Nitrogen foam downhole gas-liquid separation drilling and grinding tool string and using method

Abstract

The invention discloses a nitrogen foam downhole gas-liquid separation drilling and grinding tool string and a using method, and relates to the technical field of oil and gas resource development, the nitrogen foam downhole gas-liquid separation drilling and grinding tool string comprises a coiled tubing connector, a double-clack check valve, a safety release, a gas-liquid separation valve, a hydraulic oscillator, a screw motor and a grinding shoe which are sequentially connected through threads, and one end of the coiled tubing connector is fixedly connected with the coiled tubing. The using method of the nitrogen foam downhole gas-liquid separation drilling and grinding tool string comprises the steps that the tool string is prepared; performing tension and pressure tests on the tool string on the ground; testing the shunting state of the gas-liquid separation valve and the working state of a screw motor; the tool string drills downwards; and well washing, drilling and grinding and back-dragging cleaning are repeatedly carried out. In the drilling and grinding operation, nitrogen foam working fluid can be pumped and injected at the same time, the annular flow velocity can be increased while the motor is protected, the sand washing or drilling and grinding efficiency is improved, the drilling and grinding and sand carrying functions are achieved at the same time, the problems that low-pressure oil and gas well circulation cannot be established, and the sand washing and drilling and grinding operation efficiency is low are solved, and stratum pollution is reduced.

Description

Technical Field

[0001] The patent of this invention belongs to the technical field of oil and gas resource development, and specifically relates to a nitrogen foam downhole gas-liquid separation drilling and grinding tool string and a method of use. Background Art

[0002] The Ordos Basin is a typical low-permeability, low-pressure oil and gas field. The pressure coefficient of the oil and gas layer is generally low, with a gas reservoir of 0.85-0.9 and an oil reservoir of 0.7-0.8. The pressure coefficient of old wells is even lower after exploitation. Wells in the Changqing area that use the bridge-shot continuous staged fracturing process usually use 2in or 2.375in continuous tubing to carry conventional drilling and grinding tool strings for operation. The circulating working fluid is usually clean water or return fluid with a certain concentration of thickener added, and the liquid density is usually greater than 1. In addition, most old wells currently use water-based well-killing fluid for well washing, sand flushing, drilling and grinding operations. Since the formation pressure coefficient is less than 1, sand flushing, well washing, drilling and grinding will cause liquid loss, and some wells cannot establish circulation, which brings great difficulty to carrying sand during sand flushing operations. It is impossible to carry wellbore debris to the ground, and sand often gets stuck in the pipe column during drilling and grinding. At the same time, this type of drilling and grinding tool string currently has a single wellbore cleaning method for low-pressure leakage wells. During the operation, it is necessary to repeatedly run drilling and grinding, flushing, strong magnetic fishing and other tool strings to complete different operation tasks, resulting in a large amount of well killing fluid leakage and low efficiency. On the other hand, due to the large amount of well killing fluid intrusion, the drainage cycle is prolonged, which seriously affects the recovery of oil and gas well production capacity.

[0003] The Chinese invention patent document with announcement number CN115680528A and publication date of February 3, 2023, proposes a horizontal well coiled tubing nitrogen foam sand flushing device and its construction method. The horizontal well coiled tubing nitrogen foam sand flushing device includes: a foam generating device, a coiled tubing device, a wellhead device and a ground backflow device. After the coiled tubing device is connected to the foam generating device, it is lowered to the bottom of the well through the production valve of the wellhead device, and the ground backflow device is connected to the casing valve of the wellhead device. The above-mentioned horizontal well coiled tubing nitrogen foam sand flushing construction method includes the following steps: S1, construction preparation; S2, equipment performance test; S3, sand surface exploration; S4, sand flushing operation; S5, well washing; S6, oil pipe lifting. The invention can solve the problem that the horizontal well sand flushing cycle is difficult to establish and the sand flushing is not thorough. It has the characteristics of clear operation steps, strong operability, and clear parameter values.

[0004] However, the above technical solutions, on the one hand, cannot carry the wellbore debris to the ground, and the efficiency of sand flushing or drilling is not ideal. On the other hand, during the operation, a large amount of working fluid invades the formation, and the drainage cycle is prolonged, which seriously affects the recovery of oil and gas well production capacity. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a nitrogen foam downhole gas-liquid separation drilling and grinding tool string and a use method. The use of this tool solves the technical problems of motor stalling, torque loss and damage caused by gas passing through the screw motor. During the drilling and grinding operation, nitrogen foam working fluid is pumped at the same time, which can increase the annular space flow rate while protecting the motor, improve sand flushing or drilling and grinding efficiency, and reduce formation pollution.

