Hole protection structure and hole protection method for directional drilling

Abstract

The invention relates to the technical field of hole protection, in particular to a hole protection structure and method for directional drilling, the hole protection structure comprises a first-stage hole protection pipe and a second-stage hole protection pipe, and the bottom of the first-stage hole protection pipe and the bottom of the second-stage hole protection pipe are provided with a first hanging drill bit and a second hanging drill bit respectively; the first-stage hole protection pipe is arranged in a main hole of a drill hole through a first hanging drill bit, through holes are formed in the positions, corresponding to branch holes of the drill hole, of the inner wall of the first-stage hole protection pipe, the second-stage hole protection pipes are continuous screen pipes, all the sections of the second-stage hole protection pipes are connected in an inserted mode, and the second-stage hole protection pipes are arranged in the branch holes through second hanging drill bits. The secondary hole protection pipes which are sequentially arranged along the through hole and are positioned outside the branch holes can be separated from the secondary hole protection pipes retained in the branch holes under the action of external force, so that the secondary hole protection pipes do not need to be fed one by one, the working efficiency is improved, continuous hole protection is realized, the smoothness of a gas flow path is ensured, the extraction effect is ensured, and the production cost is reduced. And the corner gas over-limit on the working face is prevented.

Description

Technical Field

[0001] The invention relates to the technical field of hole protection, and in particular to a hole protection structure and a hole protection method for directional drilling. Background Art

[0002] The gas geological structure of coal mines in my country is complex, with a large proportion of broken and soft coal seams and a generally high gas content (it is not easy to drill holes along the coal seams). At the same time, the collapse of broken and soft coal seams is also one of the main factors limiting gas extraction.

[0003] At present, the comb-shaped directional drilling technology is mainly used to prevent and control soft and strong coal seams. The comb-shaped directional drilling technology refers to the construction of a group of upward or downward branch holes in the main hole at a certain interval toward the target layer. The main hole is generally arranged in the layer with good porosity in the top and bottom plates of the coal seam. The branch holes enter the target coal seam according to the design requirements to achieve long-distance gas outburst elimination, pre-extraction and pressure relief extraction of broken and soft coal seams. The measure to prevent and control borehole collapse is mainly to send screen pipes into the gas extraction holes, which have the function of resisting borehole collapse and extracting gas through the screen holes. However, it is usually necessary to gradually send the screen pipes one by one, and continuous hole protection cannot be achieved. In addition, high-pressure water is used to impact the screen pipes to make them fall off, which is easy to accumulate water in the borehole and cause the borehole to fail, especially in the downward branch holes constructed around the main hole. Since the borehole is inclined downward, coal powder and sewage will accumulate in the downward branch holes during and after the drilling construction process. The borehole is long, and it is difficult to discharge coal powder and sewage out of the borehole using conventional compressed air measures, which seriously restricts the extraction effect of the borehole. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a hole protection structure and a hole protection method for directional drilling which can continuously protect the hole and ensure the drilling effect.

[0005] A first aspect of the present invention provides a hole protection structure for a main hole and a branch hole of a directional drilling, comprising a primary hole protection pipe and a secondary hole protection pipe, wherein the primary hole protection pipe is arranged in the main hole of the drilling hole, and a through hole is opened on the inner wall of the primary hole protection pipe at a position corresponding to the branch hole of the drilling hole, the secondary hole protection pipe is a continuous screen pipe, and each section of the secondary hole protection pipe is plug-connected, the secondary hole protection pipe is arranged in the branch hole, and is arranged in sequence along the through hole, and the secondary hole protection pipe located outside the branch hole can be separated from the secondary hole protection pipe retained in the branch hole under the action of external force.

[0006] Optionally, a first suspension drill bit and a second suspension drill bit are respectively provided at the bottom of the primary hole protection tube and the secondary hole protection tube, and a clamping ring is provided at the outer periphery of the first suspension drill bit and the second suspension drill bit, and the clamping ring and the first suspension drill bit and the second suspension drill bit are connected by a spring;

[0007] When the clamping ring is not acted upon by an external force, the clamping ring is spread out in all directions; when the clamping ring is acted upon by an external force, the clamping ring is closed toward the inner side of the first suspension drill bit or the second suspension drill bit.

