A double-impregnated diamond bit continuous casing drilling tool system

Abstract

The invention relates to a double-impregnated diamond drill bit continuous casing drilling system, comprising an inner drill bit, an outer drill bit, a drill pipe, a casing joint and a casing. The inner drill bit is driven to rotate by the drill pipe and provides drilling pressure, and the outer drill bit is driven to rotate by the inner drill bit through a transmission key. The drilling pressure can be provided by the casing or by the drill pipe under the joint action of the inner and outer drill bit limits. The design of multiple pressure bearings and guide bearings can realize the function of independent rotation of the outer drill bit and its upper casing. The characteristic spiral grooves on the surface of the casing itself are conducive to the rotation and unblocking of the casing when the broken formation is stuck under the action of friction. The high carcass design of the inner and outer drill bits increases the drilling depth, thereby increasing the casing following depth and realizing continuous casing following drilling. At the same time, since drilling is not stopped during the drilling process, the casing continues to follow, and the friction between the casing and the hole wall is always dynamic friction, which can significantly reduce energy loss compared with the static friction generated when drilling is stopped.

Description

Technical Field

[0001] The invention belongs to the technical field of deep drilling construction, and in particular relates to a double-impregnated diamond drill bit continuous casing drilling tool system. Background Art

[0002] To improve the stability of the borehole wall and construction efficiency when drilling in broken formations such as gravel, casing drilling technology is usually used to maintain the stability of the borehole wall, which has obvious effects. At present, conventional casing drilling technology mainly involves down-the-hole hammer casing drilling in a gas environment. There are two methods: eccentric casing drilling and concentric casing drilling. Eccentric casing drilling uses the vibration and impact of the impactor in the drill bit assembly to drive the eccentric drill bit to drill the hole. During drilling, the eccentric drill bit is deflected outward due to the centrifugal force and friction on the eccentric drill bit, thereby achieving the purpose of expanding the hole diameter. The impact of the stabilizer in the drill bit assembly then drives the casing to follow. The rock cuttings generated inside the borehole are blown out of the hole through the keyway on the stabilizer by the air compressor. After drilling is complete, the eccentric wheel is reversed, retracting it into the casing and then withdrawing it from the casing. The casing remains in the hole to protect the wall and create a hole. Concentric follow-through drilling uses the center drill bit and the concentric sleeve surrounding the center drill bit to impact and crush the rock to create a hole. The concentric sleeve also uses the hole-expanding effect of the concentric sleeve to pull the casing into the hole. The concentric sleeve is equipped with a keyway. After reaching the bedrock, the center drill bit reverses and exits through the concentric sleeve. Concentric follow-through effectively solves the problems of drill sticking and rock drilling caused by complex geological conditions during eccentric follow-through drilling, facilitating construction operations and improving drilling efficiency.

[0003] However, these two conventional methods are only suitable for drilling shallower than 100 meters. As well depth increases, the friction between the casing and the wellbore increases due to the irregularities of the wellbore during percussive rotary drilling in a gaseous environment. This, combined with the fractured formation, can easily cause the drill to become stuck. This is particularly true for drilling in hot dry rock, where the wellbore is buried at depths exceeding 1,000 meters and is subject to significant thermal stress and sudden cooling, making cracking and sticking a problem. Therefore, existing percussive drilling techniques and processes are no longer sufficient for drilling deep wells in fractured formations.

[0004] To address these issues, it is necessary to develop a casing drilling system with wall protection in mud environments. Using a double-impregnated diamond drill bit, this can theoretically achieve continuous casing drilling in deep wells, including fractured and hot dry rock formations. Therefore, innovative research on a continuous casing drilling system with an impregnated diamond drill bit in mud environments is of great significance. Summary of the Invention

[0005] The present invention proposes a double-impregnated diamond drill bit continuous casing drilling system, which is intended to achieve deep well crushing and dry hot rock formation continuous casing drilling.

