increased.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a pressure-controlled drilling and grinding method for an ultra-long horizontal section oil well. Background Art

[0002] In the process of oil exploration and development, hydraulic fracturing is an effective reservoir transformation technology. The Ordos Basin is rich in oil and gas resources, mainly composed of low permeability, ultra-low permeability, and tight oil and gas reservoirs. With the development of exploration and development technology, there are more and more horizontal wells with ultra-long horizontal sections (horizontal sections are more than 4,000 meters long) in Changqing Oilfield. The reservoir transformation process is mainly based on bridge-shot combined staged fracturing. After fracturing, there are undissolved bridge plugs and proppant returned from the formation in the wellbore, which block the formation fluid production channel and seriously affect the single well production capacity. It is necessary to carry out wellbore cleaning operations after fracturing to restore the production channel. Conventional repair equipment and tools cannot meet the pipe string depth requirements of horizontal wells with ultra-long horizontal sections (horizontal sections longer than 4000m), and metal drag reducers need to be continuously circulated during post-pressure drilling and grinding of bridge plugs and sand flushing. The continuously returned formation fluid contaminates the metal drag reducers, causing them to lose their drag reduction function. The drilling and grinding fluid needs to be replaced continuously, which consumes a large amount of fluid. Frequent well pressure suppression after overflow during wellbore cleaning will cause reservoir pollution and affect the transformation effect. Therefore, it is urgent to carry out research on horizontal well pressure-controlled drilling and grinding process technology. At the same time, in order to make up for the problem of limited operation length of the combined pipe string to extend the horizontal section, it is necessary to match the ground weighting equipment to form the pressure-controlled drilling and grinding operation capability of horizontal wells with horizontal sections of more than 4000m, and provide technical support for the transformation of ultra-long horizontal sections of oil horizontal wells.

[0003] The invention's ultra-long horizontal section oil well pressure-controlled drilling and grinding technology uses an adjustable heavy-duty power faucet and a downhole power motor to achieve compound drilling, and is equipped with a combined pipe column, high-efficiency resistance-reducing liquid, and combined with ground throttling and pressure control technologies to form a pressure-controlled drilling and grinding process technology for horizontal wells in a horizontal section of more than 4,000 meters. It can effectively solve on-site production problems, increase production speed and efficiency, and reduce construction risks. It has obvious advantages such as fast construction speed, closed wellhead, low cost, and deep and long pipe column limit. The drilling and grinding implementation method can save time and labor, is safe, environmentally friendly, and controllable, and increases single well production, which is conducive to the further implementation of oil and gas development in Changqing Oilfield. Summary of the invention

[0004] In view of the problems in the related technology, the purpose of the present invention is to solve the problems of self-locking of the tubing during the drilling and grinding of ultra-long horizontal oil wells, which cannot realize wellbore cleaning and restore the wellbore diameter, and the reservoir contamination by the well-killing fluid, according to the actual needs of the drilling and grinding operation site of oil and gas field development. A pressure-controlled drilling and grinding method for ultra-long horizontal oil wells is provided. While an adjustable heavy-duty power faucet and a downhole power motor are used to achieve composite drilling, a combination of tubing, high-efficiency resistance-reducing liquid, and ground throttling and pressure control technologies are used to form a pressure-controlled drilling and grinding method for horizontal wells with a horizontal section of more than 4000m. The wellbore diameter is restored after drilling and grinding, and reservoir damage is reduced, thereby achieving efficient development of low-permeability oil and gas fields and increasing single well production.

