A method for drilling multi-branch wells for marine natural gas hydrates using recoverable directional drilling tools, fishing equipment, and processes.

Abstract

This invention discloses a recoverable directional drilling tool, retrieval tool, and process for multi-branch well drilling of marine natural gas hydrates, relating to the field of marine natural gas hydrate drilling and production. It includes a directional drilling tool body and a retrieval sub. The directional drilling tool body has a guide surface, and a release sub is located in the middle of the body. A drill string through-hole is formed within the body, and a blind plug is connected to one side. The retrieval sub has an internal thread on one side, and on the other side, from the outside in, are a retrieval guide, a positioning key guide, and a positioning key sleeve arranged sequentially. This invention eliminates the need for gyro positioning to determine the directional drilling tool's orientation during adjustment; the directional drilling tool can be directly deployed to lock the tool and accurately adjust the orientation of the directional drilling face. This results in high adjustment efficiency, makes the directional drilling tool recoverable, reduces the difficulty of subsequent construction operations, and the retrieval process is simple and reliable, with stronger adaptability to complex deep-water downhole environments.

Description

Technical Field

[0001] This invention relates to the field of drilling and production of marine natural gas hydrates, specifically to a recoverable directional drilling tool and retrieval equipment and process for multi-branch well drilling of marine natural gas hydrates. Background Technology

[0002] Multi-branch wells, also known as multi-bottom wells, are created by drilling multiple branch wells from a single main well using specialized drilling tools. Based on the difficulty of drilling and completing multi-branch wells, the oil and gas industry currently classifies them into seven levels: TAML1 to TAML6 and TAML6S. Among them, TAML6S is the most complex level of multi-branch well drilling and completion. It uses special tools to separate the branch wells after the drilling and completion tools are inserted into the well, and finally isolates and seals each other for independent production, enabling a single well to simultaneously exploit multiple pressure systems.

[0003] Currently, in the field of conventional oil and gas multi-branch well drilling, directional drilling tools have evolved from the initial fixed-at-the-bottom design for single-use directional drilling to reusable tools. However, the success rate and efficiency of directional drilling tool recovery remain low, and failure to recover the tool can lead to wellbore abandonment. On the other hand, directional drilling tools used in diagenetic formations such as oil and gas or coalbed methane often employ bottom cementing to create bottom supports, using the jaw plates and wellbore support to restrict the axial and circumferential movement of the directional drilling tool. This is extremely difficult to achieve in marine hydrate reservoirs. The reason is that marine natural gas hydrates are shallow, the formation is not cemented, and the jaw plates on the directional drilling tool cannot form good contact with the wellbore. The bottom cement plug easily sinks, making it impossible to fix the directional drilling tool in the axial and circumferential directions. Finally, the traditional directional drilling tool's directional surface is a spatial inclined plane. During drilling, the tool face of the directional drilling tool is unstable and easily deviates along the direction of the directional surface, reducing the efficiency of window drilling and threatening the safety of the main wellbore.

[0004] Chinese patent ZL200510135261.5 describes a recoverable directional drilling tool and its retrieval method. The directional drilling tool consists of an upper body and a lower body, mainly composed of a guide ramp, a retrieval groove, a guide key, and a retrieval cup. This directional drilling tool can be used for open-hole and casing sidetracking in diagenetic formations, and can improve the positioning accuracy and retrieval success rate to a certain extent. However, this directional drilling tool cannot be used for sidetracking multi-branch wells in offshore natural gas hydrate formations, as the wellbore or bottom hole cannot provide sufficient support, and the branch wells cannot be successfully sidetracked.

[0005] Chinese patent application CN110939387 A describes a directional drilling chuck. This chuck consists of a guide sleeve, a setting assembly, and a drive assembly, eliminating the need for a motor, hydraulic cylinder, or other power source. This simplifies the chuck's structure and reduces assembly difficulty and maintenance costs. However, this chuck can only be used for open-hole sidetracking in diagenetic formations and is not suitable for drilling multi-branch wells in offshore natural gas hydrate areas.

