Underground coal mine large-diameter directional drilling system and hole forming method

Abstract

The invention discloses an underground coal mine large-diameter directional drilling system and a hole forming method. The system comprises a directional drill bit, a single-bend screw motor, a non-magnetic drilling tool, a packing cross short section, a double-wall drilling rod and a double-channel water injection and slag discharge device which are connected in sequence, and a mud pulse measurement-while-drilling instrument is arranged in the non-magnetic drilling tool; the packing crossed short section comprises a short section body and a limiting connector which are connected, and the outer wall of the short section body is sleeved with a sliding sleeve. A double-wall drill rod local reverse circulation mode is adopted for deslagging, compared with a conventional direct circulation mode, the circulating water amount needed for deslagging is greatly reduced, the water supply and pollution discharge requirements of a directional drilling site are greatly reduced, the rated discharge capacity and power of a matched slurry pump are greatly reduced, circulating water flows in an annular channel and a center channel of the double-wall drill rod, and the water supply efficiency is greatly improved. The overflow section is not influenced by the hole wall stratum, the reverse circulation flow deslagging efficiency is high, the cleaning effect in the hole is good, and the technical problems that the amount of circulating flushing liquid needed by a conventional large-diameter directional hole drilling system is large, and the hole wall stability maintaining capacity is poor are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground directional drilling in coal mines, and relates to a large-diameter directional drilling system and a hole-forming method. Specifically, it relates to a large-diameter directional drilling system and a hole-forming method for underground coal mines. Background Art

[0002] In recent years, with the continuous development, improvement and upgrading of the downhole measurement while drilling (MWD) directional drilling equipment in coal mines, the process technology has become increasingly mature, the scope and field of its application have been continuously broadened, and the application requirements faced have also been increasing. In addition to the generally increased hole-forming depth, there is an increasing demand for further increasing the borehole diameter. Typically, in the field of gas control, increasing the borehole diameter can improve the drainage effect, reduce the total number of holes arranged, and shorten the drainage time. Especially for the roof high-level directional boreholes used for mining-induced pressure relief gas drainage, increasing the diameter of the directional borehole has important practical significance for improving the drainage capacity, reducing the drilling workload, and improving the overall efficiency.

[0003] Previously, restricted by factors such as the small working space underground in coal mines, the special drilling construction angle, the low level of automation and intelligence of the drilling equipment system, and the lack of conditions for using large-diameter drill tools, the 'pilot hole + reaming' method was generally used to construct large-diameter boreholes. This technical method has the following prominent problems: the workload of single-hole repeated tripping is large, and the hole-forming cycle of multiple reamings is long; the trajectory of the directional pilot hole is curved, the stress condition of the drill tool during the drilling and reaming process is poor, the drill breakage accident is frequent, and the service life of the drill tool is short.

[0004] At present, the underground directional drilling technology and equipment in coal mines are developing towards the intelligent direction. The automatic drill pipe adding and unloading device, auxiliary hydraulic lifting device, large-opening clamping device, etc. have been developed, and the conditions for using large-diameter drill tool combinations with specifications of φ127mm and φ146mm have been met. The directional drilling construction ability has been greatly improved, and the once-through hole-forming diameter of the directional borehole has reached 200mm. However, during the process of once-through directional drilling of large-diameter holes, the amount of drill cuttings is large and the cross-sectional area of the annular flow in the borehole is large. In order to meet the requirements of cuttings discharge, the flow rate of the circulating flushing fluid is large during the construction process, and the rated displacement of the supporting mud pump (including the pump truck) is generally above 800L / min. The problems existing in the implementation of directional drilling using large-displacement mud pumps (including pump trucks) underground in coal mines are that the supporting water circulation system in the drill site is complex and huge, the required water supply is large, which often leads to difficult water supply in local areas of the mine and affects the mining and excavation production; the sewage discharge in the drill site is large, and the requirements for sewage discharge equipment and facilities are high. At the same time, as the diameter of the directional drilling hole increases, the stability of the borehole wall becomes worse. The clear water carrying the cuttings is discharged along the annulus between the drill pipe and the borehole wall, and the scouring and disturbance effect is strong, and the ability to maintain the stability of the borehole wall is poor. These factors have limited the application of the once-through drilling technology and equipment for large-diameter directional holes to a certain extent. How to reduce the amount of flushing fluid required for large-diameter directional hole construction and improve the stability of the borehole wall is still a major problem. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a large-diameter directional drilling system and a hole-forming method for underground coal mines, so as to solve the technical problems of large amount of circulating flushing fluid required by the conventional drilling system for large-diameter directional holes and poor ability to maintain the stability of the hole wall.

[0006] To solve the above technical problems, the present invention is implemented by the following technical solutions:

[0007] A large-diameter directional hole drilling system for underground coal mines includes a directional drill bit, a single-bend positive displacement motor, non-magnetic drill collars, a packer crossover sub, double-wall drill pipes, and a dual-channel water injection and slag discharge device connected in sequence. A mud pulse measurement-while-drilling instrument is provided in the non-magnetic drill collars;

[0008] The packer crossover sub includes a sub body and a limit joint connected to each other. A sliding sleeve is sleeved on the outer wall of the sub body, and an inner pipe is arranged in the sub body; the limit joint is connected to the non-magnetic drill collars, and the sub body is connected to the double-wall drill pipes;

[0009] The sub body includes a cylinder. A plurality of fixed sector-shaped wing plates are equidistantly arranged on the outer wall of the cylinder, and the outer contour diameter of the fixed sector-shaped wing plates is the same as the diameter of the directional drill bit;