[0005] The objective of the present invention is achieved through the following technical solutions: A pressure-controlled drilling and grinding method for an ultra-long horizontal section oil well comprises the following steps: Step 1: Installation of wellhead equipment, pump truck, workover equipment, ground pressure control process, combined pipe string and downhole drilling and grinding tools; Step 2: After installation, assemble the drilling and grinding tools into the well according to the design. During the process of drilling the combined pipe string, adjust the sealing pressure of the rotary well sealer in time according to the wellhead pressure. After drilling and exploring the sand surface, lift a pipe string, start the pump for positive circulation, continue to adjust the sealing pressure of the rotary well sealer, and slowly lower the combined pipe string for drilling and grinding. The liquid is pumped into the pipe, returned along the annulus, and returned to the ground through the wellhead four-way. The ground is throttled and pressure controlled by the high-pressure chip catcher and the double-branch throttle manifold. During the drilling and grinding process, the drilling speed is strictly controlled to clean the drill cuttings out of the wellbore to prevent the drill from getting stuck. After the downhole drilling and grinding tool enters the horizontal section for a certain distance, the combined pipe string will self-lock. After self-locking, start the adjustable heavy-duty power faucet; repeat the above operations to complete all bridge plug drilling and grinding to ensure that the wellbore is clean and unobstructed. After drilling and grinding to the artificial bottom of the well, continue to circulate 2 to 3 times the wellbore volume to flush the return fluid from the wellhead without impurities, and then start drilling and complete the well.

[0006] Preferably, in step one, before the wellhead device is installed, a unit with design qualifications prepares a construction design and submits it to relevant departments for review. After the review is passed, the wellhead device is connected from top to bottom to a rotary well plug, a double-gate hydraulic blowout preventer, a wellhead four-way valve and a large-diameter flat valve. After the wellhead device is installed, a sealing test is performed by closing the large-diameter flat valve and injecting water and pressurizing it with a pump truck.

[0007] Preferably, in step one, an optimized design of the combined tubing string is required before installation. The wellbore is established and the wellbore trajectory is simulated using tubing string mechanics analysis software based on the measured well inclination data of a single well and the casing data of the oil layer of the well, and the insertability of the operating tubing string is analyzed in the established simulated wellbore.

[0008] Preferably, the well oil layer casing data includes deflection depth and azimuth.

[0009] Preferably, in step one, the placement of the pump truck, well repair equipment and ground pressure control process is selected according to the construction site conditions and safety operation requirements, and the connections are strictly carried out in accordance with the construction standards.

[0010] Preferably, the surface pressure control process includes a high-pressure chip catcher, a double-branch throttling manifold and a sand settling tank or a vibrating screen connected in sequence.

[0011] Preferably, in step one, a downhole drilling template tool is selected according to design requirements, the combined pipe string is connected to the downhole drilling template tool, and the downhole drilling and grinding tool is connected to a double-flap check valve, a safety release, a screw motor and a grinding shoe in sequence from top to bottom.

[0012] Preferably, check the appearance, inspection report and certificate of the downhole drilling template tool on site, and record the length, outer diameter and inner diameter of the double-flap check valve, safety release, screw motor and grinding shoe in detail; test the sealing of the double-flap check valve by filling water and whether the screw motor can rotate on the ground. Only after passing the test can you enter the well.

[0013] Preferably, in step 2, when adjusting the sealing pressure of the rotary well plug, the sealing pressure is continued to be increased when there is liquid leakage at the wellhead, with no liquid leakage at the wellhead as the standard, otherwise the sealing pressure is continued to be increased until there is no leakage at the rotary well plug, ensuring that the wellhead meets the requirements of the pressure-controlled drilling and grinding operation.

[0014] Preferably, in the step 2, when the sealing pressure continues to increase when the wellhead liquid leaks, the blowout discharge volume is controlled by adjusting the size of the throttling oil nozzle of the double-branch throttling manifold, and the blowout discharge volume is controlled to be not less than 600-800 L / min; when the combined pipe string is slowly lowered for drilling and grinding, the injection discharge volume is 500-700 L / min, the drilling pressure loaded on the ground after drilling and encountering the bridge plug does not exceed 1-3t, the ground pump pressure during drilling and grinding is greater than the no-load pump pressure by 3.0-5.0MPa, and the construction pressure is not more than 28.0MPa.