[0006] In 2020, my country achieved the world's first successful trial production of offshore natural gas hydrate using horizontal well technology. The daily gas production of a single well was more than five times that of the first round of offshore natural gas hydrate trial production, demonstrating that extending the contact length between the wellbore and the reservoir can significantly increase gas production. Therefore, multi-branch well drilling and completion technology will be a key development direction for the industrialization of hydrates. Due to the formation characteristics of offshore natural gas hydrates, conventional multi-branch well drilling tools used in diagenetic formations are difficult to use directly. Therefore, based on the patent "Multi-branch Well Branching Mechanism and Well Construction Method for Offshore Natural Gas Hydrate Drilling (Application No.: 2021106271350)," a directional drilling tool suitable for multi-branch well drilling and completion of offshore natural gas hydrates was designed.

[0007] To improve the single-well productivity of marine natural gas hydrates, reduce development costs, and increase development efficiency, this invention provides a recoverable adjustable directional guide suitable for the development of multi-branch wells of marine natural gas hydrate TAML6S class. This invention improves the efficiency and accuracy of adjusting the directional guide's orientation during branch well drilling, and the directional guide will not move upwards during branch well drilling, remaining in a relatively stable axial state. Recovery is safe and reliable, thus improving the drilling efficiency of multi-branch wells. Summary of the Invention

[0008] Based on this, the purpose of this invention is to provide a recoverable directional guide and retrieval tool and process for drilling multi-branch wells of marine natural gas hydrates, so as to solve the technical problems of low efficiency and accuracy of adjusting the directional guide position during existing branch well drilling.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a retrievable directional drilling tool for multi-branch wells of natural gas hydrates, comprising a directional drilling tool body, a guide slope provided within the directional drilling tool body, a drop-out short section provided in the middle of the directional drilling tool body, a drill bit through hole provided through the directional drilling tool body, and a blind plug connected to one side of the directional drilling tool body.

[0010] By adopting the above technical solution, it is not necessary to use a gyroscope to determine the orientation of the inclinometer when adjusting its position. The inclinometer can be locked directly by using a retrieval tool, thus accurately adjusting the orientation of the inclinometer to create the inclined plane, resulting in high adjustment efficiency.

[0011] The present invention is further configured such that the outer surface of the inclined device body is provided with multiple sets of straightening strips.

[0012] By adopting the above technical solution, the directional drilling rig can maintain relative axial stability during the branch well drilling process, ensuring the safety of the wellbore and drill string during the branch well drilling process.

[0013] The present invention is further configured such that the outer wall of the release section is provided with multiple sets of pins.

[0014] The above technical solution is used in conjunction with the recycling of short sections.

[0015] A retrieval tool for multi-branch well drilling of natural gas hydrates using a retrievable directional guide includes a retrieval sub. One side of the retrieval sub is provided with an internal thread, and the other side is provided with a retrieval guide, a positioning key guide, and a positioning key sleeve in sequence from the outside to the inside.

[0016] By adopting the above technical solutions, the directional diverter is made retrievable, reducing the difficulty of subsequent construction operations. The simple and reliable recovery process can shorten the construction time. The entire process of lowering, adjusting the orientation, and recovering the directional diverter is carried out by mechanical operation without electrical components, making it more adaptable to the complex environment of deep water wells.

[0017] A process for using reusable directional drilling tools in multi-branch well drilling for natural gas hydrates includes the following steps:

[0018] Step 1: Connect the slant and feed it into the tool string.

[0019] Connect the lifting sub, the variable thread connector, and the recovery sub. Lift the lifting clamp to the wellhead, remove the lifting sub, and connect a 5-7 / 8″ drill pipe.

[0020] Step 2: Connect the slant gear

[0021] Hoist the directional box containing the directional device to the wellhead, lower the retrieval sub, connect and lock the directional device;

[0022] Step 3: Insert the directional drilling rig into the casing of the branch well.

[0023] Connect the 5-7 / 8″ drill pipe and lower the directional drill.

[0024] Step 4: Adjust the orientation of the swashplate, then release the swashplate.

[0025] The directional tool is sent to a depth of 10m from the designed well depth. The drilling rig heave compensation is activated, the directional tool is adjusted, and after it is lowered into place, the drill string is reversed 10°, the tool is pulled up and sent in, and the directional tool is released.

