Unfoldable reverse drilling device and reverse drilling mining method

Abstract

The invention discloses an expandable reverse drilling device and a reverse drilling mining method, and belongs to the technical field of oil and gas drilling, oil and gas exploitation and mining. The expandable reverse drilling device comprises an upper connector, a tool arm, a tool assembly, a flexible wear-resistant waterproof baffle, a sliding rod, a transverse supporting rod, an inclined supporting rod, an upper sliding block, a lower sliding block, a strong spring, a locking mechanism, a guide head and the like. According to the reverse drilling mining method, reverse drilling is conducted on a guide well drilled in advance through the expandable reverse drilling device. Crushed mineral particles are carried to the ground by drilling fluid, solid mineral fluidization exploitation is achieved, and the method is suitable for exploitation of relatively loose underground resources such as oil sand, thickened oil, natural gas hydrates and deep coal; a large-diameter goaf is formed underground, and the large-diameter goaf is backfilled in time; mineral mining in the large-diameter goaf is completed after reverse drilling is completed, the single-well mining period of an oil and gas well is shortened to several days from several years, the mining cost is low, and the return on investment is ultra-fast.

Description

Technical Field

[0001] The present invention relates to the technical fields of oil and gas drilling, oil and gas production, and mining, and specifically, to a deployable reverse drill and a reverse drilling mining method. Background Art

[0002] The global oil sand and heavy oil resources are extremely rich. The traditional thermal recovery technology has a long production cycle, high production cost, and poor production efficiency. The global natural gas hydrate resources are abundant, but due to the lack of safe, efficient, and economic production technologies, commercial production has not been achieved yet. Due to safety considerations, the deep coal resources buried more than 1000 meters in China have hardly been exploited so far, and the exploitation potential is huge. To safely, efficiently, and economically exploit relatively loose underground resources such as oil sand, heavy oil, natural gas hydrate, and deep coal, it is urgent to develop disruptive production technologies. Summary of the Invention

[0003] In order to safely, efficiently, and economically exploit relatively loose underground resources such as oil sand, heavy oil, natural gas hydrate, and deep coal, the present invention provides a deployable reverse drill and a reverse drilling mining method. The deployable reverse drill has a simple and reliable structure. The reverse drilling mining method uses the deployable reverse drill to reverse drill a pilot well to form a large-diameter wellbore (goaf), and timely backfill the goaf. Completing the reverse drilling means completing the mineral exploitation in the large-diameter wellbore, with high exploitation efficiency, low exploitation cost, and extremely fast return on investment.

[0004] The technical solution adopted by the embodiments of the present invention to solve its technical problems is:

[0005] A deployable reverse drill includes an upper sub, cutter arms, a cutter assembly, a sliding rod, a horizontal support rod, an inclined support rod, an upper slider, a lower slider, and a strong spring; the upper sub is fixed at the upper end of the sliding rod; the cutter arms are in a strip structure; the cutter assembly is installed on the cutter arms; the upper ends of the cutter arms are hinged to the upper sub; both the upper slider and the lower slider are sleeved outside the sliding rod; one end of the horizontal support rod is hinged to the middle of the cutter arm, and the other end of the horizontal support rod is hinged to the upper slider; one end of the inclined support rod is hinged to the middle of the horizontal support rod, and the other end of the inclined support rod is hinged to the lower slider; an external locking mechanism is arranged inside the lower slider; the strong spring pushes the upper slider and the lower slider to slide upward; when the lower slider is in the lower locking position, the external locking mechanism locks the lower slider and keeps the cutter arms in a retracted state; when the lower slider is in the upper locking position, the external locking mechanism locks the lower slider and keeps the cutter arms in an unfolded state.

[0006] A reverse drilling mining method uses the above-mentioned deployable reverse drill to reverse drill a pilot well to form a large-diameter wellbore (goaf), and timely backfill the goaf. The operation steps are generally as follows:

[0007] Step 1: Drill a pilot well using conventional drilling technology;

[0008] Step 2: Lower the expandable underreamer to the bottom of the pilot well. During this process, the cutter arms of the expandable underreamer are in the retracted state.

