Tool for drilling well first and then inversely reaming in one-time well descending

Abstract

The utility model discloses a tool for drilling a well first and then inversely reaming in one-time well descending, and belongs to the technical field of oil and gas drilling, oil and gas exploitation and mining. The tool comprises a reverse reamer and a drill bit, wherein the reverse reamer comprises a tool arm, a supporting rod, a sliding rod, a sliding block and a flexible wear-resistant waterproof baffle. The supporting rod supports the unfolded cutter arm, the sliding block slides up and down along the sliding rod, and an outer locking mechanism is arranged in the sliding block and used for achieving locking and unlocking of the sliding block at the lower locking position and the upper locking position of the sliding rod; the flexible wear-resistant waterproof baffle is mounted between the two adjacent cutter arms; according to the one-time well descending first drilling and then reverse reaming tool, one-time well descending firstly uses the drill bit to drill a guide well with the small diameter, then the expanded reverse reaming device is used for reverse reaming, large drilling pressure, torque and displacement are not needed in the whole process, drilling cuttings always go upwards through an annulus with the small diameter, the well drilling efficiency can be improved, the cuttings carrying effect of drilling fluid can be improved, and the drilling efficiency is improved. The shaft bareness time is shortened, and the shaft instability risk is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to oil and gas drilling, oil and gas exploitation, mining technical field, concretely is a kind of tool of drilling well first and then reaming eye once downhole. BACKGROUND

[0002] For the scale benefit development deep layer super deep layer oil and gas resources and to deep ground, it is higher to require safe, efficient and economic deep well, super deep well, extra deep well drilling. Deep well, super deep well, extra deep well usually need to use large-diameter upper wellbore. With traditional drilling technology, large-diameter upper wellbore needs to apply large drilling pressure, large torque and large displacement. Even so, drilling efficiency is often low, wellbore exposure time is long, and the risk of wellbore instability is large. Traditional large-diameter upper wellbore means large annulus, which is not conducive to efficient uphole of drilling cuttings. SUMMARY

[0003] In order to improve drilling efficiency, the utility model provides a tool of drilling well first and then reaming eye once downhole, which can realize drilling a smaller guide well first and then reaming eye once downhole, without so large drilling pressure, torque and displacement, so that the drilling cuttings always pass through the smaller annulus uphole, which can improve drilling efficiency, improve drilling fluid cuttings carrying effect, shorten wellbore exposure time and reduce wellbore instability risk.

[0004] The technical scheme adopted by the utility model embodiment to solve its technical problem is:

[0005] A tool of drilling well first and then reaming eye once downhole, comprising an upper and lower reaming eye device and a drill bit, the reaming eye device comprises a slide rod, a cutter arm, a support rod and a slide block, a plurality of cutter arms are arranged along the circumference of the slide rod, the upper end of the cutter arm is hinged to the slide rod, the lower end of the cutter arm is hinged to the upper end of the support rod, the lower end of the support rod is hinged to the slide block, the slide block is sleeved outside the slide rod, the slide block can slide up and down relative to the slide rod, and an external locking mechanism is arranged in the slide block; when the slide block is located at the lower locking position, the external locking mechanism can lock the slide block at the lower locking position and keep the cutter arm in a folded state; when the slide block is located at the upper locking position, the external locking mechanism can lock the slide block at the upper locking position and keep the cutter arm in an unfolded state.

[0006] The drill bit is a roller bit, a PDC bit or a hybrid bit, and the drill bit can drill a guide well. The rock breaking working surface and the lower end of the cutter arm are both provided with cutting teeth.

[0007] A pair of ear seats are arranged on the outer side of the upper part of the slide rod, a limiting block is arranged on the outer side of the middle part of the slide rod, a slide rail is arranged on the outer side of the lower part of the slide rod, the upper end of the cutter arm is hinged to the ear seat, the limiting block limits the upper locking position of the slide block, and the slide rail guides the slide block to only slide up and down, and together with the support rod, the cutter arm bears torque.