[0006] A double-impregnated diamond drill bit continuous casing drilling system, comprising an inner drill bit, an outer drill bit, a first transmission key, a second transmission key, an inner drill bit limiter, an outer drill bit limiter, a first copper sleeve, a second copper sleeve, an outer drill bit joint, an inner drill bit joint, a spring piece, an inner seal, an outer seal, a lower pressure bearing, a middle pressure bearing, an upper pressure bearing, a lower guide bearing limiter, an upper guide bearing limiter, a guide bearing, an outer drill bit joint limiter, a drill pipe, a casing joint, and a casing;

[0007] The inner drill bit is different from a conventional diamond-impregnated drill bit and has a specific structure. Its upper end is fixedly connected to the lower end of the inner drill bit joint, and the upper end of the inner drill bit joint is fixedly connected to the lower end of the drill rod. The outer side of the inner drill bit has N first key grooves evenly distributed circumferentially, N ≥ 1. The inner side of the inner drill bit limiter has N second key grooves evenly distributed circumferentially, N ≥ 1. N first transmission keys are fixed between the first key groove and the second key groove, N ≥ 1.

[0008] The outer drill bit is also different from conventional diamond-impregnated drill bits. It has a specific structure. The inner side of the outer drill bit has N third key slots evenly distributed along the circumference, N ≥ 1. The outer side of the outer drill bit limiter has N fourth key slots evenly distributed along the circumference, N ≥ 1. N second transmission keys are fixed between the third and fourth key slots.

[0009] The outer side of the inner drill bit limiter is circumferentially evenly distributed with N first protrusions, N ≥ 1, the inner side of the outer drill bit limiter is circumferentially evenly distributed with N second protrusions, N ≥ 1, and a first boss is provided on the inner bottom of the outer drill bit limiter. The inner drill bit limiter is coaxially rotatably connected to the outer drill bit limiter, and the first boss is limited at the upper end of the first boss. When the inner drill bit limiter rotates, the first boss and the second boss are in contact and engaged with each other, thereby realizing the rotation of the inner drill bit limiter and driving the circumferential rotation of the outer drill bit limiter.

[0010] The lower end of the outer drill bit joint is fixedly connected to the upper end of the outer drill bit, and a plurality of mud holes are evenly distributed on the outer drill bit joint in the circumferential direction and penetrate into the interior of the outer drill bit joint. The outer drill bit joint is also provided with a first threaded interface, a first groove and a second groove. The outer wall of the first copper sleeve is fixedly connected to the first threaded interface by a thread, the spring piece is arranged in the second groove, and the inner sealing member is arranged in the first groove. The lower end of the outer drill bit joint limiter is fixedly connected to the upper end of the outer drill bit joint, and the inner drill bit joint is fixedly connected to the second copper sleeve. The second copper sleeve is limited at the upper end of the first copper sleeve and the first copper sleeve and the second copper sleeve can rotate coaxially, thereby sealing the annular gap between the outer drill bit joint and the inner drill bit joint, and the inner diameter of the first copper sleeve is smaller than the outer diameter of the second copper sleeve;

[0011] The cam is fixedly provided with a third groove and a fourth groove on the sleeve joint, and the lower guide bearing limit and the upper guide bearing limit are fixedly connected to the sleeve joint, and the upper and lower ends of the inner ring of the guide bearing are respectively pressed on the upper end surface of the lower guide bearing limit and the lower end surface of the upper guide bearing limit, and the outer ring of the guide bearing is fixedly connected to the inner wall of the outer drill bit joint. The upper surface of the lower pressure bearing is tightly connected with the lower end surface of the lower guide bearing limit, and the lower surface of the lower pressure bearing is in close contact with the upper end surface of the spring sheet, the upper end of the inner seal is in close contact with the lower end surface of the sleeve joint, the lower surface of the middle pressure bearing is in close contact with the upper surface of the upper guide bearing limit, the upper surface of the middle pressure bearing is in close contact with the lower inner surface of the outer drill bit joint limit, the upper pressure bearing is installed in the third groove, and the lower surface of the upper pressure bearing is in close contact with the upper surface of the outer drill bit joint limit. The outer seal is installed in the fourth groove, and the outer seal is in close contact with the upper surface of the outer drill bit joint limit.

[0012] Furthermore, the outer surfaces of the casing and casing joint are processed with characteristic spiral groove structures. When the casing is stuck by broken rocks, the casing is driven to rotate by ground equipment, so that the casing can be rotated and unstuck by relying on the characteristic spiral groove structure on its own surface during rotation.