[0009] Step 3: Drop the down unlocker to unlock it.

[0010] Step 4: Create a cavity to fully expand and lock the cutter arms of the expandable underreamer.

[0011] Step 5: Reverse drill. The drilling fluid carries the crushed mineral particles into the annulus of the pilot well and flows to the surface.

[0012] Step 6: Drop the up unlocker to release the expanded state of the cutter arms of the expandable underreamer.

[0013] Step 7: Pull out the expandable underreamer.

[0014] Step 8: Abandon the well with cement.

[0015] The beneficial effects of the embodiments of the present invention are as follows:

[0016] 1. Provide a subversive mining method for difficult-to-produce mineral resources. Its subversiveness is mainly manifested in: breaking through the application depth limit of traditional mining methods, being able to mine oil sands deeper than 75 meters and coal deeper than 1000 meters; subverting the traditional drilling direction; subverting underground in-situ mining including SAGD; making the oil production process change from "invisible and intangible" to "visible and tangible"; subverting the traditional coal mining method and realizing fully underground non-polluting mining.

[0017] 2. Safe and environmentally friendly mining. Backfill in a timely manner, there is no solid waste on the ground, and it avoids the collapse of the mined-out area and ground subsidence.

[0018] 3. The single-well mining cycle is extremely short. Completing the reverse drilling means completing the mining of minerals in the large-diameter mined-out area. The single-well mining period of oil and gas wells is shortened from several years to several days, and the investment return is extremely fast.

[0019] 4. High recovery rate. Intensively arrange wells and implement three-dimensional development to "extract" as many minerals as possible, and the recovery rate is expected to reach more than 40%.

[0020] 5. Low single-well mining cost. Completing the reverse drilling means completing the mining of minerals in the large-diameter mined-out area, which can save operations such as running technical casing and liner, cementing, logging, perforating, steam injection or electric heating, and pumping oil, saving related costs and operation time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings constituting the specification of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0022] Figure 1 This is a schematic structural view of the expandable backreamer of the present invention in a retracted state.

[0023] Figure 2 This is a schematic structural view of the expandable backreamer of the present invention in an expanded state.

[0024] Figure 3 This is a schematic structural view of the flexible wear-resistant and waterproof baffle.

[0025] Figure 4 This is a schematic structural view of the slide bar and the locking mechanism.

[0026] Figure 5 This is a schematic structural view of the lower slider and the locking mechanism.

[0027] Figure 6 This is a schematic structural view of the upper slider and the slide bar.

[0028] Figure 7 This is a schematic view of the lower unlocker.

[0029] Figure 8 This is a schematic view of the upper unlocker.

[0030] Figure 9 This is a schematic view of the lower unlocker passing through the first locking mechanism.

[0031] Figure 10 This is a schematic view of the lower unlocker placed in the guide head.

[0032] Figure 11 This is a schematic view of the upper unlocker located at the second locking mechanism.

[0033] Figure 12 This is a schematic view of the backreaming mining method of the present invention for timely backfilling the mined-out area.

[0034] The description of the reference numerals is as follows:

[0035] 1. Upper sub; 2. Cutter arm; 3. Cutter assembly; 4. Slide bar; 5. Limit block; 6. Horizontal support bar; 7. Oblique support bar; 8. Upper slider; 9. Lower slider; 10. Strong spring; 11. Slide rail; 12. Guide head; 13. Flexible wear-resistant and waterproof baffle; 14. First locking mechanism; 15. Second locking mechanism; 17. Outer locking mechanism; 18. Lower unlocker; 19. Upper unlocker; 20. Guide shaft; 21. Mined-out area; 22. Backfill material;

[0036] 1201. Nozzle;

[0037] 1701. Outer lock pin; 1702. Outer spring;

[0038] 1401. First mounting through-hole; 1402. First locking pin; 1403. First spring;

[0039] 1501. Second mounting through-hole; 1502. Second locking pin; 1503. Second spring. Specific embodiments