[0008] Optionally, the diameter of the primary hole protection tube is 60 to 70 mm, and the diameter of the secondary hole protection tube is 30 to 50 mm.

[0009] Optionally, the length of the secondary hole protection tube retained in the branch hole is 300 to 500 mm greater than the length of the branch hole, and the secondary hole protection tube retained in the branch hole is partially overlapped with the primary hole protection tube.

[0010] Optionally, a gauze is provided at one end of the secondary hole protection tube close to the bottom of the branch hole.

[0011] Optionally, the secondary hole protection tubes are sequentially lowered into the branch holes from far to near along the extension direction of the primary hole protection tube.

[0012] A second aspect of the present invention provides a method for protecting a directional drilling hole, which is completed based on the directional drilling hole protection structure described in any of the above embodiments, and includes the following steps:

[0013] S1, constructing the main hole, and constructing a plurality of the main holes along the direction of the coal seam;

[0014] S2, constructing the branch holes, constructing a plurality of the branch holes in the circumferential direction of the main hole at intervals of 30 to 50 m;

[0015] S3, clearing the accumulated water, coal powder and coal slag in the main hole, lowering the drill bit and drill rod into the bottom of the main hole, lowering the water pump along the inside of the drill rod to the bottom of the main hole, and connecting the water pump to the water pump;

[0016] S4, clearing the accumulated water, coal powder and coal slag in the branch hole, lowering the drill bit and the drill rod into the bottom of the branch hole according to the measurement while drilling system of the directional drilling rig, lowering the water pump along the inside of the drill rod to the bottom of the branch hole, and connecting the water pump to the water pump;

[0017] S5, lowering a primary hole protection pipe, lowering the drill bit, the drill rod and the primary hole protection pipe into the main hole, and fixing the primary hole protection pipe in the main hole;

[0018] S6, lowering the secondary hole protection pipe, when the primary hole protection pipe is lowered into place, the drill bit drills into the primary hole protection pipe along the inclination and azimuth parameters of the branch hole, and at the same time, the drill rod and the secondary hole protection pipe follow the drill bit to drill the primary hole protection pipe along the direction from the end of the main hole to the opening end of the main hole, until the secondary hole protection pipe is lowered into the bottom of the branch hole;

[0019] S7, retaining the secondary hole protection tube, when the secondary hole protection tube is lowered into the bottom of the branch hole, applying external force to the secondary hole protection tube located outside the branch hole, so that the secondary hole protection tube is retained in the branch hole;

[0020] S8. After the secondary hole protection pipes are lowered into the branch holes, the main hole and the branch holes are sealed. After the holes are sealed, the primary hole protection pipes are connected to the extraction system to extract the directional drilling holes.

[0021] Optionally, the water pumping pipe is a solid pipe made of plastic material, and the diameter of the water pumping pipe is 60 to 70 mm;

[0022] The negative pressure of the water pump reaches 50 to 1000 KPa.

[0023] Optionally, the drill bit is an open-and-close drill bit, and the drill rod is a hollow drill rod;

[0024] An openable crossbeam is arranged in the middle of the drill bit. When the drill bit is inserted into the main hole or the branch hole, the crossbeam is in a closed state. When the main hole or the branch hole is subjected to thrust, the crossbeam is opened.

[0025] Compared with the prior art, the technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0026] The present embodiment provides a hole protection structure and a hole protection method for directional drilling. The hole protection structure drills a first-level hole protection pipe at the intersection of the main hole and the branch hole and inserts a second-level hole protection pipe. The second-level hole protection pipe can be retained in the branch hole by pulling with external force. There is no need to send the second-level hole protection pipes one by one, thereby improving work efficiency and achieving continuous hole protection. At the same time, the main hole and branch holes of the directional drilling are protected, and the main hole and branch holes after the protection are ensured to remain as flow channels, thereby ensuring the smooth flow path of the gas and the extraction effect. As the working face is recovered, the role of pressure relief extraction is gradually played to effectively intercept the pressure relief gas, thereby preventing the occurrence of excessive gas in the corner of the working face. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 A cross-sectional view of the hole protection structure of the main hole and the branch hole of the directional drilling according to an embodiment of the present invention;

[0030] Figure 2 It is a schematic diagram of the structure of the plug-in connection between two sections of secondary hole-protecting pipes according to an embodiment of the present invention;

[0031] Figure 3 It is a schematic diagram of the structure of the secondary hole protection pipe according to an embodiment of the present invention when it is lowered into the branch hole.