[0015] Preferably, in the step 2, when the ground is throttling and controlling the pressure through the high-pressure chip catcher and the double-branch throttling manifold, the return displacement is controlled to be not less than 600-800 L / min, and the drilling speed is strictly controlled during the drilling and grinding process to ensure that the drilling pressure loaded on the ground is not more than 1-3t, and the ground pump pressure is 3.0-5.0MPa greater than the no-load pump pressure during drilling and grinding. A fixed-point cycle is performed every 200-400m of penetration to clean the drill cuttings out of the wellbore in time to prevent the drill from getting stuck. After the downhole drilling template tool enters the horizontal section for a certain distance, the combined pipe string will self-lock, and after self-locking, the adjustable aggravated power faucet will be started. The adjustable aggravated power faucet is connected to the pipe string through the drill pipe buckle, and the combined pipe string is rotated by the adjustable aggravated power faucet to improve the state of the pipe string in the well and extend the depth of the pipe string. The heavy-duty power swivel provides a torque no greater than the minimum torsional strength of the drilling and grinding pipe string in the well; at the same time, the metal drag reducer is replaced in conjunction with the positive circulation to reduce the friction between the combined pipe string and the casing, so as to further extend the depth of the pipe string; in the case that the combined pipe string still self-locks under the action of the rotary running and the metal drag reducer, the ground weight can be increased by 1 to 5 tons through the counterweight block to further extend the limit of the pipe string. Repeat the above operations to complete all the bridge plug drilling and grinding, ensure that the wellbore is clean and unobstructed, and continue to circulate 2 to 3 times the wellbore volume after drilling and grinding to the artificial bottom position, flush until the return fluid from the wellhead is free of impurities, and then start drilling and complete the well.

[0016] The beneficial effects of this technical solution are as follows: 1. The present invention provides a pressure-controlled drilling and grinding method for ultra-long horizontal section oil horizontal wells. The well repair equipment, wellhead equipment, combined tubing and downhole drilling and grinding tools in the pressure-controlled drilling and grinding method for ultra-long horizontal section oil horizontal wells are mature and reliable, and integrated innovation is carried out to provide a process technology for the effective development of oil and gas reservoirs under ultra-long horizontal section wellbore conditions.

[0017] 2. The present invention provides a pressure-controlled drilling and grinding method for ultra-long horizontal section oil wells. Through the matching adjustable heavy-duty power faucet and ground pressure-controlled drilling and grinding device, it can meet the needs of wellbore cleaning of oil horizontal wells within a water-to-vertical ratio of 2.5 and a wellhead pressure within 10.0 MPa, and meets the technical requirements of oil exploration and development in the Changqing area.

[0018] 3. The present invention provides a pressure-controlled drilling and grinding method for ultra-long horizontal section oil wells, downhole drilling and grinding tools and tubing, which have a simple and reasonable structure and can effectively solve technical problems such as self-locking of the tubing, inability to thoroughly clean the wellbore, and blowout overflow. The drilling and grinding implementation method is an efficient wellbore cleaning method.

[0019] 4. The invention provides a pressure-controlled drilling and grinding method for ultra-long horizontal oil wells, which achieves complete sealing of the wellhead by rotating the well sealer to prevent the working liquid from falling to the ground, thus meeting the relevant requirements for environmental protection during oil exploration and development, and the environmental risks are controllable.

[0020] 5. The present invention provides a pressure-controlled drilling and grinding method for ultra-long horizontal oil wells. The return displacement can be adjusted and controlled in real time by adjusting the size of the throttling oil nozzle of the double-branch throttling manifold. While reducing reservoir damage, the formation energy is maximized, and the annular sand carrying effect is improved. While improving the drilling and grinding efficiency, the risk of engineering accidents such as drill sticking is reduced, which significantly reduces the accident rate of on-site construction and saves costs for underground construction units. It is an essential device for achieving efficient development of oil and gas fields and has good promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the installation of the wellhead device, the combined pipe string and the downhole drilling and grinding tool in the present invention; Figure 2 It is a schematic diagram of the structure of the wellhead device and the pipe string in the present invention; Figure 3 It is a structural schematic diagram of the adjustable heavy-duty power faucet in the invention; Among them: 1. Rotary well plugger, 2. Double-gate hydraulic blowout preventer, 3. Wellhead spool, 4. Large-diameter flat valve, 5. Combined pipe string, 6. Double-disc check valve, 7. Safety release, 8. Screw motor, 9. Grinding shoe, 10. High-pressure chip catcher, 11. Double-branch throttling manifold, 12. Sand settling tank or vibrating screen, 13. Power swivel, 14. Counterweight. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0023] It should be noted that when a component is referred to as being "mounted on", "fixed on" or "disposed on" another component, it may be directly on the other component or there may be a central component at the same time. When a component is referred to as being "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time.