[0040] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0041] As Figures 1 to 6 shown, a deployable backreamer according to an embodiment of the present invention includes an upper sub 1, cutter arms 2, a cutter assembly 3, a sliding rod 4, a limit block 5, a horizontal support rod 6, an inclined support rod 7, an upper sliding block 8, a lower sliding block 9, and a strong spring 10; the upper sub 1 is fixed to the upper end of the sliding rod 4 and is connected to the drill string by threads, and also serves as a stabilizer for the bottom hole assembly; the deployable backreamer is equipped with multiple cutter arms 2, and the upper ends of the cutter arms 2 are hinged to the upper sub 1; the cutter assembly 3 is installed on the cutter arms 2, and multiple cutter assemblies 3 are installed on each cutter arm 2. The cutter assembly 3 is mainly composed of a cutter and a bearing, and is used for breaking the mineral reservoir; the limit block 5 can limit the upper limit position of the upward sliding of the upper sliding block 8; both the upper sliding block 8 and the lower sliding block 9 are sleeved outside the sliding rod 4, the upper sliding block 8 and the lower sliding block 9 are arranged at intervals up and down, and both the upper sliding block 8 and the lower sliding block 9 can slide up and down; one end of the horizontal support rod 6 is hinged to the middle of the cutter arm 2, and the other end of the horizontal support rod 6 is hinged to the upper sliding block 8; one end of the inclined support rod 7 is hinged to the middle of the horizontal support rod 6, and the other end of the inclined support rod 7 is hinged to the lower sliding block 9; an external locking mechanism 17 is arranged in the lower sliding block 9; the strong spring 10 pushes the upper sliding block 8 and the lower sliding block 9 to slide upward; when the lower sliding block 9 is in the lower locking position, the cutter arms 2 are in the retracted state, and the external locking mechanism 17 in the lower sliding block 9 locks the lower sliding block 9 in the lower locking position, completing the locking of the lower sliding block 9 below and keeping the cutter arms 2 in the retracted state; when the lower sliding block 9 slides upward to the limit block 5, the cutter arms 2 are fully deployed, and the external locking mechanism 17 in the lower sliding block 9 simultaneously slides upward to the upper locking position, and the external locking mechanism 17 locks the lower sliding block 9 in the upper locking position, completing the locking of the lower sliding block 9 above and keeping the cutter arms 2 in the deployed state.

[0042] As Figures 1 to 2 shown, the cutter assembly 3 includes cutting teeth, and these cutting teeth can be PDC cutting teeth, cemented carbide teeth, or milling teeth or other types of cutting teeth. The cutter assembly 3 installed at the lower end of the cutter arm 2 includes cutters for creating a cavity and maintaining the gauge. There are two installation methods for the cutter assembly 3: one is straddling on the cutter arm 2, and the other is sleeving on the cutter arm 2.

[0043] As Figure 3As shown, a flexible wear-resistant and waterproof baffle 13 is connected between two adjacent cutter arms 2. The flexible wear-resistant and waterproof baffle 13 is in a fan-shaped structure, foldable, and can be unfolded as the cutter arm 2 unfolds and can also be folded up as the cutter arm 2 folds in. After the flexible wear-resistant and waterproof baffle 13 is fully unfolded, it can prevent the broken mineral particles from entering the large-diameter goaf, allowing them to enter the annular space of the pilot well 20 with the drilling fluid and be carried to the ground by the drilling fluid. After the cutter arm 2 is fully unfolded, the horizontal support rod 6 and the inclined support rod 7 support the cutter arm 2, enabling the cutter arm 2 to withstand a certain drilling pressure (the upward pulling force of the drill string).

[0044] As Figures 1 to 6 shown, the expandable backdrill also includes a slide rail 11 and a guide head 12. Two slide rails 11 are symmetrically machined on the outer side of the slide rod 4 below the limit block 5. The slide rails 11 are engaged with the inner chutes of the upper slider 8 and the lower slider 9, forcing the upper slider 8 and the lower slider 9 to slide axially only along the slide rod 4 to achieve the expansion and folding of the expandable backdrill. The guide head 12 is threadedly connected to the lower end of the slide rod 4 and is used to guide the expandable backdrill to the bottom of the pre-drilled pilot well 20. The guide head 12 is equipped with a plurality of nozzles 1201, and the nozzles 1201 are communicated with the internal channel of the slide rod 4.