[0013] Furthermore, when the first protrusion on the outer side of the inner drill bit limiter contacts the second protrusion on the inner side of the outer drill bit limiter, the inner drill bit water outlet of the inner drill bit and the water outlet of the outer drill bit are aligned.

[0014] Furthermore, the mud circulation path during drilling is: flowing out from the inner drill bit, flowing through the inner drill bit water outlet and the outer drill bit water outlet at the bottom of the outer drill bit, entering the annular space formed by the outer drill bit and the hole wall, and finally passing through the mud hole on the outer drill bit joint, entering the annular space gap formed by the drill pipe and casing, completing the overall circulation.

[0015] Furthermore, the path of mud circulation during drilling is as follows: a portion of the mud flows out of the inner drill bit, flows through the inner drill bit nozzle and the outer drill bit nozzle at the bottom of the outer drill bit, enters the annular space formed by the outer drill bit and the hole wall, and finally enters the annular space formed by the drill pipe and casing through the mud hole on the outer drill bit joint;

[0016] The remaining part flows out from the inner drill bit, passes through the inner drill bit water outlet, enters the annular space formed by the inner drill bit and the outer drill bit, flows out through the outer drill bit water outlet on the upper part of the outer drill bit, enters the annular space formed by the outer drill bit and the hole wall, and finally passes through the mud hole on the outer drill bit joint and enters the annular space gap formed by the drill pipe and casing, completing the overall circulation.

[0017] Beneficial effects of the present invention:

[0018] 1. The diamond-impregnated double drill bit produces less rock chips when rotary drilling into broken rocks, which can effectively solve the problem of concentric follow-up drilling where the annular space between the inner and outer tube assemblies is blocked by large rock chips and cannot rotate normally;

[0019] 2. Combined with high-frequency, low-amplitude impact rock crushing, the disturbance to the wellbore wall is small, reducing the deep-level interference to the broken wellbore wall. The hole wall is more regular, the drill bit and casing rotate independently, and the probability of jamming is small. Even if jamming occurs, the wellbore wall is relatively regular and has weak wrapping ability on the casing, so the jamming degree is relatively low, which improves the jam-free capability of the drilling tool system.

[0020] 3. The inner drill bit is driven by the drill pipe, while the outer drill bit is driven by the inner drill bit via a transmission key. Both the inner and outer drill bits are impregnated with diamond. Compared with down-the-hole hammer drilling, they cause less disturbance to the wellbore wall during drilling, leaving the hole wall intact and with a low probability of sticking. The high-carcass design of the inner and outer drill bits can greatly increase the drilling depth, thereby increasing the depth of the casing, and achieving continuous casing drilling without stopping until the drill bit reaches the end of its life or the designed casing depth is reached.

[0021] 4. During continuous drilling, the casing and the hole wall always exhibit dynamic friction, and the energy loss is relatively small. The inner drill bit provides drilling pressure through the drill pipe, and the outer drill bit obtains drilling pressure through the casing and the interaction between the inner and outer drill bit limiters.

[0022] 5. The design of the pressure bearing and guide bearing in this mechanism enables the outer drill bit and the casing above it to rotate independently. The drill bit structure of the inner drill bit can effectively avoid the problem of localized false circulation of mud that occurs in high-carcass drill bits. It limits the mud circulation path, allowing the mud to reach the bottom of the hole smoothly. Combined with the outer drill bit, mud circulation is realized, completing the cooling of the drill bit and the removal of rock chips at the bottom of the hole.

[0023] 6. Based on the above design, the drilling tool system can achieve continuous casing drilling in deep fractured formations, effectively solving problems such as drill sticking, drill burial, and hole collapse caused by fractured deep well formations, significantly reducing energy loss, shortening drilling time, and improving drilling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is an overall cross-sectional view of the present invention.

[0025] Figure 2 It is a three-dimensional schematic diagram of the inner drill bit of the present invention.

[0026] Figure 3 It is a three-dimensional schematic diagram of the outer drill bit of the present invention.

[0027] Figure 4 It is a three-dimensional schematic diagram of the inner drill bit limit of the present invention.