[0024] It should also be noted that the directional terms such as left, right, up, and down in the embodiments of the present invention are merely relative concepts or are based on the normal use status of the product and should not be considered as restrictive.

[0025] like Figure 1-Figure 3 As shown, a pressure-controlled drilling and grinding method for an ultra-long horizontal section oil well comprises the following steps: Step 1: Installation of wellhead equipment, pump truck, well repair equipment, ground pressure control process, combined pipe string 5 and downhole drilling and grinding tools; Step 2: After the installation is completed, the drilling and grinding tools are assembled and put into the well according to the design. During the drilling of the combined pipe string 5, the sealing pressure of the rotary well plug 1 is adjusted in time according to the wellhead pressure. After drilling and exploring the sand surface, a pipe string is lifted, the pump is turned on for positive circulation, the sealing pressure of the rotary well plug 1 is continued to be adjusted, and the combined pipe string 5 is slowly lowered for drilling and grinding; the liquid is pumped into the pipe, returned along the annulus, and returned to the ground through the wellhead spool 3. The ground is throttled and pressure controlled through the high-pressure chip catcher 10 and the double-branch throttling manifold 11. During the drilling and grinding process, the drilling speed is strictly controlled to clean the drill cuttings out of the wellbore to prevent the drill from getting stuck. After the downhole drilling and grinding tool enters the horizontal section for a certain distance, the combined pipe string 5 will self-lock. After self-locking, the adjustable heavy-duty power faucet 13 is started; the above operation is repeated to complete all the bridge plug drilling and grinding to ensure that the wellbore is clean and unobstructed. After drilling and grinding to the artificial bottom of the well, continue to circulate 2 to 3 times the wellbore volume to flush the return fluid from the wellhead without impurities, and then start drilling and complete the well.

[0026] Preparation of construction design, wellhead preparation, installation and pressure testing Among them, in the step one, before the wellhead device is installed, a unit with design qualifications prepares a construction design and submits it to the relevant departments for review. After the review is passed, the wellhead device is connected from top to bottom with a rotary well plug 1, a double-gate hydraulic blowout preventer 2, a wellhead four-way valve 3 and a large-diameter flat valve 4. After the wellhead device is installed, the large-diameter flat valve 4 is closed and the pump truck is used to inject water and pressurize it for sealing.

[0027] Combined pipe string 5 optimization design Among them, in the step 1, the combined pipe string 5 needs to be optimized before installation. It is necessary to use the pipe string mechanics analysis software to establish the wellbore and simulate the wellbore trajectory based on the measured well deviation data of the single well and the casing data of the well oil layer, and analyze the running performance of the working pipe string in the established simulated wellbore. 1 / 2" casing completed oil horizontal well, the combined pipe string 5 for the pressure controlled drilling and grinding operation includes a 3 1 / 2″ small coupling drill pipe, diameter 2 7 / 8″ drill pipe and 2 dia. 3 / 8″ drill rod.

[0028] The well oil layer casing data include inclined depth and azimuth.

[0029] Installation of pump trucks, well repair equipment and ground pressure control procedures Among them, in the step one, the placement of the pump truck, well repair equipment and ground pressure control process is selected according to the construction site conditions and safety operation requirements, and the connections are strictly in accordance with the construction standards.

[0030] The ground pressure control process includes a high-pressure chip collector 10, a double-branch throttling manifold 11 and a sand settling tank or a vibrating screen 12 which are connected in sequence.

[0031] Assembly of combined pipe string and downhole drilling and grinding tools Among them, in the step one, a downhole drilling template tool is selected according to the design requirements, the combined pipe string 5 is connected to the downhole drilling template tool, and the downhole drilling and grinding tool is connected to the double-flap check valve 6, the safety release 7, the screw motor 8 and the grinding shoe 9 from top to bottom in sequence.