[0026] Step 5: Connect the branch wellbore drilling tools

[0027] Connecting the drill string assembly for branch well drilling: 8-1 / 2″ drill bit, 6-3 / 4″ bent housing screw, variable thread connector, 5-1 / 2″ non-magnetic weighted drill pipe, MWD, 5-1 / 2″ non-magnetic weighted drill pipe, variable thread connector, 5-1 / 2″ drill pipe, variable thread connector, 5-7 / 8″ drill pipe to the drilling platform;

[0028] Step Six: Drilling

[0029] When the drill string reaches 20m below the sea surface, the pump is started, and the screw pressure drop and MWD measurement parameters are tested at different displacements. If the results are normal, the drill string continues to be lowered. Tests are conducted every 500m, and the test data is recorded. When the drill string is 10m away from the directional drilling rig, the heave compensation device is activated, and the pump is started at a low displacement. Based on the drill string azimuth obtained from the MWD measurement, the drill string azimuth is adjusted to be consistent with the azimuth of the drill string through hole. The drill string is lowered slowly. After the drill string passes the directional drilling rig, it is lowered slowly according to the length of the branch well casing in the multi-branch well structure. After bottoming out, the drill string is raised by 2m, and the pump is started at a normal displacement. The float shoes and cementing tools are drilled and ground. After the drill string drills out of the casing shoe, normal directional drilling is carried out to complete the branch well drilling operation.

[0030] Step 7: Pulling out the drill bit

[0031] After drilling the branch well to the designed depth, a thick plug is applied and circulated for two weeks. Then, normal drilling fluid is used to reverse the drilling and pull the drill string to the branch well casing. Next, the pipeline is switched to replace the seawater, the mud pump is turned up to increase the displacement, and the directional pump is repeatedly flushed. The ROV observes that the fluid returning from the subsea wellhead is clean. Then, reverse the drilling and pull the drill string back to the bottom of the branch well. After pulling out the drill string through hole, the drill string is circulated at a fixed point with a large displacement until the ROV observes that the fluid returning from the subsea wellhead is clean. Then, reverse the drilling and pull the drill string back to the bottom of the branch well. The sealing drilling fluid is introduced, the drill string is pulled out, and the branch well completion casing is assembled and run in. The casing hanger is set inside the branch well casing, and the first branch well is completed.

[0032] Step 8: Completion of remaining branch wells

[0033] Repeat steps six and seven above to complete the remaining branch wells;

[0034] Step 9: Feed the downslope into the tool string and adjust the downslope's orientation.

[0035] Connect the lifting sub, adapter, and retrieval sub. Lift the jack to the wellhead. Disconnect the lifting sub. Assemble the directional drilling tool string: 5-7 / 8″ drill pipe, adapter, stabilizer, adapter, 5-7 / 8″ drill pipe, adapter, and retrieval sub. Mark a vertical line on the bottom 5-7 / 8″ drill pipe of the directional drilling tool string. Lower the retrieval sub to a position 10m from the directional drilling tool. Activate the heave compensation device and record the drill string weight at this point. Unlock the drill string top drive to allow free rotation. Slowly lower the retrieval sub, observing the weight and drill string bottom depth from the subsea wellhead using the ROV. When the drill string is lowered to the bottom, the directional tool pin should be guided into the positioning key in the recovery section. Rotate the drill string forward 10°, then lift the drill string and observe the suspended weight. If the drill string suspended weight increases and the directional tool wet weight increases, it indicates that the directional tool and the recovery tool are successfully locked. Lift the directional tool and insert it into the drill string to disengage the blind plug from contact with the multi-branch well branch mechanism. Rotate the drill string clockwise or counterclockwise 120° to align the drill string through hole with the second branch well casing of the multi-branch well branch mechanism. Lower the directional tool to the multi-branch well branch mechanism. At the same time, check the drill string suspended weight to determine if the directional tool is in place by checking if the directional tool wet weight decreases. Unlock the top drive, reverse the drill string 10°, lift the drill string and insert the tool, and release the directional tool.

[0036] Step 10: Run the production test string to prepare for mining.