[0032] Among them, 1. primary hole protection tube; 101. through hole; 2. secondary hole protection tube; 3. main hole; 4. branch hole; 5. gauze; 6. second hanging drill bit; 7. drill bit; 8. drill rod; 9. water pump; 10. crossbeam; 11. retaining ring. DETAILED DESCRIPTION

[0033] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0035] Reference Figures 1 to 3 As shown, the first aspect of the present embodiment provides a hole protection structure for directional drilling, including a primary hole protection pipe 1 and a secondary hole protection pipe 2. The primary hole protection pipe 1 is arranged in the main hole 3 of the borehole, and a through hole 101 is opened on the inner wall of the primary hole protection pipe 1 at a position corresponding to the branch hole 4. The secondary hole protection pipe 2 is a continuous screen pipe, and each section of the secondary hole protection pipe 2 is plug-connected. The secondary hole protection pipe 2 is arranged in the branch hole 4 and arranged in sequence along the through hole 101. The secondary hole protection pipe 2 located outside the branch hole 4 can be separated from the secondary hole protection pipe 2 retained in the branch hole 4 under the action of external force.

[0036] Among them, the main hole 3 and the branch hole 4 of the directional drilling are both protected, and the first-level protection tube 1 is a screen tube made of polyethylene. The diameter of the screen hole on the first-level protection tube 1 is 5 to 8 mm. Combined with the drilling parameters of each branch hole 4 measured by the directional trajectory measuring instrument, the opening position of each branch hole 4 is marked at the corresponding position of the first-level protection tube 1, and at the same time, a through hole 101 with a diameter of 30 to 50 mm is opened along the borehole wall in the first-level protection tube 1 to facilitate the subsequent second-level protection tube 2 to be lowered from the inside of the first-level protection tube 1 and penetrate into the branch hole 4 through the through hole 101. After the second-level protection tube 2 is lowered into place, since the second-level protection tube 2 is a continuous screen tube and each section of the second-level protection tube 2 is connected by plugging, the second-level protection tube 2 is pulled by external force to be located on one side of the horizontal section. The borehole tube is separated from the borehole protection tube on the side that turns downward, so that the borehole protection tube on the side that turns downward of the secondary borehole protection tube 2 is retained in the branch hole 4. This borehole protection structure drills the primary borehole protection tube 1 at the intersection of the main bore 3 and the branch hole 4 and inserts the secondary borehole protection tube 2, and can use external force to pull the secondary borehole protection tube 2 to be retained in the branch hole 4, without the need to send the secondary borehole protection tube 2 one by one, thereby improving work efficiency and realizing continuous borehole protection. At the same time, it realizes the borehole protection of the main bore 3 and the branch hole 4 of the directional drilling, and ensures that the main bore 3 and the branch hole 4 after the borehole protection are still flow channels, ensuring the smooth flow path of the gas, ensuring the extraction effect, and gradually playing the role of pressure relief extraction as the working face is recovered, effectively intercepting the pressure relief gas, and preventing the occurrence of gas exceeding the limit in the corner of the working face.