[0008] The outer locking mechanism comprises an outer locking pin and an outer spring, the outer spring tends to push the outer locking pin towards the slide rod.

[0009] The slide rod is provided with lower locking mechanisms corresponding to the outer locking mechanisms, each lower locking mechanism comprises a lower mounting through hole, a lower locking pin and a lower spring, the lower locking pin is located in the lower mounting through hole, and the lower spring tends to push the lower locking pin outward; when the sliding block slides to the lower locking position, the outer end of the lower locking pin corresponds to and abuts against the inner end of the outer locking pin, the restoring force provided by the outer spring to the outer locking pin is greater than the restoring force provided by the lower spring to the lower locking pin, and the outer locking pin can be inserted into the lower mounting through hole to lock the sliding block at the lower locking position.

[0010] The slide rod is provided with upper locking mechanisms corresponding to the outer locking mechanisms, each upper locking mechanism comprises an upper mounting through hole, an upper locking pin and an upper spring, the upper locking pin is located in the upper mounting through hole, and the upper spring tends to push the upper locking pin outward; when the sliding block slides to the upper locking position, the outer end of the upper locking pin corresponds to and abuts against the inner end of the outer locking pin, the restoring force provided by the outer spring to the outer locking pin is greater than the restoring force provided by the upper spring to the upper locking pin, and the outer locking pin can be inserted into the upper mounting through hole to lock the sliding block at the upper locking position.

[0011] The inner diameter of the upper part of the slide rod is greater than the inner diameter of the lower part of the slide rod, and an inner wall shoulder is formed above the lower locking mechanism.

[0012] The once-down-the-well first-drilling-then-reaming tool further comprises a lower unlocker, after the lower unlocker is put into the drill string at the well mouth, the lower unlocker can reach the inner wall shoulder under the driving of the drilling fluid and is seated at the inner wall shoulder, forcing the lower locking pin and the outer locking pin to move outward together, under the combined action of the centrifugal force and the drilling pressure after the drill string is rotated and the drilling pressure is applied, the cutter arm tends to unfold, driving the sliding block to move upward and away from the lower locking position, so that the reamer transitions from the folded state to the unfolded state, the drill string is continuously rotated and lowered and raised, a cavity is formed at the bottom of the well until the cutter arm is completely unfolded, at this time, the sliding block reaches the upper locking position and is blocked by the limiting block, and the cutter arm is locked in the completely unfolded state; the lower unlocker is a full-dissolvable unlocker, the lower unlocker is made of a full-dissolvable material, the lower unlocker has a slow-release function, and the lower unlocker can only begin to dissolve after the cavity is formed, so that the lower sliding block will not be relocked at the lower locking position during the cavity forming process.

[0013] The once-down-the-well first-drilling-then-reaming tool further comprises an upper unlocker, after the reaming is completed, the upper unlocker is put into the drill string at the well mouth, the upper unlocker reaches the inner wall shoulder under the driving of the drilling fluid and is seated at the inner wall shoulder, forcing the upper locking pin and the outer locking pin to move outward together, releasing the unfolded state of the reamer, so that the reamer can be taken out from the well; the upper end of the upper unlocker is provided with a fishing head.

[0014] The reverse reaming device also comprises flexible wear-resistant waterproof baffles, which are installed between two adjacent cutter arms, have a fan-shaped structure, can be folded with the folding of the cutter arms, and can be unfolded with the unfolding of the cutter arms.

[0015] The beneficial effects of the embodiment of the utility model are that the once-downhole first-drilling then-reverse-reaming tool can realize once-downhole first-drilling of a guide well with a smaller diameter and then reverse reaming, does not need so large drilling pressure, torque and displacement, lets the drilling cuttings always return through the annulus with a smaller diameter, can improve the drilling efficiency, can improve the drilling fluid cuttings carrying effect, shortens the wellbore exposure time and reduces the wellbore instability risk. BRIEF DESCRIPTION OF DRAWINGS

[0016] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the utility model, and together with the specific embodiment of the utility model and its description serve to explain the utility model, and do not constitute an improper limitation on the utility model.