[0037] In summary, the present invention has the following main beneficial effects:

[0038] This invention eliminates the need for gyroscope positioning to determine the orientation of the inclinometer when adjusting its position. Instead, the inclinometer can be locked directly by lowering the retrieval tool, allowing for accurate adjustment of the inclinometer's orientation and resulting in high adjustment efficiency.

[0039] This invention ensures the safety of the wellbore and drill string by maintaining relative axial stability of the directional tool during branch well drilling.

[0040] This invention creates an inclined surface that is spatially eccentric conical surface using an inclination device. The tool face of the inclination drilling tool is stable, the branch wellbore can be quickly separated from the main wellbore, the branch wellbore has high window-opening side-drilling efficiency, and it is beneficial to the safety of the main wellbore.

[0041] This invention reduces the difficulty of later construction work by having a recyclable function;

[0042] This invention features a simple and reliable recycling process that can shorten construction time.

[0043] This invention utilizes a mechanical operation for the entire process of lowering, adjusting the orientation, and retrieving the directional device, without any electrical components, making it more adaptable to complex environments in deep water wells. Attached Figure Description

[0044] Figure 1This is a front perspective view of the oblique actuator body of the present invention;

[0045] Figure 2 This is a rear perspective view of the oblique actuator body of the present invention;

[0046] Figure 3 This is a perspective view of the drop-off section of the present invention;

[0047] Figure 4 This is a perspective view of the recyclable short section of the present invention;

[0048] Figure 5 This is a side internal view of the recyclable section of the present invention.

[0049] In the diagram: 1. Incliner body; 2. Blind plug; 3. Straightening bar; 4. Drill bit through hole; 5. Guide slope; 6. Retrieval sub; 7. Release sub; 8. Pin; 9. Retrieval guide; 10. Locating key guide; 11. Locating sleeve; 12. Internal thread. Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0051] The embodiments of the present invention will now be described.

[0052] A type of multi-branch well drilling for natural gas hydrates uses a retrievable directional drilling tool, such as Figure 1-3 As shown, the directional jack body 1 is provided with a guide surface 5, and a release sub 7 is provided in the middle of the directional jack body 1. A drill string through hole 4 is provided through the directional jack body 1. A blind plug 2 is connected to one side of the directional jack body 1. Multiple sets of centering bars 3 are provided on the outer surface of the directional jack body 1. During the drilling of the branch well, the directional jack axis can maintain relative stability, ensuring the safety of the wellbore and drill string during the drilling of the branch well. Multiple sets of pins 8 are provided on the outer wall of the release sub 7 for cooperation with the recovery sub 7.

[0053] A method for drilling multi-branch wells for natural gas hydrates uses a retrievable directional drilling tool for retrieval, such as... Figure 4-5 As shown, one side of the recovery section 6 is provided with an internal thread 12, and the other side is provided with a recovery guide 9, a positioning key guide 10, and a positioning key sleeve 11 in sequence from the outside to the inside, so that the directional device has a recovery function, reducing the difficulty of later construction operations. The recovery process is simple and reliable, which can shorten the construction time. The entire process of the directional device being lowered, adjusted in orientation, and recovered is carried out by mechanical operation without electrical components, making it more adaptable to the complex environment of deep water wells.

[0054] A process for using reusable directional drilling tools in multi-branch well drilling for natural gas hydrates includes the following steps:

[0055] Step 1: Connect the slant and feed it into the tool string.

[0056] Connect the lifting sub, the variable thread connector, and the recovery sub. Lift the lifting clamp to the wellhead, remove the lifting sub, and connect a 5-7 / 8″ drill pipe.

[0057] Step 2: Connect the slant gear

[0058] Hoist the directional box containing the directional device to the wellhead, lower the retrieval sub, connect and lock the directional device;

[0059] Step 3: Insert the directional drilling rig into the casing of the branch well.

[0060] Connect the 5-7 / 8″ drill pipe and lower the directional drill.

[0061] Step 4: Adjust the orientation of the swashplate, then release the swashplate.

[0062] The directional tool is sent to a depth of 10m from the designed well depth. The drilling rig heave compensation is activated, the directional tool is adjusted, and after it is lowered into place, the drill string is reversed 10°, the tool is pulled up and sent in, and the directional tool is released.