[0006] The present invention is achieved by adopting the following technical solutions: A nitrogen foam downhole gas-liquid separation drilling and grinding tool string comprises a coiled tubing connector, a double-flap check valve, a safety release, a gas-liquid separation valve, a hydraulic oscillator, a screw motor and a grinding shoe. The coiled tubing connector, the double-flap check valve, the safety release, the gas-liquid separation valve, the hydraulic oscillator, the screw motor and the grinding shoe are connected in sequence through threads. The upper joint of the coiled tubing connector is fixedly connected to the coiled tubing through slips and rivets, and the lower joint is connected to the double-flap check valve.

[0007] The underground gas-liquid separation valve is provided with a turbine fan blade, and a liquid hole and a plug are provided on the shell.

[0008] The coiled tubing is lowered into the set position by the deadweight of the coiled tubing and the downward thrust exerted by the coiled tubing injection head for well washing and drilling operations. The double-flap check valve has a hydraulically opened one-way valve disc inside. As a downhole tool, it can prevent the bottom hole fluid from flowing up the string inside the tube, protecting the downhole drilling and grinding tools and preventing blowouts in the well control. The main function of the safety release in the tool string is to release the next tool string by throwing a ball when the drilling and grinding or wellbore cleaning tool string is stuck, ensuring that the coiled tubing can be pulled out of the wellhead to prevent engineering complications and accidents. The downhole gas-liquid separation valve tool has a turbofan blade inside, and the shell has a liquid hole and a plug. When the mixed fluid is pumped through the tool, the blade will separate part or all of the nitrogen gas into the annulus through the rotating fluid, protecting the screw motor. The hydraulic oscillator produces longitudinal reciprocating motion in the wellbore under the action of hydraulic pressure, The temporary static friction of the tool string at the bottom of the well is converted into dynamic friction, which can increase the drilling pressure on the drill bit in long horizontal wells or operations with complex wellbore trajectories, and can effectively reduce the drilling tool drag pressure caused by the wellbore trajectory; the function of the screw motor is to pass the separated foam working fluid in several sealed chambers formed by the rotor and stator with a spiral surface, so that the rotor rotates and drives the grinding shoe to rotate to clean the debris in the wellbore.

[0009] A method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string comprises the following steps: Step 1: Prepare the tool string; Step 2: Perform tension and pressure tests on the tool string on the ground; Step 3, testing the flow separation of the gas-liquid separation valve and the working state of the screw motor; Step 4: Drilling the tool string; Step 5: well washing, drilling and grinding; Step 6, back-pull cleaning; the back-pull cleaning means that after drilling and grinding a number of bridge plugs or flushing a certain length of sand footage, the coiled tubing is slowly pulled back to clean the debris in the wellbore, and short-lifted and lowered several times at the bridge plug position for full circulation; after pulling back to the wellbore window point position, several times the volume of working fluid is circulated in the wellbore to ensure that the wellbore is clean; Step 7: Repeat steps 5 and 6 until the wellbore cleaning operation is completed.

[0010] The preparation tool string refers to connecting the upper joint of the coiled tubing connector to the coiled tubing through slips and rivets, and the other tool accessories are connected together in sequence through threads.

[0011] The tension and pressure test on the tool string on the ground refers to controlling the gas-liquid separation ratio by adjusting the number of plugs on the gas-liquid separator tool according to the formation equivalent density and the required gas-liquid density.

[0012] The test of the flow diversion of the gas-liquid separation valve and the working state of the screw motor refers to first pumping nitrogen foam working fluid on the ground, and stopping the pump after confirming that the working state is normal and the gas-liquid separation is normal.

[0013] The tool string drilling refers to lowering the connected tool string into the coiled tubing by relying on the deadweight of the coiled tubing and the downward thrust provided by the coiled tubing injection head to explore the position of the wellbore bridge plug or debris.

[0014] The well washing and drilling and grinding mentioned above refer to lifting the drill tool to a certain length and performing positive circulation well washing or drilling and grinding according to the construction design requirements; after the nitrogen gas and foam working fluid returned from the outlet are normal, the coiled tubing is continuously lowered at the speed required by the design.

[0015] The drilling tool is lifted up by a certain length, that is, the drilling tool is lifted up by 1-3m.

[0016] The number of bridge plugs drilled and ground or the length of sand flushing footage is 3-5 bridge plugs drilled and ground or the sand flushing footage is 300-500m; the number of short lifts and lowers at the bridge plug position is 3-4 short lifts and lowers at the bridge plug position; the number of times the volume of the working fluid in the wellbore is 1.5-2 times the volume of the working fluid in the wellbore.