[0010] A cavity is arranged at the front end of the cylinder in the axial direction, a stepped blind hole is arranged at the rear end of the cylinder in the axial direction, and a plurality of arc-shaped hole channels are radially opened on the outer side of the middle part of the cylinder in the axial direction. The arc-shaped hole channels communicate the stepped blind hole with the cavity; and the arc-shaped hole channels are located on the cylinder between the fixed sector-shaped wing plates; a plurality of inclined holes are equidistantly arranged along the circumferential direction in the middle part of the cylinder in the axial direction, and each inclined hole communicates the stepped blind hole with the outside of the cylinder; the orifice of the inclined hole on the outer wall of the cylinder is close to the cavity; the central axis of the inclined hole coincides with the axial central plane of the fixed sector-shaped wing plate;

[0011] The sliding sleeve includes a first cylinder. A plurality of sliding sector-shaped wing plates are evenly arranged on the outer wall of the first cylinder, and the outer contour diameter of the plurality of sliding sector-shaped wing plates is the same as the outer contour diameter of the plurality of fixed sector-shaped wing plates on the sub body; a wedge-shaped claw is arranged on one side of each of the plurality of sliding sector-shaped wing plates close to the limit joint;

[0012] The inner pipe includes a second cylinder. A plurality of centralizer blocks are evenly arranged on the outer wall of the second cylinder, and the outer contour diameter of the centralizer blocks is the same as the diameter of the middle section of the stepped blind hole on the sub body;

[0013] A connecting cylinder is arranged on the inner wall of one end of the second cylinder, and the connecting cylinder is in fit connection with the stepped blind hole on the sub body.

[0014] The present invention further includes the following technical features:

[0015] An abnormal key is provided on the outer wall of the short joint located between adjacent fixed sector wing plates, and an abnormal guide groove is provided on the inner wall of the sliding sleeve at the circumferential position where the sliding sector wing plate is provided. The abnormal guide groove cooperates with the abnormal key.

[0016] The outer contour surface of the abnormal key is in the shape of an arc or an elliptical arc.

[0017] The radially outer side wall of the wedge-shaped claw is an inclined surface.

[0018] The limiting joint includes a third cylinder. A limiting convex ring is provided in the middle of the outer wall of the third cylinder, and external threads are provided on the outer walls at both ends of the third cylinder.

[0019] A method for forming a large-diameter directional long borehole in a coal mine underground. This method uses the large-diameter directional borehole drilling system in the coal mine underground and specifically includes the following steps:

[0020] Step 1, hole opening and pipe lowering:

[0021] Adopt rotary drilling to open a hole to obtain a drilled hole in the hole opening section. Lower a sealing pipe into the drilled hole in the hole opening section, and inject an expansive concrete slurry between the outer wall of the sealing pipe and the hole wall of the drilled hole in the hole opening section to form a sealing body.

[0022] Step 2, lower the large-diameter directional borehole drilling system in the coal mine underground into the sealing pipe and perform tool face correction;

[0023] A drilled hole annulus inner section is formed between the large-diameter directional borehole drilling system in the coal mine underground and the hole wall of the to-be-formed directional hole;

[0024] Step 3, add a double-wall drill pipe to the sealing and crossing short joint in the large-diameter directional borehole drilling system in the coal mine underground. Install a hole mouth device on the sealing pipe, and install a dual-channel water injection and slag discharge device and a control drilling execution device on the double-wall drill pipe passing through the hole mouth device.

[0025] The liquid injection port of the hole mouth device is connected to an external liquid injection pump through a liquid injection pipe; a control valve is installed on the liquid outlet of the hole mouth device, and a return liquid pipe is connected to the control valve.

[0026] The annulus channel of the double-wall drill pipe is a high-pressure water flow channel, and the flow direction is from the hole mouth to the hole bottom;

[0027] The central channel of the double-wall drill pipe is a reflux channel, and the flow direction is from the hole bottom to the hole mouth;

[0028] The space between the double-wall drill pipe and the hole wall is the drilled hole annulus outer section. The drilled hole annulus outer section is communicated with the inside of the hole mouth device; the drilled hole annulus outer section is a protection hole liquid filling and intermittent flow channel, and the flow direction is from the hole mouth to the hole bottom.

[0029] The interior of the water inlet passage of the double-channel water injection and slag discharge device is communicated with the annular space passage of the double-wall drill pipe. A high-pressure water pipe is connected to the exterior of the water inlet passage, and the end of the high-pressure water pipe is connected to a mud pump; the interior of the return passage of the double-channel water injection and slag discharge device is communicated with the central passage of the double-wall drill pipe. A return water pipe is connected to the exterior of the return passage, and the end of the return water pipe is connected to an external gas-liquid separation device;

[0030] Step Four: Start the liquid injection pump. The liquid injection pump injects hole protection fluid into the outer section of the drilling annulus. After it is filled, adjust the liquid injection speed and feedback pressure; start the mud pump. The mud pump injects high-pressure water into the annular space passage of the double-wall drill pipe. The high-pressure water reaches the bottom of the hole to drive the single-bend screw motor to do work, and then returns out through the central passage of the double-wall drill pipe;

[0031] Step Five: Directional drilling:

[0032] Control the drilling execution device to drive the downhole drill string assembly to feed and rotate, and implement the compound directional drilling process. During the drilling process, the sliding sector wing plate on the sealing crossover sub slides along the axial direction of the borehole towards the direction close to the fixed sector wing plate until the fixed sector wing plate and the sliding sector wing plate are in contact, closing the outer axial channel, cutting off the connection between the outer section of the drilling annulus and the inner section of the drilling annulus. The outer section of the drilling annulus is filled with hole protection fluid, and the inner section of the drilling annulus conducts circulating slag discharge. The multiphase fluid returning through the central passage of the double-wall drill pipe enters the gas-liquid separation device through a rubber hose. The gas enters the negative pressure pipe, and the drill cuttings enter the sewage tank with water through the slag discharge pipe;

[0033] Step Six: End-hole and drill string withdrawal:

[0034] When the construction reaches the designed depth, a large-diameter directional hole is obtained, and the double-wall drill pipe and the underground coal mine large-diameter directional hole drilling system are withdrawn in sequence;

[0035] Step Seven: Pipe lowering and continuous pumping:

[0036] Lower a hole protection pipe into the large-diameter directional hole, remove the hole mouth device, and connect a negative pressure drainage pipeline to the sealing pipe for gas drainage.