[0063] Step 5: Connect the branch wellbore drilling tools

[0064] Connecting the drill string assembly for branch well drilling: 8-1 / 2″ drill bit, 6-3 / 4″ bent housing screw, variable thread connector, 5-1 / 2″ non-magnetic weighted drill pipe, MWD, 5-1 / 2″ non-magnetic weighted drill pipe, variable thread connector, 5-1 / 2″ drill pipe, variable thread connector, 5-7 / 8″ drill pipe to the drilling platform;

[0065] Step Six: Drilling

[0066] When the drill string reaches 20m below the sea surface, the pump is started, and the screw pressure drop and MWD measurement parameters are tested at different displacements. If the results are normal, the drill string continues to be lowered. Tests are conducted every 500m, and the test data is recorded. When the drill string is 10m away from the directional drilling rig, the heave compensation device is activated, and the pump is started at a low displacement. Based on the drill string azimuth obtained from the MWD measurement, the drill string azimuth is adjusted to be consistent with the azimuth of the drill string through hole. The drill string is lowered slowly. After the drill string passes the directional drilling rig, it is lowered slowly according to the length of the branch well casing in the multi-branch well structure. After bottoming out, the drill string is raised by 2m, and the pump is started at a normal displacement. The float shoes and cementing tools are drilled and ground. After the drill string drills out of the casing shoe, normal directional drilling is carried out to complete the branch well drilling operation.

[0067] Step 7: Pulling out the drill bit

[0068] After drilling the branch well to the designed depth, a thick plug is applied and circulated for two weeks. Then, normal drilling fluid is used to reverse the drilling and pull the drill string to the branch well casing. Next, the pipeline is switched to replace the seawater, the mud pump is turned up to increase the displacement, and the directional pump is repeatedly flushed. The ROV observes that the fluid returning from the subsea wellhead is clean. Then, reverse the drilling and pull the drill string back to the bottom of the branch well. After pulling out the drill string through hole, the drill string is circulated at a fixed point with a large displacement until the ROV observes that the fluid returning from the subsea wellhead is clean. Then, reverse the drilling and pull the drill string back to the bottom of the branch well. The sealing drilling fluid is introduced, the drill string is pulled out, and the branch well completion casing is assembled and run in. The casing hanger is set inside the branch well casing, and the first branch well is completed.

[0069] Step 8: Completion of remaining branch wells

[0070] Repeat steps six and seven above to complete the remaining branch wells;

[0071] Step 9: Feed the downslope into the tool string and adjust the downslope's orientation.

[0072] Connect the lifting sub, adapter, and retrieval sub. Lift the jack to the wellhead. Disconnect the lifting sub. Assemble the directional drilling tool string: 5-7 / 8″ drill pipe, adapter, stabilizer, adapter, 5-7 / 8″ drill pipe, adapter, and retrieval sub. Mark a vertical line on the bottom 5-7 / 8″ drill pipe of the directional drilling tool string. Lower the retrieval sub to a position 10m from the directional drilling tool. Activate the heave compensation device and record the drill string weight at this point. Unlock the drill string top drive to allow free rotation. Slowly lower the retrieval sub, observing the weight and drill string bottom depth from the subsea wellhead using the ROV. When the drill string is lowered to the bottom, the directional tool pin should be guided into the positioning key in the recovery section. Rotate the drill string forward 10°, then lift the drill string and observe the suspended weight. If the drill string suspended weight increases and the directional tool wet weight increases, it indicates that the directional tool and the recovery tool are successfully locked. Lift the directional tool and insert it into the drill string to disengage the blind plug from contact with the multi-branch well branch mechanism. Rotate the drill string clockwise or counterclockwise 120° to align the drill string through hole with the second branch well casing of the multi-branch well branch mechanism. Lower the directional tool to the multi-branch well branch mechanism. At the same time, check the drill string suspended weight to determine if the directional tool is in place by checking if the directional tool wet weight decreases. Unlock the top drive, reverse the drill string 10°, lift the drill string and insert the tool, and release the directional tool.