[0017] Figure 1 is a structural schematic view of the reverse reaming device of the once-downhole first-drilling then-reverse-reaming tool in a folded state.

[0018] Figure 2 is a structural schematic view of the reverse reaming device of the once-downhole first-drilling then-reverse-reaming tool in an unfolded state.

[0019] Figure 3 is a structural schematic view of the slide rod.

[0020] Figure 4 is a structural schematic view of the slide block.

[0021] Figure 5 is a structural schematic view of the outer locking mechanism.

[0022] Figure 6 is a schematic view of the lower unlocking device unlocking the outer locking mechanism.

[0023] Figure 7 is a schematic view of the upper unlocking device unlocking the outer locking mechanism.

[0024] Figure 8 is a schematic view of the lower unlocking device.

[0025] Figure 9 is a schematic view of the flexible wear-resistant waterproof baffle.

[0026] The following is an explanation of the reference signs:

[0027] 1. Drill bit; 2. Reamer; 3. Lower unlocker; 4. Upper unlocker;

[0028] 21. Slide rod; 22. Knife arm; 23. Slider; 24. External locking mechanism; 25. Ear seat; 26. Limiting block; 27. Slide rail; 28. Lower locking mechanism; 29. ​​Upper locking mechanism; 210. Flexible wear-resistant and waterproof baffle;

[0029] 31. Outer large diameter section; 32. Outer ring transition section; 33. Outer small diameter section;

[0030] 41. Salvage head; 42. Conical structure;

[0031] 211. Inner wall shoulder;

[0032] 221. Support rod; 222. Cutting teeth;

[0033] 231. Slide groove;

[0034] 241. External locking pin; 242. External spring;

[0035] 281. Lower mounting through hole; 282. Lower locking pin; 283. Lower spring;

[0036] 291. Mounting through hole; 292. Locking pin; 293. Spring. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] like Figures 1 to 5 As shown in the embodiment of this utility model, a tool for drilling first and then reaming in a single run-in well includes a reamer 2 and a drill bit 1 arranged vertically. The reamer 2 includes a slide rod 21, a cutter arm 22, a support rod 221, and a slider 23. Multiple cutter arms 22 are arranged circumferentially along the slide rod 21, with the upper end of the cutter arm 22 hinged to the slide rod 21. The length of the cutter arm 22 depends on the diameter of the reamed well. The upper end of the support rod 221 is hinged to the lower part of the cutter arm 22, and the lower end of the support rod 221 is hinged to the slider 23. The slider 23 is sleeved on the slide rod 21 and can slide up and down along the slide rod 21. An external locking mechanism 24 is provided inside the slider 23. When the slider 23 is in the lower locking position, the external locking mechanism 24 locks the slider 23 in the lower locking position and keeps the cutter arm 22 in a retracted state. When the slider 23 is in the upper locked position, the outer locking mechanism 24 locks the slider 23 in the upper locked position and keeps the blade arm 22 in the extended state.

[0039] In the embodiment, the drill bit 1 can be a roller bit, a PDC bit or a hybrid bit, which is used to drill a relatively small pilot hole for facilitating accurate and efficient directional drilling. The reamer 2 is connected to the drill bit 1 by threads, and the upper end of the reamer 2 is internally threaded for connecting a drill string. When the cutter arm 22 is in the collapsed state, the outer diameter of the reamer 2 is slightly smaller than the outer diameter of the drill bit 1, and the rock-breaking working surface and the lower end of the cutter arm 22 are both provided with cutting teeth 222, which can be milling teeth, insert teeth, PDC cutting teeth or hybrid teeth, for breaking rocks during the reaming process. The cutting teeth at the lower end of the cutter arm 22 are used to create a cavity, which facilitates the complete expansion of the cutter arm 22 and locks it in the fully expanded state.

