Double-wall drill pipe for oil drilling

Abstract

The present invention belongs to the technical field of drill pipes, specifically a double-wall drill pipe for oil drilling, which includes an outer pipe. An inner pipe is inserted into the outer pipe. Two groups of limiting components are arranged on the inner wall of the outer pipe along the up-and-down direction. The limiting components are composed of a plurality of limiting blocks, and the plurality of limiting blocks are evenly fixedly connected to the inner wall of the outer pipe, and a blocking block is fixedly connected to the top of the limiting block. When a blowout occurs, the liquid in the well will be ejected out of the wellhead simultaneously through the inside of the inner pipe and the annular gap between the inner pipe and the outer pipe. During this process, the sealing ring can move upward, so as to cooperate with the sealing groove on the sealing ring to seal the annular gap between the inner pipe and the outer pipe, and the first sealing plate can move upward and be connected to the second sealing plate, so that the inner pipe can be closed under the mutual cooperation of the first sealing plate and the second sealing plate, thereby avoiding the occurrence of well kick accidents.

Description

Technical Field

[0001] The present invention belongs to the technical field of drill pipes, and particularly relates to double-wall drill pipes for oil drilling. Background Art

[0002] Double-wall drill pipes, also known as double-layer drill pipes, are composed of an inner and an outer layer of drill pipes (referred to as the inner pipe and the outer pipe). An annular gap is formed between the inner and outer pipes, which is a channel for pumping flushing medium to the bottom of the hole during hydraulic rock drilling and core sampling drilling. The central hole of the inner pipe is for discharging the flushing medium. The double-wall drill pipes are fixed as a whole. Each double-wall drill pipe is connected by the threads of the outer pipe to ensure the transmission of torque and pressure, while the inner pipes are mostly connected by insertion, generally only serving the function of circulating the flushing medium.

[0003] For example, a Chinese patent with the publication number CN211500953U proposed a double-wall drill pipe for oil drilling, "including an upper joint of the outer pipe, an outer pipe body, a lower joint of the outer pipe, an inner sleeve, an upper joint of the inner pipe, an inner pipe body, and a lower joint of the inner pipe". The double-wall drill pipe for oil drilling proposed in this patent can quickly assemble two drill pipes during use, fix the two drill pipes well, prevent the drill pipes from shifting, ensure the normal progress of oil drilling work, has a simple structure, can disassemble the double-wall drill pipe, can be transformed into a common drill pipe for use, can meet the mechanical performance requirements under the working conditions of oil drilling construction, and at the same time has the characteristic of small flow resistance;

[0004] Although the double-wall drill pipe for oil drilling proposed in the above patent solves some problems existing in the current double-wall drill pipes for oil drilling, there are still the following deficiencies in actual use:

[0005] 1. Since the bottom of the upper joint of the outer pipe in the above patent is fixedly connected to the top of the outer pipe body by friction welding, it is very inconvenient to disassemble the inner and outer pipes;

[0006] 2. Since the existing double-wall drill pipes for oil drilling lack a suitable blowout preventer device, when a blowout occurs, the existing double-wall drill pipes for oil drilling cannot well seal the wellhead, thus causing a well kick accident.

[0007] Therefore, it is very necessary to invent a double-wall drill pipe for oil drilling to solve the above problems. Summary of the Invention

[0008] In view of the above problems, the present invention provides a double-wall drill pipe for oil drilling to solve the problems raised in the above background art.

[0009] To achieve the above object, the present invention provides the following technical solution: a double-wall drill pipe for oil drilling, including an outer pipe, an inner pipe is inserted into the outer pipe, two groups of limiting components are arranged on the inner wall of the outer pipe along the up and down direction, the limiting components are composed of a plurality of limiting blocks, and the plurality of limiting blocks are evenly fixedly connected to the inner wall of the outer pipe, and a blocking block is fixedly connected to the top of the limiting block. A connecting device matching the number of the limiting blocks is arranged at a position on the outer wall of the inner pipe opposite to the limiting components. An anti-blowout device is arranged at a position near the top of the inner pipe. A plurality of limiting plates are annularly distributed on the outer surface of the inner pipe near the top, and the limiting plates are fixedly connected to the outer wall of the inner pipe. A circular limiting groove is opened at a position on the inner wall of the outer pipe opposite to the plurality of limiting plates. The top groove wall of the limiting groove is communicated with the top of the outer pipe, and the plurality of limiting plates are slidably inserted into the limiting groove.