[0073] Step 10: Run the production test string to prepare for mining. Example 1

[0074] Connect the lifting sub, variable thread connector, and retrieval sub. Lift the jack to the wellhead, remove the lifting sub, and connect a 5-7 / 8″ drill pipe. Lift the directional guide box (containing the directional guide) to the wellhead, lower the retrieval sub, and connect and lock the directional guide. Connect the 5-7 / 8″ drill pipe, lower the directional guide, and control its lowering speed to prevent it from falling to the seabed due to sudden weight reduction. Mark the axial direction on several drill pipes near the underwater wellhead with white lines to prepare for subsequent drill pipe rotation and release. Lower the directional guide to 10m from the designed well depth, activate the drilling rig heave compensation, and adjust the directional guide's orientation so that the drill string through-hole aligns with the branch structure of the multi-branch well. With the branch wellbore azimuth aligned, after lowering the drill string into position, reverse the drill string 10°, lift and send in the tools, and release the directional drilling rig. Connect the following drilling tools to the branch wellbore: 8-1 / 2″ drill bit, 6-3 / 4″ bent housing screw, variable thread connector, 5-1 / 2″ non-magnetic weighted drill pipe, MWD, 5-1 / 2″ non-magnetic weighted drill pipe, variable thread connector, 5-1 / 2″ drill pipe, variable thread connector, and 5-7 / 8″ drill pipe to the drilling platform. When the drill string reaches 20m below sea level, start the pump and test the screw pressure drop and MWD measurement parameters at different displacements. If normal, continue lowering the drill string, testing every 500m and recording the test data. Lower the drill string until it is free from the azimuth. With 10m remaining at the directional drilling rig, activate the heave compensation device and start the pump at a low displacement. Based on the drill string azimuth measured by MWD, adjust the drill string azimuth to align with the through-hole azimuth. Lower the drill string slowly. After passing the directional drilling rig, lower it slowly according to the length of the branch well casing in the multi-branch well structure. After bottoming out, raise the drill string 2m, start the pump at normal displacement, and drill and grind the float shoes and cementing tools. After the drill string exits the casing shoe, proceed with normal directional drilling to complete the branch well drilling operation. After drilling the branch well to the designed depth, apply a thick plug and circulate it for two cycles. Then, switch to normal drilling fluid, back-ream the hole, and pull the drill string into the branch well casing. After switching the pipeline to seawater, the mud pump was increased to high displacement, and the directional drilling rig was repeatedly flushed. The ROV observed that the fluid returning from the subsea wellhead was clean. Then, the drilling was pulled out by back-row drilling, and the drill string was pulled out through the hole. The rig was then circulated at a fixed point with high displacement until the ROV observed that the fluid returning from the subsea wellhead was clean. The drilling was then pulled out by back-row drilling, and the directional drilling fluid was flushed at a fixed point with high displacement every 5m until the fluid returning from the subsea wellhead was clean. The drill string was then run down to the bottom of the branch well, and the sealing drilling fluid was introduced. The drill string was pulled out, and the completion casing of the branch well was assembled and run down. The casing hanger was set inside the casing of the branch well, and the first branch well was completed. Steps six and seven above were repeated to complete the remaining branch wells.Connect the lifting sub, adapter, and retrieval sub. Lift the lifting sub to the wellhead using a hoist. Disconnect the lifting sub and assemble the directional drilling tool string: 5-7 / 8″ drill pipe, adapter, stabilizer, adapter, 5-7 / 8″ drill pipe, adapter, and retrieval sub. Mark a vertical line on the bottom 5-7 / 8″ drill pipe of the directional drilling tool string. Lower the retrieval sub to a position 10m from the directional drilling tool. Activate the heave compensation device and record the drill string weight at this point. Unlock the drill string top drive to allow free rotation. Slowly lower the retrieval sub, observing the weight and bottom depth of the drill string from the subsea wellhead using the ROV. When the directional drilling tool string reaches the bottom... At this point, the directional guide pin should be engaged in the positioning key guide within the recovery sub. Rotate the tool string 10° clockwise, then lift the tool string and observe the suspended weight. If the drill string suspended weight increases and the directional guide's wet weight increases, it indicates successful locking between the directional guide and the recovery tool. Lift the directional guide into the tool string to disengage the blind plug from contact with the multi-branch well branch mechanism. Rotate clockwise or counterclockwise 120° to align the drill string through-hole with the casing of the second branch wellbore of the multi-branch well branch mechanism. Lower the directional guide to the multi-branch well branch mechanism. Simultaneously, check the drill string suspended weight to ensure the directional guide's wet weight has decreased before determining it is in place. Unlock the top drive, reverse the drill string 10°, lift the tool string, and release the directional guide. Lower the production test string to prepare for production. Example 2