[0037] Further, see Figure 3As shown, the bottom of the primary hole protection tube 1 and the secondary hole protection tube 2 are respectively provided with a first suspension drill bit and a second suspension drill bit 6, and the outer periphery of the first suspension drill bit and the second suspension drill bit 6 are provided with a clamping ring 11, and the clamping ring 11 and the first suspension drill bit and the second suspension drill bit 6 are connected by a spring; when the clamping ring 11 is not subjected to external force, the clamping ring 11 expands to the surroundings, and when the clamping ring 11 is subjected to external force, the clamping ring 11 closes toward the inner side of the first suspension drill bit or the second suspension drill bit 6. Specifically, when the primary hole protection tube 1 and the secondary hole protection tube 2 are respectively lowered into the main hole 3 and the branch hole 4, and the hanging drill bit connected to the hole protection tube has not yet entered the drill pipe 8, the clamping ring 11 of the hanging drill bit is in a natural state and is expanded outward. When the hanging drill bit and the hole protection tube are sent into the drill pipe 8, the clamping ring 11 is closed toward the inside of the hanging drill bit due to the resistance of the inner wall of the drill pipe 8 to push the drill bit 7 away, thereby driving the primary hole protection tube 1 and the secondary hole protection tube 2 to be lowered into the main hole 3 and the branch hole 4 respectively. When the first hanging drill bit and the second hanging drill bit 6 reach the bottom of the main hole 3 and the branch hole 4 respectively with the primary hole protection tube 1 and the secondary hole protection tube 2, the inner diameter of the main hole 3 and the branch hole 4 is larger than the diameter of the first hanging drill bit and the second hanging drill bit 6, so that the clamping rings 11 of the first hanging drill bit and the second hanging drill bit 6 are no longer affected by external forces and are both expanded to the surroundings, thereby fixing the primary hole protection tube 1 and the secondary hole protection tube 2 in the main hole 3 and the branch hole 4 respectively.

[0038] Furthermore, in order to ensure that the secondary hole protection tube 2 can enter the branch hole 4 through the primary hole protection tube 1, the diameter of the primary hole protection tube 1 is 60 to 70 mm, and the diameter of the secondary hole protection tube 2 is 30 to 50 mm.

[0039] In some embodiments, the length of the secondary hole protection tube 2 retained in the branch hole 4 is greater than the length of the branch hole 4 by 300 to 500 mm, and the secondary hole protection tube 2 retained in the branch hole 4 partially overlaps with the primary hole protection tube 1. Specifically, by setting the length of the secondary hole protection tube 2 greater than the length of the branch hole 4, there is an overlap section between the secondary hole protection tube 2 retained in the branch hole 4 and the primary hole protection tube 1. By setting the overlap section of the secondary hole protection tube 2, it is avoided that the secondary hole protection tube 2 is misaligned when it is lowered or pulled, and the secondary hole protection tube 2 is disconnected to form a hole protection gap. The junction between the main hole 3 and the branch hole 4 is a location where stress is concentrated and distributed. The secondary hole protection tube 2 is overlapped with the primary hole protection tube 1 at this location, which improves the support strength of this location. At the same time, before lowering the secondary hole protection tube 2, the length of the branch hole 4 needs to be measured first. By setting the overlap section, it is ensured that the length of the secondary hole protection tube 2 is greater than the length of the branch hole 4, and it is avoided that the error in measurement causes a hole protection vacuum between the main hole 3 and the branch hole 4.

[0040] Reference Figure 2As shown, a gauze 5 is provided at one end of the secondary hole protection tube 2 near the bottom of the branch hole 4. Specifically, the branch hole 4 provided in this embodiment is a downward branch hole, that is, the secondary hole protection tube 2 is constructed downward. During the construction process, water accumulation, coal slag and coal powder accumulation will appear at the bottom of the borehole. During extraction, coal particles are easily sucked into the secondary hole protection tube 2, causing the borehole to be blocked. By setting the gauze 5, the blockage of the borehole caused by the adsorption of coal particles by the borehole is avoided.

[0041] In other embodiments, the secondary hole protection tube 2 is sequentially lowered into the branch hole 4 from far to near along the extension direction of the primary hole protection tube 1. Specifically, the secondary hole protection tube 2 enters the primary hole protection tube 1, and is lowered into the branch hole 4 backward along the end of the primary hole protection tube 1 toward the direction of the entry end. After each secondary hole protection tube 2 is lowered, the secondary hole protection tube 2 is promptly pulled by external force to be retained in the branch hole 4, and the secondary hole protection tubes 2 do not need to be sent in one by one, thereby improving work efficiency.