[0010] Further, the connecting device includes a clamping block, the clamping block is fixedly connected to the outer wall of the inner pipe, a clamping plate is arranged at the bottom of the clamping block, the clamping plate is fixedly connected to the outer wall of the inner pipe, and the distance between the clamping plate and the clamping block matches the height of the limiting block.

[0011] Further, the anti-blowout device includes a sealing ring, the sealing ring is located at the top of the limiting plate and sleeved on the outside of the inner pipe. An annular protrusion is arranged at the top of the sealing ring, the annular protrusion is fixedly sleeved on the outer wall of the inner pipe, and a sealing groove matching the annular protrusion is opened at the top of the sealing ring. Fixing rods are fixedly connected to the inner walls on both sides of the sealing ring. A strip-shaped sliding groove is vertically penetrated through the inner pipe at a corresponding position of the fixing rods, and the fixing rods are inserted through the sliding groove. The opposite ends of the two fixing rods are fixedly connected to the same sealing pipe, and the sealing pipe is slidably inserted into the inner pipe. A first sealing plate is fixedly connected to the inner side of the sealing pipe near the top position. A plurality of first through holes are penetrated through the first sealing plate. A second sealing plate is arranged at the top of the first sealing plate, the second sealing plate is fixedly connected to the inner wall of the inner pipe. A plurality of second through holes are penetrated through the second sealing plate, and the plurality of second through holes are staggered with the plurality of first through holes one by one. A plurality of inserting blocks are fixedly connected to the bottom of the second sealing plate, and the plurality of inserting blocks correspond to and match the plurality of first through holes one by one. An L-shaped groove is opened at the bottom groove wall of the sliding groove, and the horizontal section of the L-shaped groove is communicated with the inside of the inner pipe. A telescopic block is slidably inserted into the vertical section of the L-shaped groove, the top of the telescopic block is fixedly connected to the bottom of the fixing rod, a positioning block is slidably inserted into the horizontal section of the L-shaped groove, a positioning hole is opened on the outer wall of the sealing pipe at a corresponding position of the positioning block, and a spring is connected between the end of the positioning block far away from the positioning hole and the vertical section of the L-shaped groove.

[0012] Further, the top views of the clamping block and the clamping plate are the same, and the width of the clamping block is smaller than the distance between adjacent two limiting blocks. A plurality of roller shafts are rotatably connected between the clamping block and the clamping plate, and the roller shafts are pressed against the limiting blocks.

[0013] Furthermore, the opposite sides of the locking block and the limiting block are both designed with arc surfaces, and the curvature of the two arc surfaces is the same and fits well.

[0014] Furthermore, the contact positions of the telescopic block and the positioning block are both designed as inclined surfaces, and the projection lengths of the two along the vertical direction are greater than the distance between the free end of the positioning block and the positioning hole in its natural state.

[0015] Furthermore, the inner diameter of the top of the outer tube is the same as the outer diameter of the bottom thereof, and the inner wall of the top of the outer tube and the outer wall of the bottom of the outer tube are respectively provided with mutually matching threads and threads.

[0016] Furthermore, the outer diameter of the bottom of the inner tube matches the inner diameter of the top thereof, and a sealing sleeve is fixedly sleeved on the outer wall of the bottom of the inner tube.

[0017] Furthermore, the outer diameter of the sealing ring matches the inner diameter of the outer tube, and the distance from the sealing ring to the annular protrusion is equal to the distance between the first sealing plate and the second sealing plate.

[0018] Technical effects and advantages of the present invention:

[0019] 1. When a blowout occurs, the liquid in the well will be ejected from the wellhead simultaneously through the inner side of the inner tube and the annular gap between the inner tube and the outer tube. During this process, the sealing ring can move upward, thereby cooperating with the sealing groove on the sealing ring to seal the annular gap between the inner tube and the outer tube, and the first sealing plate can move upward and connect with the second sealing plate, so that the inner tube can be closed under the mutual cooperation of the first sealing plate and the second sealing plate, thereby avoiding the occurrence of a blowout accident;

[0020] 2. When connecting the inner tube and the outer tube, first align the multiple blocks outside the inner tube with the gaps between the multiple limit blocks on the inner wall of the outer tube one by one, then slowly insert the inner tube into the outer tube, and when the limit plate contacts the bottom groove wall of the limit groove, rotate the inner tube to drive the block and the card plate to slide along the top and bottom of the limit block respectively. When the block contacts the stopper on the limit block, stop rotating the inner tube. At this time, the inner tube and the outer tube can be connected together under the cooperation of the limit block, the card plate and the block, thereby realizing the quick connection of the outer tube and the inner tube. When the inner tube and the outer tube need to be separated, it is only necessary to rotate the inner tube in the opposite direction so that the limit block is rotated out from between the block and the card plate to realize the quick separation of the inner tube and the outer tube, thereby improving the assembly and disassembly efficiency of the inner tube and the outer tube.