[0037] Between Step Five and Step Six, it also includes: performing external circulation flushing for auxiliary slag discharge at intervals of 100 m to 150 m. Specifically:

[0038] Lift the underground coal mine large-diameter directional hole drilling system 2 m to 5 m away from the bottom of the hole, so that the fixed sector wing plate and the sliding sector wing plate on the sealing crossover sub are disengaged, and the outer axial channel is opened. Stop the water supply of the mud pump, adjust the displacement of the liquid injection pump to about 200 L / min, close the control valve on the hole mouth device, and the hole protection fluid flows from the hole mouth to the bottom of the hole in the outer section of the drilling annulus, carrying the sediment and entering the central channel of the drill pipe through the inclined hole channel at the sealing crossover sub and returning out.

[0039] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0040] (Ⅰ) For the large-diameter directional drilling system in coal mines of the present invention, the local reverse circulation method of double-wall drill pipes is adopted for slag discharge. Compared with the conventional positive circulation, the circulating water volume required for slag discharge is greatly reduced, the requirements for water supply and sewage discharge in the directional drilling site are greatly reduced, the rated displacement and power of the supporting mud pump are greatly reduced, the circulating water flows in the annular channel and the central channel of the double-wall drill pipe, and the flow cross-section is not affected by the formation of the borehole wall. The reverse circulation slag discharge has high efficiency and good hole cleaning effect, solving the technical problems of large circulating flushing fluid volume required by the conventional drilling system for large-diameter directional holes and poor ability to maintain borehole wall stability.

[0041] (Ⅱ) For the large-diameter directional long borehole drilling method in coal mines of the present invention, there are two kinds of liquids in the borehole during the drilling process. The space between the drill pipe and the borehole wall is filled with hole protection fluid, which greatly improves the stability of the borehole wall. The probability of borehole wall collapse can be reduced by more than 20%, and the probability of mudstone diameter shrinkage can be reduced by more than 90%.

[0042] (Ⅲ) For the large-diameter directional long borehole drilling method in coal mines of the present invention, different slag discharge circulation methods can be flexibly switched. Under the condition of large borehole diameter, the slag discharge capacity is strong, and the comprehensive hole-forming efficiency of large-diameter long borehole directional drilling can be increased by about 10%.

[0043] (Ⅳ) The construction borehole diameter of the drill string system supporting the large-diameter long borehole directional drilling method in coal mines of the present invention can be flexibly changed. Within a certain borehole diameter range, different diameter boreholes can be constructed only by replacing the directional drill bit and the supporting sealing and crossing short joint. The auxiliary equipment system is relatively simple and the comprehensive operation cost is low. Brief Description of the Drawings

[0044] Figure 1 It is a schematic structural diagram of the drill string system supporting the large-diameter directional long borehole.

[0045] Figure 2 It is a schematic structural diagram of the sealing and crossing short joint.

[0046] Figure 3 It is a schematic structural diagram of the short joint body in the separating and crossing short joint.

[0047] Figure 4 It is a schematic structural diagram of the sliding sleeve in the separating and crossing short joint.

[0048] Figure 5 It is a schematic structural diagram of the inner pipe in the separating and crossing short joint.

[0049] Figure 6 It is a schematic structural diagram of the limit joint in the separating and crossing short joint.

[0050] Figure 7Schematic diagram of the circulation flow path at the sealing crossover sub during directional drilling.

[0051] Figure 8 Schematic diagram of the circulation flow path at the sealing crossover sub during circulation flushing.

[0052] Figure 9 Schematic diagram of the principle of the large-diameter directional long borehole drilling system and hole-forming method in coal mines.

[0053] Figure 10 Profile trajectory diagram of the large-diameter directional hole in this embodiment.

[0054] The meanings of each label in the figure are as follows: 1 - directional drill bit, 2 - single-bend positive displacement motor, 3 - non-magnetic drill pipe, 4 - mud pulse measurement-while-drilling instrument, 5 - sealing crossover sub, 6 - double-wall drill pipe, 7 - double-channel water injection and slag discharge device, 8 - drilling execution device, 9 - hole mouth device, 10 - mud pump, 11 - liquid injection pump, 12 - gas-liquid separation device, 13 - sewage sump, 14 - hole sealing pipe, 15 - sealing solid, 16 - control valve, 17 - return liquid pipe, 18 - liquid injection pipe, 19 - high-pressure water pipe, 20 - return water pipe, 21 - slag discharge pipe, 22 - negative pressure pipe, 23 - annulus channel, 24 - central channel, 25 - outer section of the drilling annulus, 26 - inner section of the drilling annulus;

[0055] 501 - short section body, 502 - sliding sleeve, 503 - limit joint, 504 - inner pipe;

[0056] 601 - inner drill pipe, 602 - outer drill pipe;

[0057] 701 - water inlet channel, 702 - return channel;

[0058] 901 - liquid outlet, 902 - liquid injection port;

[0059] 5011 - cylinder, 5012 - fixed sector wing plate, 5013 - special-shaped key, 5014 - cavity, 5015 - stepped blind hole, 5016 - inclined hole, 5017 - arc-shaped hole flow path;

[0060] 5021 - first cylinder, 5022 - sliding sector wing plate, 5023 - wedge-shaped claw, 5025 - special-shaped guide groove;

[0061] 5031 - connection end, 5032 - limit convex ring, 5033 - central through hole;

[0062] 5041 - second cylinder, 5042 - centralizing block, 5044 - connecting cylinder.