[0028] Figure 5 It is a three-dimensional schematic diagram of the outer drill bit limit of the present invention.

[0029] Figure 6 It is a three-dimensional cross-sectional view of the outer drill bit joint of the present invention.

[0030] Figure 7 It is a three-dimensional cross-sectional view of the sleeve joint of the present invention.

[0031] Figure 8 It is an overall schematic diagram of the casing and casing joint of the present invention.

[0032] Figure 9 It is a schematic diagram of the pressure transmission and torque isolation principle of the present invention.

[0033] Figure 10 Schematic diagram of the mud circulation trajectory in the present invention.

[0034] Figure 11 It is a schematic diagram of the principle of alignment of inner and outer drill nozzles of the present invention. DETAILED DESCRIPTION

[0035] See also Figures 1 to 11 A double-impregnated diamond drill bit continuous casing drilling system includes an inner drill bit 1, an outer drill bit 2, a first transmission key 3, a second transmission key 4, an inner drill bit limiter 5, an outer drill bit limiter 6, a first copper sleeve 7, a second copper sleeve 8, an outer drill bit joint 9, an inner drill bit joint 10, a spring piece 11, an inner seal 12, an outer seal 13, a lower pressure bearing 14, a middle pressure bearing 15, an upper pressure bearing 16, a lower guide bearing limiter 17, an upper guide bearing limiter 18, a guide bearing 19, an outer drill bit joint limiter 20, a drill rod 21, a casing joint 22, and a casing 23; N herein is specifically described as 4;

[0036] The upper end of the inner drill bit 1 is fixedly connected to the lower end of the inner drill bit joint 10 via threads, and the upper end of the inner drill bit joint 10 is fixedly connected to the lower end of the drill rod 21 via threads. The outer side of the inner drill bit 1 has four first key grooves 101 evenly distributed around the circumference, and the inner side of the inner drill bit limiter 5 has four second key grooves 501 evenly distributed around the circumference. The first transmission key 3 is fixed between the first key grooves 101 and the second key grooves 501.

[0037] The inner side of the outer drill bit 2 has four third key grooves 201 evenly distributed in the circumferential direction, and the outer side of the outer drill bit limiter 6 has four fourth key grooves 601 evenly distributed in the circumferential direction. The second transmission key 4 is fixed between the third key groove 201 and the fourth key groove 601.

[0038] Four first protrusions 502 are evenly distributed circumferentially on the outer side of the inner drill bit limiter 5, and four second protrusions 602 are evenly distributed circumferentially on the inner side of the outer drill bit limiter 6. A first boss 603 is provided on the inner bottom of the outer drill bit limiter 6. The inner drill bit limiter 5 and the outer drill bit limiter 6 are coaxially rotatably connected, and the first protrusion 502 is limited at the upper end of the first boss 603. When the inner drill bit limiter 5 rotates, the first protrusion 502 and the second protrusion 602 come into contact and engage with each other, thereby realizing the rotation of the inner drill bit limiter 5 and driving the outer drill bit limiter 6 to rotate circumferentially.

[0039] The lower end of the outer drill bit joint 9 is fixedly connected to the upper end of the outer drill bit 2 by a thread. The outer drill bit joint 9 is circumferentially evenly distributed with several mud holes 901 that penetrate into the interior of the outer drill bit joint 9. The outer drill bit joint 9 is also provided with a first threaded interface 902, a first groove 903 and a second groove 904. The outer wall of the first copper sleeve 7 is fixedly connected to the first threaded interface 902 by a thread. The spring piece 11 is arranged in the second groove 904. Its function is to make the lower pressure bearing 14 better withstand pressure. The inner seal 12 is arranged in the first groove 903. The lower end of the inner and outer drill bit joint limiter 20 is fixedly connected to the upper end of the outer drill bit joint 9 by a thread, and the inner drill bit joint 10 is fixedly connected to the second copper sleeve 8 by a thread. The second copper sleeve 8 is limited to the upper end of the first copper sleeve 7 and the first copper sleeve 7 and the second copper sleeve 8 can rotate coaxially, similar to a mechanical seal structure. The main function is to seal the annular gap between the outer drill bit joint 9 and the inner drill bit joint 10. The inner diameter of the first copper sleeve 7 is smaller than the outer diameter of the second copper sleeve 8, so that the axial vertical downward translation movement of the second copper sleeve 8 is limited by the first copper sleeve 7;