[0017] Compared with the prior art, the advantages of the present invention are: 1. The present invention solves the technical defect that nitrogen cannot be pumped in the drilling and grinding operation, and solves the technical problem that the gas passes through the screw motor, causing the motor to stall, lose torque and be damaged. During the drilling and grinding operation, nitrogen foam working fluid can be pumped in at the same time, which can increase the annular flow rate while protecting the motor, and improve the sand flushing or drilling and grinding efficiency.

[0018] 2. By adopting the present invention, the density of the fluid can be adjusted by adjusting the proportion of nitrogen foam, so that the density of the wellbore liquid and the equivalent density of the formation can be close, thereby reducing formation pollution and reducing the impact on the recovery of oil and gas well production capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 This is a structural diagram of a nitrogen foam downhole gas-liquid separation drilling and grinding tool string.

[0020] Markings in the figure: 1. Continuous tubing connector; 2. Double-flap check valve; 3. Safety release; 4. Gas-liquid separation valve; 5. Hydraulic oscillator; 6. Screw motor; 7. Grinding shoe. DETAILED DESCRIPTION

[0021] Example 1 A nitrogen foam downhole gas-liquid separation drilling and grinding tool string comprises a coiled tubing connector 1, a double-flap check valve 2, a safety release 3, a gas-liquid separation valve 4, a hydraulic oscillator 5, a screw motor 6 and a grinding shoe 7. The coiled tubing connector 1, the double-flap check valve 2, the safety release 3, the gas-liquid separation valve 4, the hydraulic oscillator 5, the screw motor 6 and the grinding shoe 7 are connected in sequence by threads. The upper joint of the coiled tubing connector 1 is fixedly connected to the coiled tubing by slips and rivets, and the lower joint is connected to the double-flap check valve 2.

[0022] The coiled tubing is lowered into the set position by the deadweight of the coiled tubing and the downward thrust exerted by the coiled tubing injection head for well washing and drilling operations. The double-flap check valve 2 has a one-way valve disc that can be hydraulically opened inside. As a downhole tool, it can prevent the bottom hole liquid from flowing up the string inside the tube, protecting the downhole drilling and grinding tools and preventing blowouts in the well control. The main function of the safety release 3 in the tool string is to release the next tool string by throwing a ball when the drilling and grinding or wellbore cleaning tool string is stuck, ensuring that the coiled tubing can be pulled out of the wellhead to prevent engineering complications and accidents. The downhole gas-liquid separation valve 4 tool has a turbofan blade inside, and the shell has a liquid hole and a plug. When the mixed fluid is pumped through the tool, the blade will rotate the fluid. The nitrogen gas is partially or completely separated into the annulus, which plays a role in protecting the screw motor 6; the hydraulic oscillator 5 generates longitudinal reciprocating motion in the wellbore under the action of hydraulic pressure, and the temporary static friction of the tool string at the bottom of the well is converted into dynamic friction. In long horizontal wells or operations with complex wellbore trajectories, the drilling pressure on the drill bit can be increased, and the drilling tool drag pressure phenomenon caused by the wellbore trajectory can be effectively reduced; the function of the screw motor 6 is to rotate the rotor in several sealed cavities formed by the rotor and stator with a spiral surface through the separated foam working fluid, driving the grinding shoe 7 to rotate to clean the debris in the wellbore.

[0023] Example 2 Based on Example 1, a method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string includes the following steps: Step 1: Prepare the tool string; Step 2: Perform tension and pressure tests on the tool string on the ground; Step 3, testing the flow separation of the gas-liquid separation valve 4 and the working state of the screw motor 6; Step 4: Drilling the tool string; Step 5: well washing, drilling and grinding; Step 6, back-pull cleaning; the back-pull cleaning means that after drilling and grinding a number of bridge plugs or flushing a certain length of sand footage, the coiled tubing is slowly pulled back to clean the debris in the wellbore, and short-lifted and lowered several times at the bridge plug position for full circulation; after pulling back to the wellbore window point position, several times the volume of working fluid is circulated in the wellbore to ensure that the wellbore is clean; Step 7: Repeat steps 5 and 6 until the wellbore cleaning operation is completed.

[0024] This embodiment is the most basic implementation method, step 1, prepare the tool string; step 2, perform tension and pressure tests on the tool string on the ground; step 3, test the diversion of the gas-liquid separation valve 4 and the working state of the screw motor 6; step 4, drill the tool string; step 5, wash the well, drill and grind; step 6, pull back and clean; step 7, repeat steps 5 and 6 until the wellbore cleaning operation is completed. Compared with the prior art, it solves the technical defect that nitrogen cannot be pumped simultaneously during previous drilling and grinding operations, and solves the technical problem that gas passes through the screw motor 6, causing motor stalling, torque loss and damage. During the drilling and grinding operation, nitrogen foam working fluid is pumped at the same time, which can increase the annular flow rate while protecting the motor, and improve the efficiency of sand flushing or drilling and grinding.