[0032] Among them, check the appearance, inspection report and certificate of qualification of the downhole drilling template tools on site, and record in detail the length, outer diameter and inner diameter of the double-flap check valve 6, safety release hand 7, screw motor 8 and grinding shoe 9 (through the length, outer diameter and inner diameter of the double-flap check valve 6, safety release hand 7, screw motor 8 and grinding shoe 9 on the vernier caliper or tape measure side); test the sealing of the double-flap check valve 6 by water filling test and whether the screw motor 8 can rotate on the ground. Only after passing the test can the well be entered.

[0033] Controlled pressure drilling and grinding construction Among them, in step 2, when adjusting the sealing pressure of the rotary well plug 1, the sealing pressure is continued to be increased when liquid leaks from the wellhead, with no liquid leakage from the wellhead as the standard. Otherwise, the sealing pressure is continued to be increased until the rotary well plug 1 has no leakage, ensuring that the wellhead meets the requirements of pressure-controlled drilling and grinding operations.

[0034] Among them, in the step 2, when the sealing pressure continues to increase when the wellhead liquid leaks, the size of the throttling oil nozzle of the double-branch throttling manifold 11 is adjusted to control the blowout discharge volume, and the blowout discharge volume is controlled to be not less than 600-800 L / min; when the combined pipe string 5 is slowly lowered for drilling and grinding, the injection discharge volume is 500-700 L / min, the drilling pressure loaded on the ground after drilling and encountering the bridge plug does not exceed 1-3t, the ground pump pressure during drilling and grinding is greater than the no-load pump pressure by 3.0-5.0MPa, and the construction pressure is not more than 28.0MPa.

[0035] Among them, in the step 2, when the ground is throttling and controlling the pressure through the high-pressure chip catcher 10 and the double-branch throttling manifold 11, the return displacement is controlled to be not less than 600-800 L / min, and the drilling speed is strictly controlled during the drilling and grinding process to ensure that the drilling pressure loaded on the ground is not more than 1-3t, and the ground pump pressure during drilling and grinding is 3.0-5.0MPa greater than the no-load pump pressure. A fixed-point cycle is performed every 200-400m of penetration to clean the drill cuttings out of the wellbore in time to prevent the drill from getting stuck. After the downhole drilling template tool enters the horizontal section for a certain distance, the combined pipe string 5 will self-lock, and after self-locking, the adjustable aggravated power faucet 13 will be started. The adjustable aggravated power faucet 13 is connected to the pipe string through the drill pipe buckle. The combined pipe string 5 is rotated by the adjustable aggravated power faucet 13 to improve the state of the pipe string in the well and extend the depth of the pipe string. The heavy-duty power swivel 13 provides a torque not greater than the minimum torsional strength of the drilling and grinding pipe string in the well; at the same time, the metal drag reducer is replaced in conjunction with the positive circulation to reduce the friction between the combined pipe string 5 and the casing, so as to further extend the depth of the pipe string; in the case that the combined pipe string still self-locks under the action of the rotation and the metal drag reducer, the counterweight block 14 can be used to increase the ground weight by 1 to 5 tons to further extend the limit of the pipe string. The above operations are repeated to complete all the bridge plug drilling and grinding to ensure that the wellbore is clean and unobstructed. After drilling and grinding to the artificial bottom of the well, continue to circulate 2 to 3 times the wellbore volume to flush the return fluid from the wellhead without impurities, and then start drilling and complete the well.

[0036] The beneficial effects of this technical solution are as follows: 1. The present invention provides a pressure-controlled drilling and grinding method for an ultra-long horizontal section oil well. The well repair equipment, wellhead device, combined tubing string 5 and downhole drilling and grinding tools in the pressure-controlled drilling and grinding method for an ultra-long horizontal section oil well are mature and reliable, and integrated innovation is carried out to provide a process technology for the effective development of oil and gas reservoirs under ultra-long horizontal section wellbore conditions.