[0040] As shown in Figures 3 to 5 the upper outer side of the slide bar 21 is provided with pairs of ear seats 25, and multiple pairs of ear seats 25 are arranged along the circumference of the slide bar 21. The middle outer side of the slide bar 21 is provided with a limiting block 26, and the lower outer side of the slide bar 21 is provided with a slide rail 27. The upper end of the cutter arm 22 is hingedly connected to the ear seats 25 one by one, and the support bar 221 ensures that the cutter arm 22 can withstand sufficient weight on bit when fully expanded. The limiting block 26 defines the upper locking position of the slide block 23. The slide rail 27 guides the slide block 23 to slide up and down only, and together with the support bar 221 enables the cutter arm 22 to withstand large torque.

[0041] The inner side of the slide block 23 is provided with a sliding groove 231, which cooperates with the slide rail 27 to limit the slide block 23 to slide along the slide rail 27. The slide block 23 is internally provided with an outer locking mechanism 24, which includes an outer locking pin 241 and an outer spring 242, and the outer spring 242 tends to push the outer locking pin 241 towards the slide bar 21.

[0042] As shown in Figures 1 to 5 the slide bar 21 is provided with a lower locking mechanism 28, which corresponds to the outer locking mechanism 24 one by one. The lower locking mechanism 28 includes a lower mounting through hole 281, a lower locking pin 282 and a lower spring 283. The lower locking pin 282 is located in the lower mounting through hole 281, and the lower spring 283 tends to push the lower locking pin 282 outward.

[0043] When the slide block 23 slides to the lower locking position, the outer end of the lower locking pin 282 abuts against the inner end of the outer locking pin 241 one by one, the restoring force provided by the outer spring 242 to the outer locking pin 241 is greater than the restoring force provided by the lower spring 283 to the lower locking pin 282, and the outer locking pin 241 can be inserted into the lower mounting through hole 281 to lock the slide block 23 in the lower locking position, so that the cutter arm 22 remains in the collapsed state.

[0044] The slide rod 21 is provided with upper locking mechanisms 29 corresponding to the outer locking mechanisms 24, which contain upper mounting through holes 291, upper locking pins 292 and upper springs 293. The upper locking pins 292 are located in the upper mounting through holes 291, and the upper springs 293 tend to push the upper locking pins 292 outward.

[0045] When the slide block 23 slides to the upper locking position, the outer end of the upper locking pin 292 abuts against the inner end of the outer locking pin 241 corresponding to each other, and the restoring force provided by the outer spring 242 to the outer locking pin 241 is greater than the restoring force provided by the upper spring 293 to the upper locking pin 292. The outer locking pin 241 can be inserted into the upper mounting through hole 291 to lock the slide block 23 in the upper locking position, so that the cutter arm 22 remains in the unfolded state.

[0046] The inner diameter of the upper part of the slide rod 21 is slightly larger than that of the lower part, forming an inner wall shoulder 211 above the lower locking mechanism 28.

[0047] As shown in Figure 6 and Figure 8 , the once-down-the-well first-drilling-then-reaming tool further comprises a lower unlocker 3. To release the collapsed state of the reamer 2, the lower unlocker 3 is put into the drill string at the wellhead. The outer circumferential surface of the lower unlocker 3 contains an outer large-diameter section 31, an outer annular transition section 32 and an outer small-diameter section 33 connected in sequence from top to bottom. The lower unlocker 3 reaches the inner wall shoulder 211 under the drive of the drilling fluid and is seated there, forcing the lower locking pin 282 and the outer locking pin 241 to move outward together. The drill string is rotated and drilling pressure is applied. Under the combined action of centrifugal force and drilling pressure, the cutter arm 22 tends to unfold, driving the slide block 23 to move upward and out of the lower locking position, so that the reamer 2 transitions from the collapsed state to the unfolded state. The drill string is continuously rotated and lowered and raised, creating a cavity at the bottom of the well until the cutter arm 22 is fully unfolded. At this time, the slide block reaches the upper locking position and is blocked by the limiting block 26 and locked in the fully unfolded state.