[0045] As Figure 1 and Figure 2 shown, a strong spring 10 is sleeved outside the slide rod 4 and is located between the upper slider 8 and the lower slider 9; when the cutter arm 2 is folded in, the strong spring 10 is in a strongly compressed state; after the cutter arm 2 is fully unfolded, the strong spring 10 is in a weakly compressed state.

[0046] As Figure 5 and Figure 6 shown, both the upper slider 8 and the lower slider 9 are in an annular structure, and an external locking mechanism 17 is arranged inside the lower slider 9. The external locking mechanism 17 includes an external lock pin 1701 and an external spring 1702, and the external spring 1702 tends to push the external lock pin 1701 towards the slide rod 4.

[0047] As Figures 1 to 6 shown, a first locking mechanism 14 and a second locking mechanism 15 are arranged inside the side wall of the slide rod 4. The first locking mechanism 14 includes a first installation through hole 1401, a first lock pin 1402, and a first spring 1403. The first lock pin 1402 is located inside the first installation through hole 1401, and the first spring 1403 tends to push the first lock pin 1402 outwards.

[0048] The position of the first locking mechanism 14 corresponds to the lower locking position. When the lower slider 9 is in its lower locking position, the outer locking pin 1701 in the lower slider 9 abuts against the inner end of the outer end of the first locking pin 1402 correspondingly. Since the restoring force provided by the outer spring 1702 in the lower slider 9 to the outer locking pin 1701 is greater than the restoring force provided by the first spring 1403 to the first locking pin 1402, the outer locking pin 1701 in the lower slider 9 is inserted into the first mounting through hole 1401. The outer locking mechanism 17 in the lower slider 9 cooperates with the first locking mechanism 14 to complete the locking of the lower slider 9 below, thereby locking the lower slider 9 in its lower locking position and keeping the tool arm 2 in the retracted state.

[0049] The second locking mechanism 15 includes a second mounting through hole 1501, a second locking pin 1502, and a second spring 1503. The second locking pin 1502 is located in the second mounting through hole 1501, and the second spring 1503 tends to push the second locking pin 1502 outwards.

[0050] There is no locking mechanism in the upper slider 8, and it can pass through the second locking mechanism 15 smoothly.

[0051] The position of the second locking mechanism 15 corresponds to the upper locking position. When the lower slider 9 is in its upper locking position, the outer locking pin 1701 in the lower slider 9 abuts against the inner end of the outer end of the second locking pin 1502 correspondingly. Since the restoring force provided by the outer spring 1702 in the lower slider 9 to the outer locking pin 1701 is greater than the restoring force provided by the second spring 1503 to the second locking pin 1502, the outer locking pin 1701 in the lower slider 9 is inserted into the second mounting through hole 1501. The outer locking mechanism 17 in the lower slider 9 cooperates with the second locking mechanism 15 to complete the locking of the lower slider 9 above, thereby locking the lower slider 9 in its upper locking position and keeping the tool arm 2 in the deployed state.

[0052] As Figure 7 、 Figure 9 and Figure 10 shown, the expandable underreamer further includes a lower unlocker 18. The outer diameter of the lower unlocker 18 is smaller than the inner diameter of the drill pipe and slightly smaller than the minimum inner diameter of the sliding rod 4. When the expandable underreamer is lowered to the bottom of the pilot hole 20 in the retracted state, the lower unlocker 18 is dropped at the wellhead. Driven by the drilling fluid, the lower unlocker 18 passes through the second locking mechanism 15 smoothly and reaches the first locking mechanism 14. The outer peripheral surface of the lower unlocker 18 forces both the first locking pin 1402 and the outer locking pin 1701 in the lower slider 9 to move outwards. The outer locking pin 1701 in the lower slider 9 withdraws from the first mounting through hole 1401, releasing the locking state of the outer locking mechanism 17 in the lower slider 9. The strong spring 10 quickly pushes the lower slider 9 away from the lower locking position and simultaneously pushes the upper slider 8 upwards. The lower unlocker 18 passes through the first locking mechanism 14 and reaches the guide head 12 and sits in the guide head 12.