[0063] The following further explains the specific content of the present invention in detail in conjunction with embodiments. Specific embodiments

[0064] It should be noted that all components in the present invention are components known in the art without special instructions.

[0065] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solutions of this application fall within the protection scope of the present invention.

[0066] The present invention provides a large-diameter directional drilling system for coal mines underground, as Figures 1 to 6 shown, which includes a directional drill bit 1, a single-bend positive displacement motor 2, a non-magnetic drill collar 3, a packer crossover sub 5, a double-wall drill pipe 6, and a double-channel water injection and slag discharge device 7 connected in sequence. A mud pulse measurement-while-drilling instrument 4 is arranged in the non-magnetic drill collar 3;

[0067] The packer crossover sub 5 includes a sub body 501 and a limit joint 503 connected to each other. A sliding sleeve 502 is sleeved on the outer wall of the sub body 501, and an inner pipe 504 is arranged in the sub body 501; the limit joint 503 is connected to the non-magnetic drill collar 3, and the sub body 501 is connected to the double-wall drill pipe 6;

[0068] The sub body 501 includes a cylinder 5011. A plurality of fixed sector-shaped wing plates 5012 are arranged on the outer wall of the cylinder 5011 at equal intervals, and the outer contour diameter of the fixed sector-shaped wing plates 5012 is the same as the diameter of the directional drill bit 1;

[0069] A cavity 5014 is arranged at the axial front end of the cylinder 5011, a stepped blind hole 5015 is arranged at the axial rear end of the cylinder 5011, and a plurality of arc-shaped hole channels 5017 are opened on the radial outer side of the middle part of the cylinder 5011 in the axial direction. The arc-shaped hole channels 5017 communicate the stepped blind hole 5015 with the cavity 5014; and the arc-shaped hole channels 5017 are located on the cylinder 5011 between the fixed sector-shaped wing plates 5012; a plurality of inclined holes 5016 are arranged on the middle part of the cylinder 5011 in the axial direction at equal intervals in the circumferential direction. Each inclined hole 5016 communicates the stepped blind hole 5015 with the outside of the cylinder 5011; the orifice of the inclined hole 5016 on the outer wall of the cylinder 5011 is close to the cavity 5014; the central axis of the inclined hole 5016 coincides with the axial central plane of the fixed sector-shaped wing plate 5012;

[0070] The sliding sleeve 502 includes a first cylinder 5021. A plurality of sliding sector-shaped wing plates 5022 are evenly arranged on the outer wall of the first cylinder 5021, and the outer contour diameter of the plurality of sliding sector-shaped wing plates 5022 is the same as the outer contour diameter of the plurality of fixed sector-shaped wing plates 5012 on the sub body 501; a wedge-shaped claw 5023 is arranged on one side of the plurality of sliding sector-shaped wing plates 5022 close to the limit joint 503;

[0071] The inner pipe 504 includes a second cylinder 5041, on the outer wall of which a plurality of centralizing blocks 5042 are evenly arranged. The outer contour diameter of the centralizing block 5042 is the same as the diameter of the middle section of the stepped blind hole 5015 on the short joint body 501.

[0072] One end of the inner wall of the second cylinder 5041 is provided with a connecting cylinder 5044, which is in fit connection with the stepped blind hole 5015 on the short joint body 501.

[0073] In the above technical solution, for the large-diameter directional drilling system in coal mines, the local reverse circulation method of double-wall drill pipes is adopted for slag discharge. Compared with the conventional positive circulation, the circulating water volume required for slag discharge is greatly reduced, the water supply and sewage discharge requirements of the directional drill site are greatly reduced, the rated displacement and power of the supporting mud pump are greatly reduced, the circulating water flows in the annular channel and the central channel of the double-wall drill pipe, and the cross-sectional area of the flow is not affected by the formation of the hole wall. The reverse circulation slag discharge has high efficiency and good hole cleaning effect, solving the technical problems of large circulating flushing fluid volume required by the conventional drilling system for large-diameter directional holes and poor ability to maintain the stability of the hole wall.

[0074] Taking the actual drilling test of a 200-mm diameter borehole as an example, for the slag discharge drilling by the conventional drill pipe positive circulation method, the required instantaneous circulating water volume is more than 720 L / min, while for the slag discharge drilling by the local reverse circulation method of double-wall drill pipes, the required instantaneous water volume is about 350 L / min, reducing by more than 50%, greatly reducing the water supply and sewage discharge requirements of the directional drill site, and greatly reducing the rated displacement and power of the supporting mud pump.

[0075] The function of the fixed sector wing plate is to separate the flow channel between the drill tool and the hole wall, so its diameter cannot be less than the diameter of the drill bit. The function of the sliding sector wing plate is the same as that of the fixed sector wing plate, separating the flow channel between the drill tool and the hole wall.

[0076] Figure 7 The figure shows a schematic diagram of the flow channel at the sealing crossover short joint during directional drilling. During the drilling process, under the action of friction, the sliding sleeve 502 abuts against the fixed sector wing plate 5012 on the short joint body 501. The wing plates of the two are arranged in a crossed manner and form a sealing body in the circumferential direction, dividing the channel between the drill tool and the hole wall into the outer section 25 of the borehole annulus and the inner section 26 of the borehole annulus. The outer section 25 of the borehole annulus is filled with hole protection fluid; the circulating water flows through the annular channel 23 of the double-wall drill pipe 6 (the space between the inner pipe 601 and the outer pipe 602 of the drill pipe) to the bottom of the hole, enters the central channel of the limit short joint 503 and the non-magnetic drill pipe 3 after passing through the short joint body 501, drives the positive displacement motor to do work and then carries the drill cuttings into the inner section 26 of the borehole annulus, flows to the sealing crossover short joint 5 and enters the central channel 24 of the double-wall drill pipe through the inclined hole 5016 to form an inner-layer reverse circulation flow; during the compound directional drilling process, the wedge-shaped claws 5023 on the sliding sleeve 502 can assist in agitating the drill cuttings to make them enter the inclined hole channel 5016 with the water flow, and at the same time have the function of crushing large-particle drill cuttings.