[0021] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 is a three-dimensional schematic diagram of the present invention;

[0024] Figure 2 is a three-dimensional schematic diagram of the inner tube in the present invention;

[0025] Figure 3 is a three-dimensional schematic diagram of a part of the blowout preventer in the present invention;

[0026] Figure 4 is a three-dimensional sectional view of a part of the inner tube in the present invention;

[0027] Figure 5 is in the present invention Figure 4 enlarged view of part A;

[0028] Figure 6 is a connection schematic diagram of a part of the outer tube and a part of the inner tube in the present invention;

[0029] Figure 7 is a three-dimensional sectional view of a part of the outer tube in the present invention.

[0030] In the figure: 1. Outer tube; 2. Inner tube; 3. Limit block; 4. Stop block; 5. Connection device; 51. Clamping block; 52. Clamping plate; 6. Blowout preventer; 601. Sealing ring; 602. Annular protrusion; 603. Fixed rod; 604. Sealing tube; 605. First sealing plate; 606. Second sealing plate; 607. Insert block; 608. Telescopic block; 609. Positioning block; 610. Positioning hole; 611. Spring; 7. Limiting plate; 8. Limiting groove; 9. Roller shaft; 10. Sealing sleeve. Detailed implementation manners

[0031] To make the purposes, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] The present invention provides as Figures 1 - 7The double-wall drill pipe for oil drilling shown in the figure includes an outer pipe 1, an inner pipe 2 is inserted into the outer pipe 1. Along the up and down direction, two groups of limiting components are arranged on the inner wall of the outer pipe 1. The limiting components are composed of multiple limiting blocks 3, and the multiple limiting blocks 3 are evenly fixedly connected to the inner wall of the outer pipe 1. A stop block 4 is fixedly connected to the top of the limiting block 3. The stop block 4 is located at the front side position in the rotation direction of the outer pipe 1, and the rotation direction of the outer pipe 1 during operation is opposite to the rotation direction when the inner pipe 2 and the outer pipe 1 are connected. At the position on the outer wall of the inner pipe 2 opposite to the limiting components, a connecting device 5 matching the number of the limiting blocks 3 is provided. The connecting device 5 includes a clamping block 51, the clamping block 51 is fixedly connected to the outer wall of the inner pipe 2. A clamping plate 52 is provided at the bottom of the clamping block 51, the clamping plate 52 is fixedly connected to the outer wall of the inner pipe 2, and the distance between the clamping plate 52 and the clamping block 51 matches the height of the limiting block 3. An anti-blowout device 6 is provided at the position of the inner pipe 2 near the top. A plurality of limiting plates 7 are annularly distributed on the outer surface of the inner pipe 2 near the top, and the limiting plates 7 are fixedly connected to the outer wall of the inner pipe 2. An annular limiting groove 8 is opened at the position on the inner wall of the outer pipe 1 opposite to the plurality of limiting plates 7. The top groove wall of the limiting groove 8 is communicated with the top of the outer pipe 1, and the plurality of limiting plates 7 are slidably inserted into the limiting groove 8. The inner diameter of the top of the outer pipe 1 is the same as the outer diameter of the bottom of the outer pipe 1, and matching threads and screw threads are respectively provided on the inner wall of the top of the outer pipe 1 and the outer wall of the bottom of the outer pipe 1. The outer diameter of the bottom of the inner pipe 2 matches the inner diameter of the top of the inner pipe 2, and a sealing sleeve 10 is fixedly sleeved on the outer wall of the bottom of the inner pipe 2;