[0048] The lower unlocker 3 is a fully soluble unlocker made of existing fully soluble materials in water (for example, the material of the existing soluble bridge plug can be used), which has a slow-release function and begins to dissolve only after the cavity is created, so that the lower slide block 23 will not be relocked in the lower locking position during the cavity creation process. The purpose of using the soluble lower unlocker 3 is to free the drilling fluid flow passage inside the slide rod and reduce the flow resistance during the reaming process, and to clear the inner wall shoulder 211 for the following upper unlocker 4, facilitating the reliable seating of the upper unlocker 4 there.

[0049] As shown in Figure 7As shown, the first downhole drilling and then back reaming tool also includes an upper unlocking device 4, and the lower end of the upper unlocking device 4 is provided with a tapered structure 42. After the back reaming is completed, in order to release the expanded state of the back reamer 2, the upper unlocking device 4 is put into the drill string at the wellhead. The upper unlocking device 4 reaches the inner wall shoulder 211 under the driving of the drilling fluid and is seated there, forcing the upper locking pin 292 and the outer locking pin 241 to move outward together, thereby releasing the expanded state of the back reamer 2, so that the back reamer 2 can be taken out from the downhole. The upper end of the upper unlocking device 4 is provided with a fishing head 41, which facilitates the release of the expanded state of the back reamer 2 during the back reaming process. The upper unlocking device 4 is made of non-soluble material.

[0050] As shown in the drawings, Figure 9 The back reamer 2 also contains a flexible wear-resistant waterproof baffle 210. The flexible wear-resistant waterproof baffle 210 is fan-shaped and is installed between two adjacent cutter arms 22. It can be folded with the folding of the cutter arms 22, unfolded with the unfolding of the cutter arms 22, and in a taut state. During the back reaming process, the drilling fluid is sprayed from the drill bit 1, returns upward through the enlarged annulus, flows through the back reamer 2, and then flows to the ground through the smaller diameter annulus. The main functions of the flexible wear-resistant waterproof baffle 210 are: 1. After the cutter arms 22 are fully unfolded, the flexible wear-resistant waterproof baffle 210 changes the flow direction of the drilling fluid, guides the drilling fluid to flow to the cutting teeth 222 as completely as possible, and carries the cuttings upward, while cleaning and cooling the cutting teeth 222. 2. The flexible wear-resistant waterproof baffle 210 blocks the cuttings from falling into the enlarged wellbore; 3. The flexible wear-resistant waterproof baffle 210 in a taut state forms a whole on the working surface of the back reamer 2, and the cutter arms 22 are circumferentially restrained, ensuring that the back reamer 2 can withstand large torques.

[0051] The operation steps of the back reaming operation using the first downhole drilling and then back reaming tool are as follows:

[0052] 1. Connect the drill bit 1 and the back reamer 2. The drill bit 1 and the back reamer 2 are connected by threads, and the upper end of the back reamer 2 is also connected to the drill string by threads. Initially, the cutter arms 22 are in a folded state, and the sliding block 23 is locked in the lower locking position.

[0053] 2. Drill and drill the pilot hole. Drill a smaller diameter pilot hole using the drill bit 1 until the designed well depth is reached.

[0054] 3. Unlocking. Raise the drill string 1-3 meters, put in the lower unlocking device 3, start the pump, and pump the lower unlocking device 3 downward until the lower unlocking device 3 is seated on the inner wall shoulder 211, and the lower unlocking device 3 releases the locking state of the sliding block 23.

[0055] 4. Cavity creation, the arms 22 are fully deployed and locked. Rotating the drill string, the arms 22 deploy under the action of centrifugal force, contact the well wall. While rotating the drill string and circulating the drilling fluid, a certain drilling pressure is applied downward, the cavity creation is started. The process of lowering and raising the drill string is repeated until the cavity creation is completed, the arms 22 are fully deployed, the slide 23 is driven to the upper locking position and is locked there, maintaining the fully deployed state of the arms 22.

[0056] 5. Backreaming. While rotating the drill string and circulating the drilling fluid, a certain upward pulling force (upward drilling pressure) is applied to the backreamer 2, the backreaming is started, until the backreaming operation is completed.