[0042] A second aspect of the present embodiment provides a hole protection method for directional drilling, which is completed based on the above-mentioned hole protection structure for directional drilling, and includes the following steps:

[0043] S1, construct main hole 3, construct multiple main holes 3 along the coal seam;

[0044] S2, construct branch holes 4, construct multiple branch holes 4 in the circumferential direction of the main hole 3 at intervals of 30 to 50 m;

[0045] The main hole 3 and branch holes 4 constructed above are constructed according to conventional drilling procedures. The main hole 3 with a length ranging from 300 to 600m is constructed along the direction of the coal seam. During the drilling process, branch holes 4 are constructed around the main hole 3 every 30 to 50m. The holes drilled toward the upper part of the borehole are upward branch holes, and the holes drilled toward the lower part of the borehole are downward branch holes.

[0046] Since the end point of the upward branch hole is higher than the main hole 3, the accumulated water, coal powder and coal slag in the borehole will accumulate towards the main hole 3 under the action of gravity. Since the end point of the downward branch hole is lower than the main hole 3, a large amount of water, coal powder and coal slag will accumulate in the borehole. Therefore, the main hole 3 and the downward branch hole need to be cleared of accumulated water, coal powder and coal slag.

[0047] S3, clear the accumulated water, coal powder and coal slag in the main hole 3, lower the drill bit 7 and the drill rod 8 into the bottom of the main hole 3, lower the water pump along the inside of the drill rod 8 to the bottom of the main hole 3, and connect the water pump to the water pump 9;

[0048] S4, clear the accumulated water, coal powder and coal slag in the branch hole 4, according to the drilling measurement system of the directional drilling rig, lower the drill bit 7 and the drill rod 8 into the bottom of the branch hole 4, lower the water pump along the inside of the drill rod 8 to the bottom of the branch hole 4, and connect the water pump to the pump 9;

[0049] The accumulated water, coal powder and coal slag in the borehole should be removed after the construction of the main hole 3 and the branch hole 4 is completed, that is, the drill rod and drill bit used for normal drilling are withdrawn, and then the drill bit 7, drill rod 8 and pumping pipe used for cleaning are sent into the main hole 3 and the branch hole 4.

[0050] The diameter of the drill bit 7 is 95 to 113 mm, the diameter of the drill rod 8 is 75 to 80 mm, the length of each section of the drill rod 8 is 2 m, and they are connected by threaded connections.

[0051] Among them, the drill bit 7 is an open and close drill bit, and the drill rod 8 is a hollow drill rod, which is different from the drill bits and drill rods used for constructing the main hole 3 and branch hole 4 mentioned above. An open and close crossbeam 10 is arranged in the middle of the drill bit 7. When the drill bit 7 is sent into the main hole 3 or the branch hole 4, the crossbeam 10 is in a closed state. When the main hole 3 or the branch hole 4 is subjected to thrust, the crossbeam 10 opens, that is, when the primary hole protection tube 1 or the secondary hole protection tube 2 connected by the first suspended drill bit and the second suspended drill bit 6 is lowered into the borehole, the suspended drill bit can push open the crossbeam 10 of the drill bit 7, thereby realizing the lowering of the suspended drill bit and the hole protection tube into the borehole.

[0052] Furthermore, the water pumping pipe is a solid tube made of plastic, that is, there are no sieve holes on the inner wall of the water pumping pipe, the diameter of the water pumping pipe is 60 to 70 mm, and the water pumping pipe can be lowered into the bottom of the borehole from the hollow part of the drill rod 8. When the drill rod 8 is lowered into the bottom of the borehole, the water pumping pipe is connected to the water pump 9. The negative pressure of the water pump 9 must reach 50 to 1000 KPa, which can realize the discharge of all the coal powder, coal slag and water in the borehole.

[0053] S5. Lower the primary hole protection tube 1, lower the drill bit 7, drill rod 8 and primary hole protection tube 1 into the main hole 3, and according to the set opening positions of each branch hole 4, align the through hole 101 set on the primary hole protection tube 1 with the opening positions of the branch holes 4. Then, the retaining ring of the first hanging drill bit is closed toward the inside of the first hanging drill bit under the action of the resistance of the inner wall of the drill rod 8 to push the drill bit 7 away, thereby driving the primary hole protection tube 1 to enter the main hole 3. When the first hanging drill bit reaches the bottom of the main hole 3 with the primary hole protection tube 1, the inner diameter of the main hole 3 is larger than the diameter of the first hanging drill bit, so that the retaining ring of the first hanging drill bit is no longer affected by external force and expands to the surroundings, thereby fixing the primary hole protection tube 1 in the main hole 3;