[0077] Figure 8 The figure shows a schematic diagram of the circulation flow path at the packer crossover sub during cyclic punching. During the process of pulling back the drill string in the hole, the sliding sleeve 502 abuts against the limit joint 503 under the action of friction. The fixed sector wing plate 5012 and the sliding sector wing plate 5022 are axially separated, and the packing function fails. The outer section 25 of the drilling annulus and the inner section 26 of the drilling annulus are communicated with each other. The hole protection fluid can be continuously injected into the hole through the outer section 25 of the drilling annulus, and enters the central channel 24 of the drill pipe through the inclined hole channel 5016 at the packer crossover sub to form a reverse circulation flow, which can assist in slag discharge.

[0078] A special-shaped key 5013 is arranged on the outer wall of the short joint body 501 between adjacent fixed sector wing plates 5012. A special-shaped guiding groove 5025 is arranged on the inner wall of the sliding sleeve 502 provided with the sliding sector wing plate 5022, and the special-shaped guiding groove 5025 cooperates with the special-shaped key 5013.

[0079] In the above technical solution, the key connection is stable and convenient.

[0080] The outer contour surface of the special-shaped key 5013 is in the shape of an arc or an elliptical arc.

[0081] The radially outer side wall of the wedge-shaped claw 5023 is an inclined surface.

[0082] In the above technical solution, the inclined surface is provided to break large-particle drill cuttings.

[0083] The limit joint 503 includes a third cylinder 5033. A limit convex ring 5032 is arranged in the middle of the outer wall of the third cylinder 5033, and external threads 5031 are provided on the outer walls at both ends of the third cylinder 5033.

[0084] In the above technical solution, the external threads 5031 are used to connect the limit joint 503 and the non-magnetic drill 3.

[0085] The present invention also provides a method for forming a large-diameter directional long borehole in a coal mine. This method uses a large-diameter directional borehole drilling system in a coal mine, and specifically includes the following steps:

[0086] Step 1, hole opening and pipe lowering:

[0087] Adopt rotary drilling to open a hole to obtain a drilled hole in the hole opening section. Lower a sealing pipe 14 into the drilled hole in the hole opening section, and inject an expansive concrete slurry between the outer wall of the sealing pipe 14 and the hole wall of the drilled hole in the hole opening section to form a sealing body 15;

[0088] Step 2, lower the large-diameter directional borehole drilling system in the coal mine into the sealing pipe 14 and perform tool face correction;

[0089] An inner section 26 of a drilling annulus is formed between a large-diameter directional drilling system in a coal mine and the hole wall of a to-be-formed directional hole.

[0090] Step 3: A double-wall drill pipe 6 is connected to a sealing crossover nipple 5 in the large-diameter directional drilling system in the coal mine. An orifice device 9 is installed at the installation hole of a sealing pipe 14. A dual-channel water injection and slag discharge device 7 and a controlled drilling execution device 8 are installed on the double-wall drill pipe 6 passing through the orifice device 9.

[0091] A liquid injection port 902 of the orifice device 9 is connected to an external liquid injection pump 11 through a liquid injection pipe 18. A control valve 16 is installed at a liquid outlet 901 of the orifice device 9, and a return liquid pipe 17 is connected to the control valve 16.

[0092] An annular space channel 23 of the double-wall drill pipe 6 is a high-pressure water flow channel, and the flow direction is from the orifice to the hole bottom.

[0093] A central channel 24 of the double-wall drill pipe 6 is a reflux channel, and the flow direction is from the hole bottom to the orifice.

[0094] An outer section 25 of the drilling annulus is formed between the double-wall drill pipe 6 and the hole wall. The outer section 25 of the drilling annulus is communicated with the inside of the orifice device 9. The outer section 25 of the drilling annulus is a protection hole fluid filling and intermittent flow channel, and the flow direction is from the orifice to the hole bottom.

[0095] The inside of an inlet channel 701 of the dual-channel water injection and slag discharge device 7 is communicated with the annular space channel 23 of the double-wall drill pipe 6. A high-pressure water pipe 19 is connected to the outside of the inlet channel 701, and the end of the high-pressure water pipe 19 is connected to a mud pump 10. The inside of a return channel 702 of the dual-channel water injection and slag discharge device 7 is communicated with the central channel 24 of the double-wall drill pipe 6. A return water pipe 20 is connected to the outside of the return channel 702, and the end of the return water pipe 20 is connected to an external gas-liquid separation device 12.

[0096] Step 4: Start the liquid injection pump 11. The liquid injection pump 11 injects protection hole fluid into the outer section 25 of the drilling annulus. After filling, adjust the liquid injection speed and feedback pressure. Start the mud pump 10. The mud pump 10 injects high-pressure water into the annular space channel 23 of the double-wall drill pipe 6. The high-pressure water reaches the hole bottom to drive the single-bend screw motor 2 to work, and then returns through the central channel 24 of the double-wall drill pipe 6.