[0040] The lower end of the sleeve 23 is fixedly connected to the upper end of the sleeve joint 22 by a thread. The sleeve joint 22 is provided with a third groove 221 and a fourth groove 222. The lower guide bearing limit 17 and the upper guide bearing limit 18 are fixedly connected to the sleeve joint 22 by a thread. The upper and lower ends of the inner ring of the guide bearing 19 are respectively pressed against the upper end surface of the lower guide bearing limit 17 and the lower end surface of the upper guide bearing limit 18. The outer ring of the guide bearing 19 is fixedly connected to the inner wall of the outer drill bit joint 9. The upper surface of the lower pressure bearing 14 is tightly connected to the lower end surface of the lower guide bearing limit 17. The lower surface of the lower pressure bearing 14 is tightly connected to the elastic The upper end surface of the sheet 11 is in close contact, the upper end of the inner seal 12 is in close contact with the lower end surface of the sleeve joint 22, the lower surface of the middle pressure bearing 15 is in close contact with the upper surface of the upper guide bearing limit 18, the upper surface of the middle pressure bearing 15 is in close contact with the inner lower surface of the outer drill bit joint limit 20, the upper pressure bearing 16 is installed in the third groove 221, and the lower surface of the upper pressure bearing 16 is in close contact with the outer upper surface of the outer drill bit joint limit 20, the outer seal 13 is installed in the fourth groove 222, and the outer seal 13 is in close contact with the outer upper surface of the outer drill bit joint limit 20.

[0041] Furthermore, combining Figure 8The outer surfaces of the casing 23 and the casing joint 22 are processed with a characteristic spiral groove structure 24; its function is: during actual drilling, if the casing 23 is stuck by broken rocks, the casing 23 can be driven by ground equipment so that the casing 23 can be rotated to unblock by relying on the characteristic spiral groove structure on its own surface during rotation.

[0042] Furthermore, the inner diameter of the first copper sleeve 7 is smaller than the outer diameter of the second copper sleeve 8, the inner diameter of the first copper sleeve 7 is larger than the outer diameter of the first transmission key 3, and the inner diameter of the first copper sleeve 7 is larger than the outer diameter of the first protrusion 502, so that the axial vertical downward translational movement of the second copper sleeve 8 is restricted by the first copper sleeve 7.

[0043] Furthermore, combining Figure 2 、 Figure 3 、 Figure 10 and Figure 11 The working layer structures of both the inner and outer drill bits in this mechanism utilize a specific high-carcass drill designed independently by the research team. The specific structural design of the working layer of inner drill bit 1 can be found in the patent "Ultra-High Working Layer Involute Gate Impregnated Diamond Drill Bit and Preparation Method thereof," patent application number CN202111097075.2; the specific structural design of the working layer of outer drill bit 2 can be found in the patent "Integrated Cutting Teeth Impregnated Diamond Drill Bit," patent application number CN201910991035.9. The steel body structure of the inner and outer drill bits differs from that of conventional diamond-impregnated drill bits. To accommodate the specific structure of the modified drilling tool system, the high carcass design of the inner and outer drill bits increases drilling depth, thereby increasing casing depth, enabling continuous drilling with casing until the end of the drill bit's life. In actual drilling, the carcass height design of the inner and outer drill bits is determined based on actual drilling requirements. The structural design of the inner drill bit 1 can effectively avoid the occurrence of localized false circulation of mud that occurs in high-carcass drill bits. At the same time, the inner drill bit 1 limits the mud flow path, allowing the mud to fully circulate at the outer drill bit 2. Based on the above design, no matter how high the carcass height of the inner and outer drill bits is, the mud will first be transported to the bottom of the borehole, cooling the drill bit and cleaning the rock cuttings at the bottom of the hole. The inner and outer drill bits cooperate with each other to achieve continuous drilling with the casing, without stopping until the drill bit life or drilling design requirements are met. This can greatly shorten the drilling time, save drilling costs, and reduce energy loss during the drilling process, thereby improving drilling efficiency.