[0037] 2. The present invention provides a pressure-controlled drilling and grinding method for oil horizontal wells with ultra-long horizontal sections. Through the matching adjustable heavy-duty power faucet 13 and ground pressure-controlled drilling and grinding device, it meets the needs of wellbore cleaning of oil horizontal wells within a water-to-vertical ratio of 2.5 and a wellhead pressure within 10.0 MPa, and meets the technical requirements of oil exploration and development in the Changqing area.

[0038] 3. The present invention provides a pressure-controlled drilling and grinding method for ultra-long horizontal section oil wells, downhole drilling and grinding tools and tubing, which have a simple and reasonable structure and can effectively solve technical problems such as self-locking of the tubing, inability to thoroughly clean the wellbore, and blowout overflow. The drilling and grinding implementation method is an efficient wellbore cleaning method.

[0039] 4. The invention provides a pressure-controlled drilling and grinding method for an ultra-long horizontal section oil well, which achieves complete sealing of the wellhead by rotating the well sealer 1 to prevent the working liquid from falling to the ground, thus meeting the relevant requirements for environmental protection during oil exploration and development, and the environmental risks are controllable.

[0040] 5. The present invention provides a method for controlled pressure drilling and grinding of ultra-long horizontal oil wells. The return displacement can be adjusted and controlled in real time by adjusting the size of the throttling oil nozzle of the double-branch throttling manifold 11. While reducing reservoir damage, the formation energy is maximized, and the annular space sand carrying effect is improved. While improving the drilling and grinding efficiency, the risk of engineering accidents such as drill sticking is reduced, which significantly reduces the accident rate of on-site construction and saves costs for underground construction units. It is an essential device for realizing the efficient development of oil and gas fields and has a good promotion prospect.

[0041] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A pressure-controlled drilling and grinding method for ultra-long horizontal section oil wells, characterized in that: The following steps are involved: Step 1: Installation of wellhead equipment, pump truck, workover equipment, ground pressure control process, combined pipe string and downhole drilling and grinding tools; Step 2: After installation, assemble the drilling and grinding tools into the well according to the design. During the process of drilling the combined pipe string, adjust the sealing pressure of the rotary well sealer in time according to the wellhead pressure. After drilling and exploring the sand surface, lift a pipe string, start the pump for positive circulation, continue to adjust the sealing pressure of the rotary well sealer, and slowly lower the combined pipe string for drilling and grinding. The liquid is pumped into the pipe, returned along the annulus, and returned to the ground through the wellhead four-way. The ground is throttled and pressure controlled by the high-pressure chip catcher and the double-branch throttle manifold. During the drilling and grinding process, the drilling speed is strictly controlled to clean the drill cuttings out of the wellbore to prevent the drill from getting stuck. After the downhole drilling and grinding tool enters the horizontal section for a certain distance, the combined pipe string will self-lock. After self-locking, start the adjustable heavy-duty power faucet; repeat the above operations to complete all bridge plug drilling and grinding to ensure that the wellbore is clean and unobstructed. After drilling and grinding to the artificial bottom of the well, continue to circulate 2 to 3 times the wellbore volume to flush the return fluid from the wellhead without impurities, and then start drilling and complete the well.

2. The controlled pressure drilling and grinding method for ultra-long horizontal section oil wells according to claim 1 is characterized by: In the step 1, before the wellhead device is installed, a unit with design qualifications prepares a construction design and submits it to the relevant departments for review. After the review is passed, the wellhead device is connected from top to bottom with a rotary well plug, a double-gate hydraulic blowout preventer, a wellhead four-way valve and a large-diameter flat valve. After the wellhead device is installed, a sealing test is performed by closing the large-diameter flat valve and injecting water into the pump truck for pressure testing.

3. The controlled pressure drilling and grinding method for ultra-long horizontal section oil wells according to claim 1, characterized in that: In the step 1, the combined tubing string needs to be optimized and designed before installation. It is necessary to establish a wellbore and simulate the wellbore trajectory using tubing string mechanics analysis software based on the measured well inclination data of a single well and the casing data of the well oil layer, and analyze the insertability of the operating tubing string in the established simulated wellbore.

4. The controlled pressure drilling and grinding method for ultra-long horizontal section oil wells according to claim 3 is characterized by: The well oil layer casing data include deflection depth and azimuth.