[0097] Step 5: Directional drilling:

[0098] The control drilling execution device 8 is driven to feed and rotate the downhole drill string assembly, implementing the compound directional drilling process. During drilling, the sliding sector wing plate 5022 on the sealing crossover sub 5 slides axially along the borehole towards the fixed sector wing plate 5012 until the fixed sector wing plate 5012 and the sliding sector wing plate 5022 are in contact, closing the outer axial channel. The outer section 25 of the borehole annulus is separated from the inner section 26 of the borehole annulus. The outer section 25 of the borehole annulus is filled with hole protection fluid, and the inner section 26 of the borehole annulus is used for circulating slag discharge. The multiphase fluid returned through the central channel 24 of the double-wall drill pipe 6 enters the gas-liquid separation device 12 through the rubber hose 20. The gas enters the negative pressure pipe 22, and the drill cuttings enter the sewage tank 13 with water through the slag discharge pipe 21;

[0099] Step Six, withdrawing the drill at the end of the hole:

[0100] When the construction reaches the designed depth, a large-diameter directional hole is obtained, and the double-wall drill pipe 6 and the underground coal mine large-diameter directional hole drilling system are withdrawn in sequence;

[0101] Step Seven, lowering the pipe and connecting for pumping:

[0102] A hole protection pipe is lowered into the large-diameter directional hole, the hole mouth device 9 is removed, and a negative pressure drainage pipeline is connected to the sealing pipe 14 for gas drainage.

[0103] In the above technical solution, for the underground coal mine large-diameter directional long borehole drilling method, there are two kinds of liquids in the borehole during drilling. The space between the drill pipe and the borehole wall is filled with hole protection fluid, which greatly improves the stability of the borehole wall. The probability of borehole wall collapse can be reduced by more than 20%, and the probability of shale diameter shrinkage can be reduced by more than 90%.

[0104] The underground coal mine large-diameter directional long borehole drilling method can flexibly switch to implement different slag discharge circulation methods. Under the condition of large boreholes, the slag discharge capacity is strong, and the comprehensive hole-forming efficiency of large-diameter long borehole directional drilling can be increased by about 10%.

[0105] The drill string system supporting the underground coal mine large-diameter long borehole directional drilling method has a flexible variable construction hole diameter. Within a certain hole diameter range, only the directional drill bit and the supporting sealing crossover sub need to be replaced to construct boreholes with different diameters. The auxiliary equipment system is relatively simple, and the comprehensive operation cost is low.

[0106] Figure 9The figure shows a schematic diagram of the principle of a large-diameter directional long borehole drilling system and a hole-forming method in underground coal mines. The drilling tool system from the bottom of the hole outwards is successively a directional bit 1, a single-bend positive displacement motor 2, a non-magnetic drill pipe 3 (equipped with a mud pulse measurement-while-drilling instrument 4 inside), a packer crossover sub 5, a double-wall drill pipe 6, and a double-channel water injection and slag discharge device 7. The drilling execution device 8 drives actions such as feeding, rotation, adjusting the tool face, and withdrawing the drill. A sealing pipe 14 is inserted into the hole section at the hole opening. After grouting, a sealing body 15 is formed between the sealing pipe and the hole wall, creating conditions for sealing and bearing pressure between the hole wall and the drill pipe. A hole-opening device 9 is installed on the sealing pipe 14, whose core function is to seal the gap between the double-wall drill pipe 6 and the hole wall. At the same time, a liquid outlet 901 and a liquid injection port 902 are provided on the hole-opening device 9. The liquid injection port 902 is connected to a liquid injection pump through a liquid injection pipe 18, used to inject hole protection fluid into the outer section 25 of the drilling annulus. The liquid outlet 901 is connected to a control valve 16, and is led to a sewage sump 13 through a return liquid pipe 17. The double-channel water injection and slag discharge device 7 is provided with a water inlet channel 701 and a return channel 702. The water inlet channel 701 is connected to the annulus channel 23 of the double-wall drill pipe 6, and is simultaneously connected to a mud pump 10 through a high-pressure water pipe 19. The return channel 702 is connected to the central channel 24 of the double-wall drill pipe 6, and is simultaneously connected to a gas-liquid separation device 12 through a rubber hose 20. A negative pressure pipe 22 is connected to the gas-liquid separation device 12 to discharge the gas discharged with the circulating water, and a slag discharge pipe 21 is connected to lead the circulating water and drill cuttings into the sewage sump 13.

[0107] Preferably, for a directional hole with a diameter of 193 mm to 200 mm, the drilling diameter of the opening section is expanded to 285 mm to 300 mm according to the formation characteristics, the depth is more than 12 m, and a sealing pipe 14 with an outer diameter of 244.5 mm is inserted into the drilling of the opening section.

[0108] The total length of the large-diameter directional hole drilling system in underground coal mines is between 7.5 m and 8 m, and the hole-forming diameter is 193 mm to 200 mm. This section is a single-cycle system, with a high-pressure water flow channel in the center, and the flow direction is from the packer crossover sub 5 to the directional bit 1; the inner section 26 of the drilling annulus is a circulating water and slag discharge flow channel, and the flow direction is from the directional bit 1 to the packer crossover sub 5. After the downhole directional drill string assembly is lowered into the hole, the tool face is corrected.

[0109] The diameter of the liquid injection pipe 18 is not less than 25 mm; the diameter of the return liquid pipe 17 is not less than 32 mm; the liquid outlet pressure range of the control valve 16 is 0.1 MPa to 0.5 MPa; the double-wall drill pipe 6 has an outer diameter of 127 mm or 146 mm, and a multi-cycle system is arranged between the hole-opening device 9 and the packer crossover sub 5;

[0110] Step 4: Start the liquid injection pump 11. The liquid injection pump 11 injects hole protection fluid into the outer section 25 of the borehole annulus. After filling, adjust the injection speed to be between 5 L / min and 15 L / min, and the feedback pressure is about 0.1 MPa. Start the mud pump 10. The mud pump 10 injects high-pressure water into the annulus channel 23 of the double-wall drill pipe 6 at a displacement between 300 L / min and 350 L / min. The high-pressure water reaches the bottom of the hole to drive the single-bend screw motor 2 to do work, and then returns through the central channel 24 of the double-wall drill pipe 6.