[0075] To further improve the drilling efficiency of multi-branch wells containing marine hydrates, the directional drilling tool is pre-installed in the branch structure of the multi-branch well and lowered to the bottom of the well along with the casing. The only difference is that the release section body in the directional drilling tool is modified to a hollow structure, with a hollow inner diameter slightly larger than the section cylinder. The corresponding recovery guide inner diameter in the recovery section is also changed accordingly. The following construction method is adopted, including the following steps:

[0076] Step 1: After drilling to the designed well depth, pull out the drill string;

[0077] Step 2: Wellhead preparation, placing the directional device in the multi-branch well branch mechanism, and assembling the casing;

[0078] Step 3: Assemble the casing insertion tool and connect the casing insertion tool to the casing;

[0079] Step 4: Run the casing to the designed well depth;

[0080] Step 5: Cementing, cementing, and retrieving the delivery tools;

[0081] Step Six: Repeat steps five through ten in Example 1 to complete the drilling and completion of the multi-branch well.

[0082] Although embodiments of the present invention have been shown and described, these specific embodiments are merely explanations of the invention and are not intended to limit it. The specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. After reading this specification, those skilled in the art may make modifications, substitutions, and variations to the embodiments as needed without departing from the principles and spirit of the invention, but such modifications, substitutions, and variations are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for using a retrievable directional drilling tool in a multi-branch well drilling operation for natural gas hydrates, characterized in that: Includes the following steps: Step 1: Connect the slant and feed it into the tool string. Connect the lifting sub, the variable thread joint, and the recovery sub. Lift the lifting sub to the wellhead, remove the lifting sub, and connect a 5-7 / 8″ drill pipe. The recovery sub (6) has an internal thread (12) on one side and a recovery guide (9), a positioning key guide (10), and a positioning key sleeve (11) arranged sequentially from the outside to the inside on the other side. Step 2: Connect the slant gear The directional device box containing the directional device is hoisted to the wellhead, the retrieval sub is lowered, and the directional device is connected and locked. The directional device used in the multi-branch well drilling of natural gas hydrate includes a directional device body (1), a guide surface (5) is provided inside the directional device body (1), a release sub (7) is provided in the middle of the directional device body (1), and multiple sets of pins (8) are provided on the outer wall of the release sub (7). A drill bit through hole (4) is provided through the directional device body (1), and a blind plug (2) is connected to one side of the directional device body (1). Step 3: Insert the directional drilling rig into the casing of the branch well. Connect the 5-7 / 8″ drill pipe and lower the directional drill. Step 4: Adjust the orientation of the swashplate, then release the swashplate. The directional tool is sent to a depth of 10m from the designed well depth. The drilling rig heave compensation is activated, the directional tool is adjusted, and after it is lowered into place, the drill string is reversed 10°, the tool is pulled up and sent in, and the directional tool is released. Step 5: Connect the branch wellbore drilling tools Connecting drill string assembly for branch well drilling: 8-1 / 2″ drill bit, 6-3 / 4″ bent housing screw, variable thread connector, 5-1 / 2″ non-magnetic weighted drill pipe, MWD, 5-1 / 2″ non-magnetic weighted drill pipe, variable thread connector, 5-1 / 2″ drill pipe, variable thread connector, 5-7 / 8″ drill pipe to the drilling platform; Step Six: Drilling When the drill string reaches 20m below the sea surface, the pump is started, and the screw pressure drop and MWD measurement parameters are tested at different displacements. If the results are normal, the drill string continues to be lowered. Tests are conducted every 500m, and the test data is recorded. When the drill string is 10m away from the directional drilling rig, the heave compensation device is activated, and the pump is started at a low displacement. Based on the drill string azimuth obtained from the MWD measurement, the drill string azimuth is adjusted to be consistent with the azimuth of the drill string through hole. The drill string is lowered slowly. After the drill string passes the directional drilling rig, it is lowered slowly according to the length of the branch well casing in the multi-branch well structure. After bottoming out, the