[0033] When connecting the inner pipe 2 and the outer pipe 1, first make the gaps between the multiple clamping blocks 51 outside the inner pipe 2 and the multiple limiting blocks 3 on the inner wall of the outer pipe 1 face each other one by one. Then slowly insert the inner pipe 2 into the outer pipe 1. When the limiting plate 7 contacts the bottom groove wall of the limiting groove 8, stop inserting the inner pipe 2. At this time, the limiting block 3 is exactly located between the clamping block 51 and the clamping plate 52. Then rotate the inner pipe 2 to make it drive the clamping block 51 and the clamping plate 52 to slide along the top and bottom of the limiting block 3 respectively. When the clamping block 51 contacts the stop block 4 on the limiting block 3, stop rotating the inner pipe 2. At this time, the inner pipe 2 and the outer pipe 1 can be connected together under the cooperation of the limiting block 3, the clamping plate 52 and the clamping block 51, thus realizing the rapid connection of the outer pipe 1 and the inner pipe 2. When it is necessary to separate the inner pipe 2 and the outer pipe 1, just rotate the inner pipe 2 in the reverse direction to make the limiting block 3 rotate out from between the clamping block 51 and the clamping plate 52, and the rapid separation of the inner pipe 2 and the outer pipe 1 can be realized, which improves the assembly and disassembly efficiency of the inner pipe 2 and the outer pipe 1;

[0034] When it is necessary to connect two outer pipes 1 and two inner pipes 2, the two outer pipes 1 can be connected together through the threads provided on the inner wall of their tops and the thread of the external thread on the outer wall of their bottoms, while the two inner pipes 2 can be inserted into each other. Since the sealing sleeve 10 is provided at the bottom of the inner pipe 2, when the two inner pipes 2 are connected, the sealing sleeve 10 can be inserted into the inner side of the top of the inner pipe 2 at the bottom along with the inner pipe 2 at the top, thereby increasing the sealing performance between the two inner pipes 2;

[0035] By providing the blowout preventer device 6, when a blowout occurs, the blowout preventer device 6 can simultaneously seal the gap between the inner pipe 2 and the outer pipe 1 and the inner side of the inner pipe 2, thereby achieving the closing effect on the wellhead and avoiding the occurrence of well kick accidents.

[0036] Such as Figures 2 - 6As shown, the blowout preventer 6 includes a sealing ring 601. The sealing ring 601 is located at the top of the limit plate 7 and is sleeved outside the inner tube 2. An annular protrusion 602 is provided on the top of the sealing ring 601. The annular protrusion 602 is fixedly sleeved on the outer wall of the inner tube 2, and a sealing groove matching the annular protrusion 602 is opened on the top of the sealing ring 601. Fixed rods 603 are fixedly connected to the inner walls on both sides of the sealing ring 601. A strip-shaped chute is vertically penetrated through the inner tube 2 at the corresponding position of the fixed rod 603, and the fixed rod 603 is inserted through the chute. The opposite ends of the two fixed rods 603 are fixedly connected to the same sealing tube 604, and the sealing tube 604 is slidably inserted into the inner tube 2. A first sealing plate 605 is fixedly connected to the inner side of the sealing tube 604 near the top position. The first sealing plate 605 is penetrated with a plurality of first through holes. A second sealing plate 606 is provided on the top of the first sealing plate 605. The second sealing plate 606 is fixedly connected to the inner wall of the inner tube 2. The second sealing plate 606 is penetrated with a plurality of second through holes, and the plurality of second through holes are staggered with the plurality of first through holes one by one. A plurality of insertion blocks 607 are fixedly connected to the bottom of the second sealing plate 606. The plurality of insertion blocks 607 correspond to and match the plurality of first through holes one by one. An L-shaped groove is opened on the bottom groove wall of the chute, and the horizontal section of the L-shaped groove is communicated with the inside of the inner tube 2. A telescopic block 608 is slidably inserted into the vertical section of the L-shaped groove. The top of the telescopic block 608 is fixedly connected to the bottom of the fixed rod 603. A positioning block 609 is slidably inserted into the horizontal section of the L-shaped groove. A positioning hole 610 is opened on the outer wall of the sealing tube 604 at the corresponding position of the positioning block 609. A spring 611 is connected between the end of the positioning block 609 away from the positioning hole 610 and the vertical section of the L-shaped groove. The contact positions of the telescopic block 608 and the positioning block 609 are both designed as inclined surfaces, and the projection lengths of the two in the vertical direction are greater than the distance between the free end of the positioning block 609 and the positioning hole 610 in the natural state. The outer diameter of the sealing ring 601 matches the inner diameter of the outer tube 1, and the distance from the sealing ring 601 to the annular protrusion 602 is equal to the distance between the first sealing plate 605 and the second sealing plate 606;