[0111] In Step 5: Drill directionally according to the designed trajectory to obtain a large-diameter hole. As the hole depth increases, the hole protection fluid filled outside the hole between the hole mouth and the packer crossover sub and outside the double-wall drill pipe increases synchronously.

[0112] In Step 6: During the process of withdrawing the drill, according to the formation conditions, inject and circulate the hole protection fluid into the hole once every 50 m to 60 m to maintain the stability of the hole wall.

[0113] In Step 7: The outer diameter of the hole protection pipe is 89 mm or larger.

[0114] Between Step 5 and Step 6, it also includes: conduct an external circulation flushing to assist in removing slag every 100 m to 150 m. Specifically:

[0115] Lift the large-diameter directional hole drilling system in the coal mine underground 2 m to 5 m from the bottom of the hole, so that the fixed sector wing plates 5012 and the sliding sector wing plates 5022 on the packer crossover sub 5 are disengaged, and the outer axial channel is opened. Stop the water supply of the mud pump 10, adjust the displacement of the liquid injection pump 11 to about 200 L / min, close the control valve 16 on the hole mouth device 9, and the hole protection fluid flows from the hole mouth to the bottom of the hole in the outer section 25 of the borehole annulus, carrying the sediment and entering the central channel 24 of the drill pipe through the inclined hole channel 5016 at the packer crossover sub 5 and then returning.

[0116] In the above technical solution, during the directional drilling process, when drill cuttings appear in the outer section 25 of the borehole annulus and the cleaning effect deteriorates due to factors such as the increase in borehole depth, formation changes, and adjustment of the performance of the hole protection fluid, conduct an external circulation flushing to assist in removing slag once.

[0117] Example:

[0118] In a certain mine in Shanxi, the roof high-level large-diameter directional hole encounters complex formations: local fragmentation, hydration swelling of mud shale, poor hole wall stability during the conventional directional drilling process, frequent complex situations such as hole collapse and mudstone diameter reduction in the hole, shallow hole formation depth, and the maximum hole depth does not exceed 300 m. Using the large-diameter directional hole drilling method of the present invention, with the help of the hole protection fluid and the reverse circulation slag removal process, the stability of the hole wall is improved, and the hole formation depth reaches more than 450 m. The actual drilling profile trajectory is as Figure 10 shown.

Claims

1. A large-diameter directional drilling system for underground coal mines, comprising a directional drill bit (1), a single-bend positive displacement motor (2), a non-magnetic drill string (3), a packer crossover sub (5), a double-wall drill pipe (6) and a dual-channel water injection and slag discharge device (7) connected in sequence. A mud pulse measurement-while-drilling instrument (4) is disposed in the non-magnetic drill string (3). It is characterized in that The packer crossover sub (5) includes a sub body (501) and a limit joint (503) connected to each other. A sliding sleeve (502) is sleeved on the outer wall of the sub body (501). An inner pipe (504) is disposed in the sub body (501). The limit joint (503) is connected to the non-magnetic drill string (3), and the sub body (501) is connected to the double-wall drill pipe (6). The sub body (501) includes a cylinder (5011). A plurality of fixed sector-shaped wing plates (5012) are equidistantly arranged on the outer wall of the cylinder (5011), and the outer contour diameter of the fixed sector-shaped wing plates (5012) is the same as the diameter of the directional drill bit (1). A cavity (5014) is provided at the axial front end of the cylinder (5011), a stepped blind hole (5015) is provided at the axial rear end of the cylinder (5011), and a plurality of arc-shaped hole channels (5017) are radially provided on the outer side of the middle part of the cylinder (5011) in the axial direction. The arc-shaped hole channels (5017) communicate the stepped blind hole (5015) with the cavity (5014). The arc-shaped hole channels (5017) are located on the cylinder (5011) between the fixed sector-shaped wing plates (5012). A plurality of inclined holes (5016) are equidistantly arranged along the circumferential direction in the middle part of the cylinder (5011) in the axial direction. Each inclined hole (5016) communicates the stepped blind hole (5015) with the outside of the cylinder (5011). The orifice of the inclined hole (5016) on the outer wall of the cylinder (5011) is close to the cavity (5014). The central axis of the inclined hole (5016) coincides with the axial central plane of the fixed sector-shaped wing plate (5012). The sliding sleeve (502) includes a first cylinder (5021). A plurality of sliding sector-shaped wing plates (5022) are evenly arranged on the outer wall of the first cylinder (5021). The outer contour diameters of the plurality of sliding sector-shaped wing plates (5022) are the same as the outer contour diameters of the plurality of fixed sector-shaped wing plates (5012) on the sub body (501). Wedge-shaped claws (5023) are arranged on one side of the plurality of sliding sector-shaped wing plates (5022) close to the limit joint (503). The inner pipe (504) includes a second cylinder (5041). A plurality of centralizer blocks (5042) are evenly arranged on the outer wall of the second cylinder (5041). The outer contour diameter of the centralizer blocks (5042) is the same as the diameter of the middle section of the stepped blind hole (5015) on the sub body (501). One end inner wall of the second cylinder (5041) is provided with a connecting cylinder (5044), and the connecting cylinder (5044) is in mating connection with a stepped blind hole (5015) on the short joint body (501).

2. The large-diameter directional drilling system for coal mines underground according to claim 1, wherein An irregular key (5013) is provided on the outer wall of the short joint body (501) located between adjacent fixed sector vanes (5012), and an irregular guide groove (5025) is provided on the inner wall of the sliding sleeve (502) at the circumferential position where the sliding sector vane (5022) is provided. The irregular guide groove (5025) cooperates with the irregular key (5013).

3. The large-diameter directional drilling system for coal mines underground according to claim 1, characterized in that, The outer contour surface of the irregular key (5013) is in the shape of an arc or an elliptical arc.