[0025] Example 3 On the basis of Example 2, a method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string comprises the following steps: Step 1: Prepare the tool string; Step 2: Perform tension and pressure tests on the tool string on the ground; Step 3, testing the flow separation of the gas-liquid separation valve 4 and the working state of the screw motor 6; Step 4: Drilling the tool string; Step 5: well washing, drilling and grinding; Step 6, back-pull cleaning; the back-pull cleaning means that after drilling and grinding a number of bridge plugs or flushing a certain length of sand footage, the coiled tubing is slowly pulled back to clean the debris in the wellbore, and short-lifted and lowered several times at the bridge plug position for full circulation; after pulling back to the wellbore window point position, several times the volume of working fluid is circulated in the wellbore to ensure that the wellbore is clean; Step 7: Repeat steps 5 and 6 until the wellbore cleaning operation is completed.

[0026] Furthermore, the preparation tool string refers to connecting the upper joint of the coiled tubing connector 1 to the coiled tubing through slips and rivets, and the other tool accessories are sequentially connected together through threads.

[0027] Furthermore, the tension and pressure test on the tool string on the ground refers to controlling the gas-liquid separation ratio by adjusting the number of plugs on the gas-liquid separator tool according to the formation equivalent density and the required gas-liquid density.

[0028] Furthermore, the test of the flow diversion of the gas-liquid separation valve 4 and the working state of the screw motor 6 refers to first pumping nitrogen foam working fluid on the ground, and stopping the pump after confirming that the working state is normal and the gas-liquid separation is normal.

[0029] Furthermore, the tool string drilling refers to lowering the connected tool string into the coiled tubing by relying on the deadweight of the coiled tubing and the downward thrust provided by the coiled tubing injection head to explore the position of the wellbore bridge plug or debris.

[0030] Furthermore, the well washing and drilling and grinding mentioned above refer to lifting the drill bit for a certain length and performing positive circulation well washing or drilling and grinding according to the construction design requirements; after the nitrogen gas and foam working fluid returned from the outlet are normal, the continuous oil pipe is continuously lowered at the speed required by the design.

[0031] Example 4 On the basis of Example 3, a method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string comprises the following steps: Step 1: Prepare the tool string; Step 2: Perform tension and pressure tests on the tool string on the ground; Step 3, testing the flow separation of the gas-liquid separation valve 4 and the working state of the screw motor 6; Step 4: Drilling the tool string; Step 5: well washing, drilling and grinding; Step 6, back-pull cleaning; the back-pull cleaning means that after drilling and grinding a number of bridge plugs or flushing a certain length of sand footage, the coiled tubing is slowly pulled back to clean the debris in the wellbore, and short-lifted and lowered several times at the bridge plug position for full circulation; after pulling back to the wellbore window point position, several times the volume of working fluid is circulated in the wellbore to ensure that the wellbore is clean; Step 7: Repeat steps 5 and 6 until the wellbore cleaning operation is completed.

[0032] Furthermore, the preparation tool string refers to connecting the upper joint of the coiled tubing connector 1 to the coiled tubing through slips and rivets, and the other tool accessories are connected together in sequence through threads, such as the attached Figure 1 shown.

[0033] Furthermore, the tension and pressure test on the tool string on the ground refers to controlling the gas-liquid separation ratio by adjusting the number of plugs on the gas-liquid separator tool according to the formation equivalent density and the required gas-liquid density.

[0034] Furthermore, the test of the flow diversion of the gas-liquid separation valve 4 and the working state of the screw motor 6 refers to first pumping nitrogen foam working fluid on the ground, and stopping the pump after confirming that the working state is normal and the gas-liquid separation is normal.

[0035] Furthermore, the tool string drilling refers to lowering the connected tool string into the coiled tubing by relying on the deadweight of the coiled tubing and the downward thrust provided by the coiled tubing injection head to explore the position of the wellbore bridge plug or debris.

[0036] Furthermore, the well washing and drilling and grinding mentioned above refer to lifting the drill bit for a certain length and performing positive circulation well washing or drilling and grinding according to the construction design requirements; after the nitrogen gas and foam working fluid returned from the outlet are normal, the continuous oil pipe is continuously lowered at the speed required by the design.

[0037] Furthermore, the lifting of the drilling tool by a certain length is lifting the drilling tool by 1-3m.