[0037] During normal use, the flushing medium impacts downward on the sealing ring 601 along the annular gap between the outer pipe 1 and the inner pipe 2. At this time, the sealing ring 601 separates from the annular protrusion 602 under the impact of the flushing medium, and the flushing medium can flow smoothly downward through the gap between the sealing ring 601 and the annular protrusion 602. Meanwhile, with the impact of the flushing medium on the sealing ring 601, the sealing ring 601 can drive the telescopic block 608 to move downward through the fixing rod 603. When the telescopic block 608 contacts the positioning block 609, the telescopic block 608 first gradually contracts. When the telescopic block 608 reaches the maximum contraction amount, the telescopic block 608 can squeeze the positioning block 609 through the inclined surface at its bottom, so that the positioning block 609 stretches the spring 611 and inserts into the positioning hole 610 on the sealing pipe 604 under the push of the telescopic block 608, thereby locking the sealing pipe 604. When the flushing medium flows upward out of the wellhead along the inner side of the inner pipe 2, since the sealing pipe 604 is locked by two positioning blocks 609, the sealing pipe 604 will not move when the flushing medium impacts on the bottom of the first sealing plate 605. Thus, it can be ensured that during normal use, the first sealing plate 605 will not be connected to the second sealing plate 606, and further ensure that the flushing medium can flow smoothly out of the wellhead along the inner pipe 2;

[0038] When a blowout occurs, the liquid in the well will spray out of the wellhead simultaneously through the inner side of the inner pipe 2 and the annular gap between the inner pipe 2 and the outer pipe 1. During this process, when the liquid impacts upward on the sealing ring 601 from bottom to top, the sealing ring 601 moves upward under the push of the liquid and is connected to the annular protrusion 602, and the annular protrusion 602 can cooperate with the sealing groove on the sealing ring 601 to seal the annular gap between the inner pipe 2 and the outer pipe 1;

[0039] Meanwhile, as the sealing ring 601 gradually moves upward, the telescopic block 608 also gradually moves upward and elongates under the drive of the fixing rod 603. With the separation of the telescopic block 608 from the positioning block 609, the positioning block can move out of the positioning hole 610 under the pull of the spring 611. At this time, the sealing pipe 604 is no longer restricted by the positioning block 609. Therefore, as the liquid impacts on the bottom of the first sealing plate 605, the first sealing plate 605 can gradually be connected to the second sealing plate 606. And when the two are connected together, the insertion block 607 on the second sealing plate 606 can seal the first through hole on the first sealing plate 605, so that the inner pipe 2 can be closed under the mutual cooperation of the first sealing plate 605 and the second sealing plate 606, thereby avoiding the occurrence of well kick accidents.

[0040] Such as Figure 2 、 Figure 4 and Figure 6As shown, the top views of the clamping block 51 and the clamping plate 52 are the same, and the width of the clamping block 51 is less than the distance between two adjacent limiting blocks 3. A plurality of roller shafts 9 are rotatably connected between the clamping block 51 and the clamping plate 52, and the roller shafts 9 are in close contact with the limiting blocks 3. The opposite sides of the clamping block 51 and the limiting block 3 are both designed with arc surfaces, and the radian of the arc surfaces of the two is the same and they are in fit with each other;

[0041] During the process of inserting the inner tube 2 into the outer tube 1, when the limiting plate 7 contacts the bottom wall of the limiting groove 8, stop inserting the inner tube 2. At this time, the limiting block 3 is exactly located between the clamping block 51 and the clamping plate 52. Then rotate the inner tube 2 to make it drive the clamping block 51 and the clamping plate 52 to slide along the top and bottom of the limiting block 3 respectively. During this process, as the inner tube 2 rotates, the roller can roll along the side surface of the limiting block 3, thereby reducing the friction between the inner tube 2 and the outer tube 1, and further facilitating the rapid connection of the inner tube 2 and the outer tube 1;

[0042] Since the opposite surfaces of the clamping block 51 and the limiting block 3 are both designed with arc surfaces, when the outer tube 1 and the inner tube 2 are connected together, the arc surfaces of the two can be in fit with each other and restrict each other, so that the axis of the inner tube 2 can coincide with the axis of the outer tube 1, thereby avoiding the shaking between the inner tube 2 and the outer tube 1 caused by the different axes of the two.