[0053] Rotate the drill string while lowering and raising the drill string to create a cavity. During this process, the cutter arms 2 gradually unfold and finally fully unfold. The upper slider 8 slides to the limit block 5, and the lower slider 9 slides to the second locking mechanism 15 and is locked in place, maintaining the fully unfolded state.

[0054] As Figure 8 、 Figure 11 shown, the expandable backreamer further includes an upper unlocker 19. After the backreaming is completed, the upper unlocker 19 is dropped into the drill pipe from the wellhead. The upper unlocker 19 reaches the second locking mechanism 15 under the drive of the drilling fluid and stays there, forcing the second locking pin 1502 and the external locking pin 1701 in the lower slider 9 to move outwards together. The external locking pin 1701 in the lower slider 9 exits the second installation through-hole 1501, releasing the locking state of the lower slider 9 at the second locking mechanism 15. Both the upper slider 8 and the lower slider 9 can slide downwards. Lift the expandable backreamer and pull it into the pilot hole 20, forcing the cutter arms 2 of the expandable backreamer to fold up. Continue to pull out the drill string, and the lower slider 9 will slide down to its lower locking position. The cutter arms 2 change from the unfolded state to the folded state until the drill string is completely pulled out.

[0055] As Figure 12 shown, to prevent the collapse of the large-diameter gob area 21 and ground subsidence, it is necessary to backfill the large-diameter gob area 21 in a timely manner, which is also an effective way to handle the residues. There are three backfilling schemes to choose from: 1. Backfill while backreaming: While pumping drilling fluid into the well, let the backfill material 22 flow to the guide head 12 together with the drilling fluid and spray out from the nozzle 1201 of the guide head 12. The backfill material 22 quickly settles in the gob area to achieve backfilling. The drilling fluid without backfill material enters the cutting working surface of the backreamer and carries the mineral particles to the ground. 2. Alternate backreaming and backfilling: After backreaming a certain length, conduct backfilling. 3. Conduct centralized backfilling after completing all the backreaming operations of a single well. The first two schemes are preferred.

[0056] The backreaming mining method uses the above expandable backreamer to backream the pilot hole 20 and backfill it in a timely manner. The operation steps are generally as follows:

[0057] Step 1: Drill the pilot hole 20 using conventional drilling techniques. Drill the surface section of the pilot hole 20 using conventional drilling techniques, run the surface casing, and cement the well. Then, use conventional drilling techniques to drill the remaining section of the pilot hole 20 to the designed well depth and pull out the drill string. The pilot hole 20 can be a vertical well, a directional well, a horizontal well, or a multilateral well.

[0058] Step 2: Lower the expandable backreamer. Lower the expandable backreamer to the bottom of the pilot hole 20. During this process, the cutter arms 2 of the expandable backreamer are in the folded state.

[0059] Step 3: Unlock. Lower the lower unlocker 18. Driven by the drilling fluid, the lower unlocker 18 quickly reaches and passes over the first locking mechanism 14 of the sliding rod. The strong spring 10 pushes the lower slider 9 to quickly disengage from the locking position, realizing unlocking. The lower unlocker 18 enters the guide head 12 and sits inside the guide head.

[0060] Step 4: Create a cavity and fully expand and lock the cutter arms 2 of the deployable backdrilling tool. While circulating the drilling fluid, rotate the drill string, and at the same time repeatedly lower and raise the drill string to create a cavity until the cutter arms 2 of the deployable backdrilling tool are fully expanded, the upper slider 8 reaches the upper locking position, and the outer locking mechanism 17 of the lower slider 9 cooperates with the second locking mechanism 15 of the sliding rod to complete the locking, locking the cutter arms 2 of the deployable backdrilling tool in the fully expanded state.

[0061] Step 5: Backdrill. Raise the drill string, apply a certain drilling pressure to the deployable backdrilling tool, and start backdrilling. The drilling fluid sprays out from the guide head 12, flows into the cutting working surface of the deployable backdrilling tool, carries the crushed mineral particles into the annular space of the guide well 20, and flows to the ground.