[0038] Furthermore, the drilling and grinding of a number of bridge plugs or the sand flushing footage of a number of lengths is 3-5 bridge plugs or the sand flushing footage is 300-500m; the short lift and lowering at the bridge plug position a number of times is 3-4 short lift and lowering at the bridge plug position; the working fluid of a number of times the volume of the wellbore is 1.5-2 times the volume of the wellbore.

[0039] This embodiment is the best implementation method, which can simultaneously meet the drilling and sand carrying functions, solve the problem that low-pressure oil and gas well circulation cannot be established and the efficiency of sand flushing, drilling and grinding operations is low. At the same time, the density of the fluid can be adjusted by adjusting the proportion of nitrogen foam, so that the density of the wellbore liquid and the equivalent density of the formation can be close, thereby reducing formation pollution.

Claims

1. A nitrogen foam downhole gas-liquid separation drilling and grinding tool string, Features: The invention comprises a continuous tubing connector (1), a double-flap check valve (2), a safety release (3), a gas-liquid separation valve (4), a hydraulic oscillator (5), a screw motor (6) and a grinding shoe (7), wherein the continuous tubing connector (1), the double-flap check valve (2), the safety release (3), the gas-liquid separation valve (4), the hydraulic oscillator (5), the screw motor (6) and the grinding shoe (7) are connected in sequence by threads, and the upper joint of the continuous tubing connector (1) is fixedly connected to the continuous tubing by means of slips and rivets, and the lower joint is connected to the double-flap check valve (2).

2. A nitrogen foam downhole gas-liquid separation drilling and grinding tool string according to claim 1, Features: The downhole gas-liquid separation valve (4) is provided with a turbine fan blade, and a liquid hole and a plug are provided on the shell.

3. A method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string, Features: The following steps are involved: Step 1: Prepare the tool string; Step 2: Perform tension and pressure tests on the tool string on the ground; Step 3, testing the flow separation of the gas-liquid separation valve (4) and the working state of the screw motor (6); Step 4: Drilling the tool string; Step 5: well washing, drilling and grinding; Step 6, back-pull cleaning; the back-pull cleaning means that after drilling and grinding a number of bridge plugs or flushing a certain length of sand footage, the coiled tubing is slowly pulled back to clean the debris in the wellbore, and short-lifted and lowered several times at the bridge plug position for full circulation; after pulling back to the wellbore window point position, several times the volume of working fluid is circulated in the wellbore to ensure that the wellbore is clean; Step 7: Repeat steps 5 and 6 until the wellbore cleaning operation is completed.

4. A method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string according to claim 3, Features: The preparation tool string refers to connecting the upper joint of the coiled tubing connector (1) to the coiled tubing through slips and rivets, and the other tool accessories are connected together in sequence through threads.

5. The method for using the nitrogen foam downhole gas-liquid separation drilling and grinding tool string according to claim 3, Features: The tension and pressure test on the tool string on the ground refers to controlling the gas-liquid separation ratio by adjusting the number of plugs on the gas-liquid separator tool according to the formation equivalent density and the required gas-liquid density.

6. A method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string according to claim 3, Features: The test of the flow diversion of the gas-liquid separation valve (4) and the working state of the screw motor (6) is to first pump nitrogen foam working fluid on the ground, and then stop the pump after confirming that the working state is normal and the gas-liquid separation is normal.

7. The method for using the nitrogen foam downhole gas-liquid separation drilling and grinding tool string according to claim 3, Features: The tool string drilling refers to lowering the connected tool string into the coiled tubing by relying on the deadweight of the coiled tubing and the downward thrust provided by the coiled tubing injection head to explore the position of the wellbore bridge plug or debris.

8. The method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string according to claim 3, Features: The well washing and drilling and grinding mentioned above refer to lifting the drill tool to a certain length and performing positive circulation well washing or drilling and grinding according to the construction design requirements; after the nitrogen gas and foam working fluid returned from the outlet are normal, the coiled tubing is continuously lowered at the speed required by the design.

9. A method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string according to claim 8, Features: The drilling tool is lifted up by a certain length, that is, the drilling tool is lifted up by 1-3m.

10. The method for using a nitrogen foam downhole gas-liquid separation drilling and grinding tool string according to claim 3, Features: The number of bridge plugs drilled and ground or the length of sand flushing footage is 3-5 bridge plugs drilled and ground or the sand flushing footage is 300-500m; the number of short lifts and lowers at the bridge plug position is 3-4 short lifts and lowers at the bridge plug position; the number of times the volume of the working fluid in the wellbore is 1.5-2 times the volume of the working fluid in the wellbore.

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