[0057] 6. Unlocking and tripping. The pump is stopped, the upper unlocker 4 is lowered downward. The pump is started, the upper unlocker 4 is pumped downward until the upper unlocker 4 is seated on the inner wall shoulder 211, the upper unlocker 4 releases the locking state of the slide 23. Tripping, the smaller upper wellbore forces the arms 22 to fold, the tripping process continues.

[0058] The long-arm backreamer 2 (backreamer) can be used for backreaming mining of relatively loose underground resources such as oil sands, heavy oil, natural gas hydrate, deep coal, etc., that is, solid mineral fluidization mining, that is, using the long-arm backreamer 2 to backream the pilot well to form a large-diameter mined-out area, as many mineral particles as possible are carried to the ground by the drilling fluid. First, the drill bit 1 is used to drill the pilot well to the designed depth, then the lower unlocker 3 is lowered to release the locking state of the long-arm backreamer 2 in the folded state, the drill string is lowered and raised while rotating the drill string to create a cavity, after the cavity creation is completed, the long-arm backreamer 2 is fully deployed and locked in the fully deployed state. Start backreaming. During backreaming, the drilling fluid containing backfill material is sprayed from the drill bit 1, the backfill material quickly settles in the large-diameter mined-out area, timely backfilling the large-diameter mined-out area, the drilling fluid without backfill material enters the cutting working surface of the long-arm backreamer 2, carrying the broken mineral particles to the ground through the annulus of the pilot well. After backreaming is completed, the upper unlocker 4 is lowered to release the locking state of the fully deployed long-arm backreamer 2, and tripping is started.

[0059] The above is only a specific embodiment of the present application, which cannot limit the scope of the application, so the replacement of equivalent components or equivalent changes and modifications made within the scope of the present application should still belong to the scope of the present application. In addition, the technical features in the present application can be freely combined with each other, and the technical features can be freely combined with each other.

Claims

1. A tool for drilling first and then reaming in a single well run, characterized in that, The tool comprises an upper and lower reaming device (2) and a drill bit (1), the reaming device (2) comprises a slide rod (21), cutter arms (22), a support rod (221) and a slide block (23), a plurality of cutter arms (22) are arranged along the circumference of the slide rod (21), the upper end of the cutter arm (22) is hinged to the slide rod (21), the lower end of the cutter arm (22) is hinged to the upper end of the support rod (221), the lower end of the support rod (221) is hinged to the slide block (23), the slide block (23) is sleeved outside the slide rod (21), the slide block (23) can slide up and down relative to the slide rod (21), and the slide block (23) is provided with an external locking mechanism (24) inside. When the slide block (23) is located at the lower locking position, the external locking mechanism (24) can lock the slide block (23) at the lower locking position and keep the cutter arms (22) in a folded state; when the slide block (23) is located at the upper locking position, the external locking mechanism (24) can lock the slide block (23) at the upper locking position and keep the cutter arms (22) in an unfolded state.

2. The run-once, drill-first, then back-ream tool of claim 1, wherein, The drill bit (1) is a roller bit, a PDC bit or a hybrid bit, the drill bit (1) can drill a pilot hole, and the rock breaking working surface and the lower end of the cutter arm (22) are provided with cutting teeth (222).

3. The run-once, drill-first, then back-ream tool of claim 1, wherein, The upper outer side of the slide rod (21) is provided with a pair of ear seats (25), the middle outer side of the slide rod (21) is provided with a limiting block (26), and the lower outer side of the slide rod (21) is provided with a slide rail (27), the upper end of the cutter arm (22) is hinged to the ear seat (25), the limiting block (26) defines the upper locking position of the slide block (23), the slide rail (27) guides the slide block (23) to slide only up and down, and the slide rail (27) and the support rod (221) together bear the torque of the cutter arm (22).

4. The run-in-first drill-out-later tool of claim 1, wherein, The external locking mechanism (24) comprises an external locking pin (241) and an external spring (242), and the external spring (242) tends to push the external locking pin (241) towards the slide rod (21).