[0062] Step 6: Unlock. After completing backdrilling, wash the well and lower the upper unlocker 19. When the upper unlocker 19 reaches the position of the second locking mechanism 15 of the sliding rod, the locking state of the outer locking mechanism 17 of the lower slider 9 is released.

[0063] Step 7: Retrieve the deployable backdrilling tool. Raise the deployable backdrilling tool, forcing the cutter arms 2 to return to the retracted state, and retrieve the deployable backdrilling tool.

[0064] Step 8: Abandon the well with cement.

[0065] After the oil sand and heavy oil reservoir particles carried to the ground by the drilling fluid are separated from the drilling fluid on the ground, they enter the oil-sand separation system to separate the oil quality therein, and the residue is used as the backfill material 22. The natural gas hydrate particles return with the drilling fluid. During this process, the pressure is continuously released and the temperature is continuously rising, inducing the release of natural gas therein, which enters the natural gas recovery system on the ground. After the underground coal is carried to the ground by the drilling fluid, it is separated from the drilling fluid and enters the coal conveying system.

[0066] The above is only a specific embodiment of the present invention and cannot be used to limit the scope of the invention implementation. Therefore, the replacement of its equivalent components, or the equivalent changes and modifications made according to the protection scope of the present invention, should still fall within the scope covered by the present invention. In addition, the technical features in the present invention, between technical features, between technical features and technical solutions, between technical solutions and technical solutions, and between embodiments and embodiments can be freely combined and used.

Claims

1. A deployable back-drilling device, characterized in that: The deployable drill reverser comprises an upper joint (1), a knife arm (2), a knife assembly (3), a slide bar (4), a transverse support rod (6), an oblique support rod (7), an upper slider (8), a lower slider (9) and a strong spring (10); the upper joint (1) is fixed to the upper end of the slide bar (4); the knife arm (2) is in a strip-shaped structure; the knife assembly (3) is mounted on the knife arm (2); the upper end of the knife arm (2) is hinged to the upper joint (1); the upper slider (8) and the lower slider (9) are ) are sleeved outside the slide bar (4); one end of the transverse support rod (6) is hinged to the middle part of the knife arm (2), and the other end of the transverse support rod (6) is hinged to the upper slide block (8); one end of the oblique support rod (7) is hinged to the middle part of the transverse support rod (6), and the other end of the oblique support rod (7) is hinged to the lower slide block (9); an external locking mechanism (17) is arranged inside the lower slide block (9); a strong spring (10) can push the upper slide block (8) and the lower slide block (9) to slide upward; When the lower slider (9) is located at the lower locking position, the external locking mechanism (17) locks the lower slider (9) and keeps the knife arm (2) in a retracted state; when the lower slider (9) is located at the upper locking position, the external locking mechanism (17) locks the lower slider (9) and keeps the knife arm (2) in an extended state.

2. The deployable back boring tool according to claim 1, characterized in that: The deployable drill reverser comprises a plurality of blade arms (2), the plurality of blade arms (2) are arranged at intervals along the circumference of a slide bar (4), the blade arms (2) correspond to the transverse support rods (6) one by one, and the transverse support rods (6) correspond to the oblique support rods (7) one by one; a plurality of tool assemblies (3) are mounted on the blade arms (2), the plurality of tool assemblies (3) are arranged at intervals along the extension direction of the blade arms (2), and the tool assemblies (3) contain cutting teeth; and a flexible wear-resistant and waterproof baffle (13) is mounted between two adjacent blade arms (2).

3. The deployable back boring tool according to claim 1, characterized in that: The expandable drill reverser also includes a limit block (5), a slide rail (11) and a guide head (12); the limit block (5) is located at the upper part of the slide rod (4), and the limit block (5) limits the upper slider (8) to slide upward to an extreme position; two slide rails (11) are symmetrically processed on the outer side of the slide rod (4) below the limit block (5), and the slide rails (11) cooperate with the inner slide grooves of the upper slider (8) and the lower slider (9), forcing the upper slider (8) and the lower slider (9) to slide axially only along the slide rod (4); the guide head (12) is connected to the lower end of the slide rod (4) by a thread, and a plurality of nozzles (1201) are arranged in the guide head (12).