5. The controlled pressure drilling and grinding method for ultra-long horizontal section oil wells according to claim 1, characterized in that: In the step 1, the placement of the pump truck, well repair equipment and ground pressure control process is selected according to the construction site conditions and safety operation requirements, and the connections are strictly carried out in accordance with the construction standards.

6. The controlled pressure drilling and grinding method for ultra-long horizontal section oil wells according to claim 1, characterized in that: In the step 1, a downhole drilling jig tool is selected according to the design requirements, the combined pipe string is connected to the downhole drilling jig tool, and the downhole drilling and grinding tool is connected to a double-flap check valve, a safety release, a screw motor and a grinding shoe in sequence from top to bottom.

7. The controlled pressure drilling and grinding method for ultra-long horizontal section oil wells according to claim 1, characterized in that: Check the appearance, inspection report and certificate of the downhole drilling template tools on site, and record in detail the length, outer diameter and inner diameter of the double-flap check valve, safety release, screw motor and grinding shoe; test the water sealing of the double-flap check valve and whether the screw motor can rotate on the ground. Only after passing the test can you enter the well.

8. The controlled pressure drilling and grinding method for ultra-long horizontal section oil wells according to claim 1, characterized in that: In step 2, when adjusting the sealing pressure of the rotary well plug, continue to increase the sealing pressure when there is liquid leakage at the wellhead, with no liquid leakage at the wellhead as the standard. Otherwise, continue to increase the sealing pressure until there is no leakage at the rotary well plug, ensuring that the wellhead meets the requirements of the pressure-controlled drilling and grinding operation.

9. The controlled pressure drilling and grinding method for ultra-long horizontal section oil wells according to claim 1, characterized in that: In the step 2, when the sealing pressure continues to increase when the wellhead liquid leaks, the blowout discharge volume is controlled by adjusting the size of the throttling oil nozzle of the double-branch throttling manifold, and the blowout discharge volume is controlled to be not less than 600-800 L / min; when the combined pipe string is slowly lowered for drilling and grinding, the injection discharge volume is 500-700 L / min, the drilling pressure loaded on the ground after encountering the bridge plug does not exceed 1-3 tons, the ground pump pressure during drilling and grinding is greater than the no-load pump pressure by 3.0-5.0 MPa, and the construction pressure is not more than 28.0 MPa.

10. The controlled pressure drilling and grinding method for ultra-long horizontal section oil wells according to claim 1, characterized in that: In the step 2, when the ground is throttling and controlling the pressure through the high-pressure chip catcher and the double-branch throttling manifold, the return displacement is controlled to be not less than 600-800 L / min. When the drilling speed is strictly controlled during the drilling and grinding process, it is ensured that the drilling pressure loaded on the ground is not more than 1-3t. The ground pump pressure during drilling and grinding is 3.0-5.0MPa greater than the no-load pump pressure. A fixed-point cycle is performed every 200-400m of penetration to clean the drill cuttings out of the wellbore in time to prevent the drill from getting stuck. After the downhole drilling template tool enters the horizontal section for a certain distance, the combined pipe string will self-lock. After self-locking, the adjustable heavy-duty power faucet is started. The adjustable heavy-duty power faucet is connected to the pipe string through the drill pipe buckle. The combined pipe string is rotated by the adjustable heavy-duty power faucet to improve the state of the pipe string in the well and extend the depth of the pipe string. The heavy-duty power swivel provides a torque no greater than the minimum torsional strength of the drilling and grinding pipe string in the well; at the same time, the metal drag reducer is replaced in conjunction with the positive circulation to reduce the friction between the combined pipe string and the casing, so as to further extend the depth of the pipe string; in the case that the combined pipe string still self-locks under the action of the rotary running and the metal drag reducer, the ground weight can be increased by 1 to 5 tons through the counterweight block to further extend the limit of the pipe string. Repeat the above operations to complete all the bridge plug drilling and grinding, ensure that the wellbore is clean and unobstructed, and continue to circulate 2 to 3 times the wellbore volume after drilling and grinding to the artificial bottom position, flush until the return fluid from the wellhead is free of impurities, and then start drilling and complete the well.

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