drill string is raised by 2m, and the pump is started at a normal displacement. The float shoes and cementing tools are drilled and ground. After the drill string drills out of the casing shoe, normal directional drilling is carried out to complete the branch well drilling operation. Step 7: Pulling out the drill bit After drilling the branch well to the designed depth, a thick plug is applied and circulated for two weeks. Then, normal drilling fluid is used to reverse the drilling and pull the drill string to the branch well casing. Next, the pipeline is switched to replace the seawater, the mud pump is turned up to increase the displacement, and the directional pump is repeatedly flushed. The ROV observes that the fluid returning from the subsea wellhead is clean. Then, reverse the drilling and pull the drill string back to the bottom of the branch well. After pulling out the drill string through hole, the drill string is circulated at a fixed point with a large displacement until the ROV observes that the fluid returning from the subsea wellhead is clean. Then, reverse the drilling and pull the drill string back to the bottom of the branch well. The sealing drilling fluid is introduced, the drill string is pulled out, and the branch well completion casing is assembled and run in. The casing hanger is set inside the branch well casing, and the first branch well is completed. Step 8: Completion of remaining branch wells Repeat steps six and seven above to complete the remaining branch wells; Step 9: Feed the downslope into the tool string and adjust the downslope's orientation. Connect the lifting sub, adapter, and retrieval sub. Lift the jack to the wellhead. Disconnect the lifting sub. Assemble the directional drilling tool string: 5-7 / 8″ drill pipe, adapter, stabilizer, adapter, 5-7 / 8″ drill pipe, adapter, and retrieval sub. Mark a vertical line on the bottom 5-7 / 8″ drill pipe of the directional drilling tool string. Lower the retrieval sub to a position 10m from the directional drilling tool. Activate the heave compensation device and record the drill string weight at this point. Unlock the drill string top drive to allow free rotation. Slowly lower the retrieval sub, observing the weight and drill string bottom depth from the subsea wellhead using the ROV. When the drill string is lowered to the bottom, the directional tool pin should be guided into the positioning key in the recovery section. Rotate the drill string forward 10°, then lift the drill string and observe the suspended weight. If the drill string suspended weight increases and the directional tool wet weight increases, it indicates that the directional tool and the recovery tool have been successfully locked. Lift the directional tool and insert it into the drill string to disengage the blind plug from contact with the multi-branch well branch mechanism. Rotate the drill string clockwise or counterclockwise 120° to align the drill string through hole with the casing of the second branch wellbore of the multi-branch well branch mechanism. Lower the directional tool to the multi-branch well branch mechanism. At the same time, check the drill string suspended weight to determine if the directional tool is in place by checking if the directional tool wet weight decreases. Unlock the top drive, reverse the drill string 10°, lift the drill string and insert the tool, and release the directional tool. Step 10: Run the production test string to prepare for mining.

2. The method for using a retrievable directional drilling tool in a multi-branch well drilling operation for natural gas hydrates according to claim 1, characterized in that: The outer surface of the inclined body (1) is provided with multiple sets of straightening strips (3).

3. The method for using a retrievable directional drilling tool in a multi-branch well drilling operation for natural gas hydrates according to claim 1, characterized in that: In step three, when the directional drilling tool slowly passes through the splash zone, the drilling speed should be slowed down, and the weight of the drill string should be recorded after the directional drilling tool enters the water.

4. The method for using a retrievable directional drilling tool in a multi-branch well drilling operation for natural gas hydrates according to claim 1, characterized in that: In step four, the directional drilling rig is sent to a depth of 10m from the designed well depth. The rig heave compensation is activated, the directional drilling rig is adjusted, and the directional drilling rig is slowly lowered to the designed well depth. At the same time, the wet weight of the directional drilling rig is reduced by the weight of the drill string to determine that it has been lowered into place. The drill string is reversed 10°, the tool is pulled up and sent in, and the directional drilling rig is released.

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