4. The deployable back boring tool according to claim 1, characterized in that: The strong spring (10) is located between the upper slider (8) and the lower slider (9), and the strong spring (10) is sleeved outside the slide bar (4); the external locking mechanism (17) includes an external locking pin (1701) and an external spring (1702), and the external spring (1702) tends to push the external locking pin (1701) toward the slide bar (4).

5. The deployable back boring tool according to claim 4, characterized in that: A first locking mechanism (14) is arranged inside the side wall of the slide bar (4), and the first locking mechanism (14) corresponds one-to-one with the outer locking mechanism (17) inside the lower slide block (9); the first locking mechanism (14) comprises a first mounting through hole (1401), a first locking pin (1402) and a first spring (1403), the first locking pin (1402) is located inside the first mounting through hole (1401), the first spring (1403) tends to push the first locking pin (1402) outward, and the position of the first locking mechanism (14) corresponds to the lower locking position; When the lower slider (9) is located at the lower locking position, the outer end of the first locking pin (1402) is in corresponding contact with the inner end of the outer locking pin (1701) in the lower slider (9), and the restoring force provided by the outer spring (1702) in the lower slider (9) to the outer locking pin (1701) is greater than the restoring force provided by the first spring (1403) to the first locking pin (1402). The outer locking pin (1701) in the lower slider (9) is inserted into the first mounting through hole (1401), so that the lower slider (9) enters a locked state, and the lower slider (9) is locked in the lower locking position.

6. The deployable back boring tool according to claim 5, characterized in that: A second locking mechanism (15) is also provided in the side wall of the slide bar (4), and the second locking mechanism (15) corresponds one-to-one to the outer locking mechanism (17) in the lower slide block (9); the second locking mechanism (15) comprises a second mounting through hole (1501), a second locking pin (1502) and a second spring (1503), the second locking pin (1502) is located in the second mounting through hole (1501), and the second spring (1503) tends to push the second locking pin (1502) outward, and the position of the second locking mechanism (15) corresponds to the upper locking position; When the upper slider (8) slides to the upper locking position, the outer end of the second locking pin (1502) abuts against the inner end of the outer locking pin (1701) in the lower slider (9), and the restoring force provided by the outer spring (1702) in the lower slider (9) to the outer locking pin (1701) is greater than the restoring force provided by the second spring (1503) to the second locking pin (1502). The outer locking pin (1701) in the lower slider (9) is inserted into the second mounting through hole (1501), so that the lower slider (9) enters a locking state, and the lower slider (9) is locked in the upper locking position.

7. A back-drilling mining method, characterized in that: The reverse drilling mining method uses the deployable reverse drilling device described in claim 1 to reverse drill the guide well (20) and promptly backfill the large-diameter goaf (21). The operation steps are as follows: Step 1, drilling a pilot well (20) using conventional drilling technology; Step 2, lowering the deployable drill bit to the bottom of the guide well (20), during which the knife arm (2) of the deployable drill bit is in a retracted state; Step 3, placing the lower unlocker (18) to unlock; Step 4: Create a cavity, and allow the blade arm (2) of the deployable drill to be fully deployed and locked; Step 5: Back drilling, the drilling fluid carries the crushed mineral particles into the annular space of the pilot well (20) and flows to the ground; Step 6, placing an unlocker (19) to release the knife arm (2) of the deployable drill reverser from the deployed state; Step 7, pulling out the deployable back boring device; Step 8. Abandon the well with cement.

8. The reverse drilling mining method according to claim 7, characterized in that: The backfilling includes one of the following three methods: The first method is backfilling while drilling: while the drilling fluid is pumped into the well, the backfill material (22) is allowed to flow to the guide head (12) together with the drilling fluid, and is ejected from the nozzle (1201) of the guide head (12). The backfill material (22) quickly settles in the goaf (21) to achieve backfilling. The drilling fluid without the backfill material enters the cutting working face of the backdrill and carries the mineral particles to the ground. The second is to alternate back-drilling and back-filling: after completing a certain length of back-drilling, back-filling is performed; The third is to concentrate on backfilling after completing all reverse drilling operations in a single well.

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