[0043] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A double-wall drill pipe for oil drilling, comprising an outer tube, characterized in that: an inner tube is inserted into the outer tube, two sets of limit assemblies are provided on the inner wall of the outer tube in the up and down directions, the limit assembly is composed of a plurality of limit blocks, and the plurality of limit blocks are evenly fixedly connected to the inner wall of the outer tube, and the top of the limit block is fixedly connected to a stopper, a connection device matching the number of limit blocks is provided at a position where the outer wall of the inner tube is opposite to the limit assembly, a blowout prevention device is provided near the top of the inner tube, a plurality of limit plates are distributed annularly on the outer surface of the inner tube near the top, the limit plates are fixedly connected to the outer wall of the inner tube, and the inner wall of the outer tube is provided with a plurality of limit plates. An annular limiting groove is provided at a position opposite to the multiple limiting plates, the top groove wall of the limiting groove is communicated with the top of the outer tube, and the multiple limiting plates are slidably inserted in the limiting groove, the blowout prevention device includes a sealing ring, the sealing ring is located at the top of the limiting plate, and the sealing ring is sleeved on the outside of the inner tube, the top of the sealing ring is provided with an annular protrusion, the annular protrusion is fixedly sleeved on the outer wall of the inner tube, and a sealing groove matching the annular protrusion is provided on the top of the sealing ring, fixing rods are fixedly connected to the inner walls on both sides of the sealing ring, and a strip-shaped sliding groove is provided on the inner tube corresponding to the fixing rod in the vertical direction, and the fixing rod The two fixing rods are inserted into the slide groove, and the opposite ends of the two fixing rods are fixedly connected to the same sealing tube, and the sealing tube is slidably inserted into the interior of the inner tube. A first sealing plate is fixedly connected to the inner side of the sealing tube near the top position, and the first sealing plate is penetrated by a plurality of first through holes. A second sealing plate is provided on the top of the first sealing plate, and the second sealing plate is fixedly connected to the inner wall of the inner tube. A plurality of second through holes are penetrated on the second sealing plate, and the plurality of second through holes are staggered one by one with the plurality of first through holes. A plurality of plug blocks are fixedly connected to the bottom of the second sealing plate, and the plurality of plug blocks correspond one to one with the plurality of first through holes. And they are matched, an L-shaped groove is provided on the bottom groove wall of the slide, and the horizontal section of the L-shaped groove is connected to the inside of the inner tube, the vertical section of the L-shaped groove is slidably connected with a telescopic block, the top of the telescopic block is fixedly connected to the bottom of the fixed rod, the horizontal section of the L-shaped groove is slidably connected with a positioning block, and a positioning hole is provided on the outer wall of the sealing tube at the corresponding position of the positioning block, and a spring is connected between the end of the positioning block away from the positioning hole and the vertical section of the L-shaped groove; the contact position between the telescopic block and the positioning block is a slope design, and the projection length of the two in the vertical direction is greater than the distance between the free end of the positioning block and the positioning hole in the natural state.

2. The double-wall drill pipe for oil drilling according to claim 1, characterized in that: The connecting device includes a card block, which is fixedly connected to the outer wall of the inner tube. A card plate is provided at the bottom of the card block, which is fixedly connected to the outer wall of the inner tube, and the distance between the card plate and the card block matches the height of the limit block.

3. The double-wall drill pipe for oil drilling according to claim 2, characterized in that: The top views of the card block and the card plate are the same, and the width of the card block is smaller than the distance between two adjacent limit blocks. A plurality of rollers are rotatably connected between the card block and the card plate, and the rollers are in close contact with the limit blocks.

4. The double-wall drill pipe for oil drilling according to claim 3, characterized in that: The opposite sides of the clamping block and the limiting block are both designed with arc surfaces, and the curvature of the two arc surfaces is the same and fits well.

5. The double-wall drill pipe for oil drilling according to claim 4, characterized in that: The inner diameter of the top of the outer tube is the same as the outer diameter of the bottom thereof, and mutually matching threads and thread teeth are respectively provided on the inner wall of the top of the outer tube and the outer wall of the bottom of the outer tube.

6. The double-wall drill pipe for oil drilling according to claim 5, characterized in that: The outer diameter of the bottom of the inner tube matches the inner diameter of the top thereof, and a sealing sleeve is fixedly sleeved on the outer wall of the bottom of the inner tube.

7. The double-wall drill pipe for oil drilling according to claim 6, characterized in that: The outer diameter of the sealing ring matches the inner diameter of the outer tube, and the distance from the sealing ring to the annular protrusion is equal to the distance between the first sealing plate and the second sealing plate.

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