[0044] Furthermore, combining Figure 4 、 Figure 5 and Figure 11The maximum outer diameter of the inner drill stop 5 is greater than the minimum inner diameter of the outer drill stop 6. In actual movement, the first protrusion 502 provided on the outer side of the inner drill stop 5 will be blocked by the first boss 603 provided on the inner side of the outer drill stop 6, thereby limiting its axial vertical downward translation movement; at the same time, the first protrusion 501 provided on the outer side of the inner drill stop 5 will be blocked by the second protrusion 602 provided on the inner side of the outer drill stop 6, thereby limiting its circumferential rotation movement, so that the inner drill stop 5 can only rotate within a certain angle range; Figure 11 As shown, when the first protrusion 502 on the outside of the inner drill stop 5 contacts the second protrusion 602 on the inside of the outer drill stop 6, the inner drill nozzle 102 of the inner drill bit 1 is aligned with the outer drill nozzle 202 of the outer drill bit 2. At this time, the rotation of the inner drill bit 1 will drive the rotation of the outer drill bit 2.

[0045] Furthermore, combining Figure 9 In region ② between the outer drill bit joint 9 and the casing joint 22, there are located a spring clip 11, an inner seal 12, an outer seal 13, a lower pressure bearing 14, a middle pressure bearing 15, an upper pressure bearing 16, a guide bearing 19, a lower guide bearing stop 17, and an upper guide bearing stop 18. Based on this design, the outer drill bit joint 9 in region ③ is subject to pressure P applied by the casing joint 22 and casing 23 in region ①. However, the casing joint 22 and casing 23 in region ① are not subject to the torque generated by the rotation of the outer drill bit joint 9 in region ③. In other words, the outer drill bit 2 and casing 23 are independent of each other. Casing 23 only provides drilling pressure for the outer drill bit 2, allowing it to perform rotary drilling and not apply rotary torque to casing 23. In the unlikely event that casing 23 becomes stuck in broken rock, surface equipment can be used to rotate casing 23 to unblock it without affecting the normal drilling process of the outer drill bit 2.

[0046] Furthermore, combining Figure 2 、 Figure 3 、 Figure 10 and Figure 11 , it can be seen from the figure that the mud circulation is divided into two paths:

[0047] The first scenario is that the fluid flows out from the inner drill bit 1, passes through the inner drill bit nozzle 102 and the outer drill bit nozzle 202 at the bottom of the outer drill bit 2, enters the annular space formed by the outer drill bit 2 and the hole wall, and finally passes through the mud hole 901 on the outer drill bit joint 9 and enters the annular space formed by the drill pipe 21 and the casing 23, completing the entire circulation.

[0048] The second situation is that because the outer drill bit nozzle 202 of the outer drill bit 2 has multiple layers, a portion of the mud flows out of the inner drill bit 1, flows through the inner drill bit nozzle 102 and the nozzle 202 at the bottom of the outer drill bit 2, enters the annular space formed by the outer drill bit 2 and the hole wall, and finally passes through the mud hole 901 on the outer drill bit joint 9 and enters the annular space formed by the drill pipe 21 and the casing 23;

[0049] The remaining part flows out from the inner drill bit 1, passes through the inner drill bit water inlet 102, enters the annulus formed by the inner drill bit 1 and the outer drill bit 2, flows out through the outer drill bit water inlet (202) on the upper part of the outer drill bit 2, enters the annular space formed by the outer drill bit 2 and the hole wall, and finally passes through the mud hole 901 on the outer drill bit joint 9, enters the annular space gap formed by the drill pipe 21 and the casing 23, completing the overall circulation.