5. The run-in-first drill-out-later tool of claim 4, wherein, The slide rod (21) is provided with a lower locking mechanism (28) inside, the lower locking mechanism (28) corresponds to the external locking mechanism (24), the lower locking mechanism (28) comprises a lower mounting through hole (281), a lower locking pin (282) and a lower spring (283), the lower locking pin (282) is located in the lower mounting through hole (281), and the lower spring (283) tends to push the lower locking pin (282) outward; When the slide block (23) slides to the lower locking position, the outer end of the lower locking pin (282) corresponds to and abuts against the inner end of the external locking pin (241), the restoring force provided by the external spring (242) for the external locking pin (241) is greater than the restoring force provided by the lower spring (283) for the lower locking pin (282), and the external locking pin (241) can be inserted into the lower mounting through hole (281) to lock the slide block (23) at the lower locking position.

6. The run-in-first drill-out-later tool of claim 5, wherein, The slide rod (21) is provided with upper locking mechanisms (29) corresponding to the outer locking mechanisms (24), the upper locking mechanisms (29) include upper mounting through holes (291), upper locking pins (292) located in the upper mounting through holes (291), and upper springs (293) tending to push the upper locking pins (292) outward; When the sliding block (23) slides to the upper locking position, the outer end of the upper locking pin (292) corresponds to and abuts against the inner end of the outer locking pin (241), the restoring force provided by the outer spring (242) to the outer locking pin (241) is greater than the restoring force provided by the upper spring (293) to the upper locking pin (292), and the outer locking pin (241) can be inserted into the upper mounting through hole (291), thereby locking the sliding block (23) in the upper locking position.

7. The run-once, drill-first, back-ream tool of claim 6, wherein, The inner diameter of the upper part of the slide rod (21) is greater than the inner diameter of the lower part of the slide rod (21), and an inner wall shoulder (211) is formed above the lower locking mechanism (28).

8. The run-once, drill-first, back-ream tool of claim 7, wherein, The tool further comprises a lower unlocker (3), after the lower unlocker (3) is put into the drill string at the wellhead, the lower unlocker (3) can reach the inner wall shoulder (211) under the driving of the drilling fluid and be seated at the inner wall shoulder (211), forcing the lower locking pin (282) and the outer locking pin (241) to move outward together, under the combined action of the centrifugal force and the drilling pressure after the drill string is rotated and drilling pressure is applied, the blade arm (22) tends to unfold, driving the sliding block (23) to move upward and disengage from the lower locking position, so that the reaming device (2) transitions from the folded state to the unfolded state, and the drill string is continuously rotated and lowered and raised, a cavity is formed at the bottom of the well until the blade arm (22) is completely unfolded, at this time, the sliding block (23) reaches the upper locking position and is blocked by the limiting block (26), and the blade arm (22) is locked in the completely unfolded state; The lower unlocker (3) is a fully soluble unlocker, the lower unlocker (3) is made of a fully soluble material, the lower unlocker (3) has a slow-release function, and the lower unlocker (3) can only begin to dissolve after the cavity is formed, so that the lower sliding block (23) will not be relocked in the lower locking position during the cavity forming process.

9. The run-once, drill-first, back-ream tool of claim 7, wherein, The tool further comprises an upper unlocker (4), after the reaming is completed, the upper unlocker (4) is put into the drill string at the wellhead, the upper unlocker (4) reaches the inner wall shoulder (211) under the driving of the drilling fluid and is seated at the inner wall shoulder (211), forcing the upper locking pin (292) and the outer locking pin (241) to move outward together, releasing the unfolded state of the reaming device (2), so that the reaming device (2) can be taken out from the well; The upper end of the upper unlocker (4) is provided with a fishing head (41).

10. The run-in-first drill-out-later tool of claim 1, wherein, The reverse reamer (2) further comprises a flexible wear-resistant waterproof baffle (210) installed between two adjacent cutter arms (22), the flexible wear-resistant waterproof baffle (210) is in a fan-shaped structure, the flexible wear-resistant waterproof baffle (210) can be folded with the folding of the cutter arms (22), and the flexible wear-resistant waterproof baffle (210) can also be unfolded with the unfolding of the cutter arms (22).

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