[0054] S6. Lower the secondary hole protection pipe 2. When the primary hole protection pipe 1 is lowered into place, the drill bit 7 drills into the primary hole protection pipe 1 along the inclination and azimuth parameters of the branch hole 4. At the same time, the drill rod 8 and the secondary hole protection pipe 2 follow the drill bit 7 to drill the primary hole protection pipe 1 along the end of the main hole 3 to the opening end of the main hole 3. The drill bit 7 has a guiding effect. When the drill bit 7 reaches the junction of the main hole 3 and the branch hole 4, it can enter the branch hole 4 through the through hole 101 set on the primary hole protection pipe 1, and the second hanging drill bit 6 is lowered into the drill rod 8. and the secondary hole protection tube 2, the retaining ring of the second suspension drill bit 6 is closed toward the inside of the second suspension drill bit 6 by the resistance of the inner wall of the drill pipe 8, so as to push the drill bit 7, thereby driving the secondary hole protection tube 2 to go down into the branch hole 4. When the second suspension drill bit 6 reaches the bottom of the branch hole 4 with the secondary hole protection tube 2, the inner diameter of the branch hole 4 is larger than the diameter of the second suspension drill bit 6, so that the retaining ring of the second suspension drill bit 6 is no longer affected by external force and expands to the surroundings, thereby realizing the secondary hole protection tube 2 going down into the bottom of the branch hole 4;

[0055] S7, retain the secondary hole protection pipe 2, the secondary hole protection pipe 2 is a continuous screen pipe, on the basis of accurately calculating the length of each section of the secondary hole protection pipe 2, each section of the secondary hole protection pipe 2 and the continuous secondary hole protection pipe 2 are connected by plugging, when the secondary hole protection pipe 2 is lowered into the bottom of the branch hole 4, an external force is applied to the secondary hole protection pipe outside the branch hole 4, due to the angle between the branch hole 4 and the main hole 3, there is friction and resistance between the primary hole protection pipe 1 and the secondary hole protection pipe 2, and the friction resistance at the connection between the pipelines is greater than 300N, so that the secondary hole protection pipe outside the branch hole 4 is separated from the secondary hole protection pipe inside the branch hole 4, that is, the continuous screen pipe is separated from the secondary hole protection pipe 2;

[0056] The branch hole 4 for performing the cleaning operation and hole protection is a downward branch hole.

[0057] S8. After the secondary borehole protection pipes 2 are lowered into the branch holes 4, the main hole 3 and the branch holes 4 are sealed using the traditional "two blocking and one injection" sealing method. After sealing, the primary borehole protection pipes 1 are connected to the extraction system to extract the entire directional drilling hole.

[0058] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0059] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments described herein, but should conform to the widest scope consistent with the principles and novel features invented herein.

Claims

1. A hole protection structure for directional drilling, characterized in that: The invention comprises a primary hole protection pipe (1) and a secondary hole protection pipe (2), wherein the primary hole protection pipe (1) is arranged in the main hole (3) of the borehole, and a through hole (101) is provided on the inner wall of the primary hole protection pipe (1) at a position corresponding to the branch hole (4) of the borehole, the secondary hole protection pipe (2) is a continuous screen pipe, and each section of the secondary hole protection pipe (2) is plug-connected, the secondary hole protection pipe (2) is arranged in the branch hole (4), and is arranged in sequence along the through hole (101), and the secondary hole protection pipe (2) located outside the branch hole (4) can be separated from the secondary hole protection pipe (2) retained in the branch hole (4) under the action of external force.

2. The hole protection structure for directional drilling according to claim 1, characterized in that: A first suspension drill bit and a second suspension drill bit (6) are respectively arranged at the bottom of the primary hole protection tube (1) and the secondary hole protection tube (2); a clamping ring (11) is arranged on the outer periphery of the first suspension drill bit and the second suspension drill bit (6); and the clamping ring (11) and the first suspension drill bit and the second suspension drill bit (6) are connected via a spring; When the clamping ring (11) is not acted upon by an external force, the clamping ring (11) spreads out in all directions; when the clamping ring (11) is acted upon by an external force, the clamping ring (11) closes toward the inner side of the first suspension drill bit or the second suspension drill bit (6).