4. The large-diameter directional drilling system for underground coal mines according to claim 1, wherein, The radial outer side wall of the wedge-shaped claw (5023) is an inclined surface.

5. The large-diameter directional drilling system for underground coal mines according to claim 1, characterized in that, The limit joint (503) includes a third cylinder (5033). A limit convex ring (5032) is provided in the middle of the outer wall of the third cylinder (5033), and external threads (5031) are provided on the outer walls at both ends of the third cylinder (5033).

6. A method for forming a large-diameter directional long borehole in a coal mine underground, characterized in that, This method uses the coal mine underground large-diameter directional hole drilling system described in any one of claims 1 to 5, and specifically includes the following steps: Step 1, opening a hole and lowering a pipe: Use a rotary drilling method to open a hole to obtain a drilled hole in the opening section. Lower a sealing pipe (14) into the drilled hole in the opening section, and inject an expansive concrete slurry between the outer wall of the sealing pipe (14) and the hole wall of the drilled hole in the opening section to form a sealing body (15); Lower the coal mine underground large-diameter directional hole drilling system into the sealing pipe (14) and perform tool face correction; A drilled hole annulus inner section (26) is formed between the coal mine underground large-diameter directional hole drilling system and the hole wall of the to-be-formed directional hole; Step 3, add a double-wall drill pipe (6) to the sealing crossover short joint (5) in the coal mine underground large-diameter directional hole drilling system, install a hole mouth device (9) on the sealing pipe (14), and install a double-channel water injection and slag discharge device (7) and a control drilling execution device (8) on the double-wall drill pipe (6) passing through the hole mouth device (9); The liquid injection port (902) of the hole mouth device (9) is connected to an external liquid injection pump (11) through a liquid injection pipe (18); a control valve (16) is installed on the liquid outlet (901) of the hole mouth device (9), and a return liquid pipe (17) is connected to the control valve (16). The annulus channel (23) of the double-wall drill pipe (6) is a high-pressure water flow channel, and the flow direction is from the hole mouth to the hole bottom; The central channel (24) of the double-wall drill pipe (6) is a reverse flow channel, and the flow direction is from the hole bottom to the hole mouth; The space between the double-wall drill pipe (6) and the hole wall is a drilled hole annulus outer section (25), and the drilled hole annulus outer section (25) is internally connected to the hole mouth device (9); the drilled hole annulus outer section (25) is a protection hole liquid filling and intermittent flow channel, and the flow direction is from the hole mouth to the hole bottom. The interior of the water inlet passage (701) of the dual-channel water injection and slag discharge device (7) is communicated with the annulus passage (23) of the double-wall drill pipe (6). A high-pressure water pipe (19) is connected to the outside of the water inlet passage (701), and the end of the high-pressure water pipe (19) is connected to a mud pump (10); the interior of the return passage (702) of the dual-channel water injection and slag discharge device (7) is communicated with the central passage (24) of the double-wall drill pipe (6). A return water pipe (20) is connected to the outside of the return passage (702), and the end of the return water pipe (20) is connected to an external gas-liquid separation device (12); Step Four: Start the liquid injection pump (11). The liquid injection pump (11) injects hole protection fluid into the outer section (25) of the drilling annulus. After filling, adjust the liquid injection speed and feedback pressure; start the mud pump (10). The mud pump (10) injects high-pressure water into the annulus passage (23) of the double-wall drill pipe (6). The high-pressure water reaches the bottom of the hole to drive the single-bend screw motor (2) to do work, and then returns through the central passage (24) of the double-wall drill pipe (6); Step Five: Directional drilling: Control the drilling execution device (8) to drive the downhole drill string assembly to feed and rotate, and implement the compound directional drilling process. During drilling, the sliding sector wing plate (5022) on the sealing crossover sub (5) slides along the axial direction of the borehole towards the direction close to the fixed sector wing plate (5012) until the fixed sector wing plate (5012) and the sliding sector wing plate (5022) are in contact, closing the outer axial passage. The outer section (25) of the drilling annulus and the inner section (26) of the drilling annulus are separated. The outer section (25) of the drilling annulus is filled with hole protection fluid, and the inner section (26) of the drilling annulus conducts circulating slag discharge. The multiphase fluid returning through the central passage (24) of the double-wall drill pipe (6) enters the gas-liquid separation device (12) through the rubber hose (20). The gas enters the negative pressure pipe (22), and the drill cuttings enter the sewage tank (13) with water through the slag discharge pipe (21); Step Six: End-hole and withdraw the drill: When the construction reaches the designed depth, a large-diameter directional hole is obtained, and the double-wall drill pipe (6) and the underground coal mine large-diameter directional hole drilling system are withdrawn in sequence; Step Seven: Lower the pipe and connect for pumping: Lower the hole protection pipe into the large-diameter directional hole, remove the hole mouth device (9), and connect the negative pressure drainage pipeline to the sealing pipe (14) for gas drainage.

7. The hole forming method for large-diameter directional long boreholes in underground coal mines according to claim 6, characterized in that Between Step Five and Step Six, it also includes: performing external circulation flushing for auxiliary slag discharge at intervals of 100m to 150m. Specifically: Lift the underground coal mine large-diameter directional hole drilling system 2m to 5m away from the bottom of the hole, so that the fixed sector wing plate (5012) and the sliding sector wing plate (5022) on the sealing crossover sub (5) are disengaged, and the outer axial passage is opened. Stop the water supply of the mud pump (10), adjust the displacement of the liquid injection pump (11) to about 200L / min, close the control valve (16) on the hole mouth device (9), and the hole protection fluid flows from the hole mouth to the bottom of the hole in the outer section (25) of the drilling annulus, carrying the sediment and entering the central passage (24) of the drill pipe through the inclined hole passage (5016) at the sealing crossover sub (5) and returning.

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