3. The hole protection structure for directional drilling according to claim 1, characterized in that: The diameter of the primary hole protection tube (1) is 60 to 70 mm, and the diameter of the secondary hole protection tube (2) is 30 to 50 mm.

4. The hole protection structure for directional drilling according to claim 1, characterized in that: The length of the secondary hole protection tube (2) retained in the branch hole (4) is 300 to 500 mm greater than the length of the branch hole (4), and the secondary hole protection tube (2) retained in the branch hole (4) is partially overlapped with the primary hole protection tube (1).

5. The hole protection structure for directional drilling according to claim 1, characterized in that: A gauze net (5) is provided at one end of the secondary hole protection tube (2) close to the bottom of the branch hole (4).

6. The hole protection structure for directional drilling according to claim 1, characterized in that: The secondary hole protection pipe (2) is sequentially lowered into the branch holes (4) from far to near along the extension direction of the primary hole protection pipe (1).

7. A method for protecting a directional drilling hole, based on the directional drilling hole protection structure according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, constructing the main hole (3), constructing a plurality of the main holes (3) along the direction of the coal seam; S2, constructing the branch holes (4), constructing a plurality of the branch holes (4) at intervals of 30 to 50 m in the circumferential direction of the main hole (3); S3, clearing the accumulated water, coal powder and coal slag in the main hole (3), lowering the drill bit (7) and the drill rod (8) to the bottom of the main hole (3), lowering the water extraction pipe along the inside of the drill rod (8) to the bottom of the main hole (3), and connecting the water extraction pipe to the water pump (9); S4, clearing the accumulated water, coal powder and coal slag in the branch hole (4), lowering the drill bit (7) and the drill rod (8) to the bottom of the branch hole (4) according to the measurement while drilling system of the directional drilling rig, lowering the water pumping pipe along the inside of the drill rod (8) to the bottom of the branch hole (4), and connecting the water pumping pipe to the water pump (9); S5, lowering the primary hole protection pipe (1), lowering the drill bit (7), the drill rod (8) and the primary hole protection pipe (1) into the main hole (3), and arranging the primary hole protection pipe (1) in the main hole (3); S6, lowering the secondary bore protection pipe (2). When the primary bore protection pipe (1) is lowered into place, the drill bit (7) drills into the primary bore protection pipe (1) along the inclination and azimuth parameters of the branch hole (4). At the same time, the drill rod (8) and the secondary bore protection pipe (2) follow the drill bit (7) to drill the primary bore protection pipe (1) along the direction from the end of the main hole (3) to the opening end of the main hole (3), until the secondary bore protection pipe (2) is lowered into the bottom of the branch hole (4); S7, retaining the secondary hole protection tube (2), when the secondary hole protection tube (2) is lowered into the bottom of the branch hole (4), applying external force to the secondary hole protection tube located outside the branch hole (4), so that the secondary hole protection tube (2) is retained in the branch hole (4); S8. After the secondary hole protection pipes (2) are lowered into the branch holes (4), the main hole (3) and the branch holes (4) are sealed. After the holes are sealed, the primary hole protection pipes (1) are connected to the extraction system to extract the directional drilling holes.

8. The method for protecting a directional drilling hole according to claim 7, characterized in that: The water pumping pipe is a solid pipe made of plastic material, and the diameter of the water pumping pipe is 60 to 70 mm; The negative pressure of the water pump (9) reaches 50 to 1000 KPa.

9. The method for protecting a directional drilling hole according to claim 7, characterized in that: The drill bit (7) is an open-close drill bit, and the drill rod (8) is a hollow drill rod; An openable cross beam (10) is provided in the middle of the drill bit (7). When the drill bit (7) is inserted into the main hole (3) or the branch hole (4), the cross beam (10) is in a closed state. When the main hole (3) or the branch hole (4) is subjected to a thrust force, the cross beam (10) is opened.

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