[0050] Working principle of the present invention:

[0051] The present invention discloses a double-impregnated diamond drill bit continuous casing drilling system. The working layer structures of both the inner and outer drill bits utilize a specific high-carcass drill bit independently designed by the research team. The steel body is newly designed to meet the structural requirements of the drilling system. The inner drill bit 1 is driven to rotate by the drill rod 21, and the outer drill bit 2 is driven to rotate by the inner drill bit 1 through the first transmission key 3 and the second transmission key 4. The inner drill bit 1 provides drilling pressure through the drill rod 21, and the outer drill bit 2 provides drilling pressure through the casing 23 and the drill rod 21. The design of the pressure bearing and guide bearing in this mechanism enables the outer drill bit 2 and the casing 23 above it to rotate independently. The drill bit structure used by the inner drill bit 1 can effectively avoid the problem of local mud false circulation that exists in high-carcass drill bits, limit the mud circulation path, and enable the mud to reach the bottom of the hole. In combination with the outer drill bit 2, mud circulation is achieved, completing the cooling of the drill bit and the cleaning of rock cuttings at the bottom of the hole. During the actual drilling process, the use of diamond-impregnated drill bits in both the inner and outer drill bits creates minimal disturbance to the wellbore wall, resulting in a relatively regular borehole surface. This, combined with the high-carcass design, significantly increases drilling depth, thereby increasing the depth of the casing, enabling continuous casing drilling until the bit life or drilling design requirements are met. Furthermore, since drilling continues without interruption, the casing can rotate independently and continue to follow the borehole. The friction between the casing and the borehole wall is always dynamic friction, which significantly reduces energy loss, shortens drilling time, and improves drilling efficiency compared to static friction generated when drilling is stopped.

Claims

1. A double-impregnated diamond drill bit continuous casing drilling system, characterized by: The drill bit comprises an inner drill bit (1), an outer drill bit (2), a first transmission key (3), a second transmission key (4), an inner drill bit limiter (5), an outer drill bit limiter (6), a first copper sleeve (7), a second copper sleeve (8), an outer drill bit joint (9), an inner drill bit joint (10), a spring piece (11), an inner seal (12), an outer seal (13), a lower pressure bearing (14), a middle pressure bearing (15), an upper pressure bearing (16), a lower guide bearing limiter (17), an upper guide bearing limiter (18), a guide bearing (19), an outer drill bit joint limiter (20), a drill rod (21), a casing joint (22) and a casing (23); The upper end of the inner drill bit (1) is fixedly connected to the lower end of the inner drill bit joint (10), and the upper end of the inner drill bit joint (10) is fixedly connected to the lower end of the drill rod (21). The outer side of the inner drill bit (1) is uniformly distributed with N first key grooves (101), N ≥ 1. The inner side of the inner drill bit limiter (5) is uniformly distributed with N second key grooves (501), N ≥ 1. N first transmission keys (3) are fixed between the first key groove (101) and the second key groove (501), N ≥ 1. The inner side of the outer drill bit (2) is uniformly distributed with N third key grooves (201), N ≥ 1; the outer side of the outer drill bit limiter (6) is uniformly distributed with N fourth key grooves (601), N ≥ 1; N second transmission keys (4) are fixed between the third key groove (201) and the fourth key groove (601); The outer side of the inner drill bit limiter (5) is uniformly distributed with N first protrusions (502) in the circumferential direction, N≥1; the inner side of the outer drill bit limiter (6) is uniformly distributed with N second protrusions (602) in the circumferential direction, N≥1; and the inner bottom of the outer drill bit limiter (6) is provided with a first boss (603); the inner drill bit limiter (5) and the outer drill bit limiter (6) are coaxially connected for rotation, and the first protrusion (502) is limited at the upper end of the first boss (603); when the inner drill bit limiter (5) rotates, the first protrusion (502) and the second protrusion (602) are in contact and engaged with each other, so that the inner drill bit limiter (5) rotates and then drives the outer drill bit limiter (6) to rotate circumferentially; The lower end of the outer drill bit joint (9) is fixedly connected to the upper end of the outer drill bit (2). The outer drill bit joint (9) is evenly distributed in an annular direction with a plurality of mud holes (901) penetrating into the interior of the outer drill bit joint (9). The outer drill bit joint (9) is also provided with a first threaded interface (902), a first groove (903) and a second groove (904). The outer wall of the first copper sleeve (7) is fixedly connected to the first threaded interface (902) through a thread. The spring piece (11) is provided in the second groove (904). The inner seal (12) is arranged in the first groove (903), the lower end of the outer drill bit joint limiter (20) is fixedly connected to the upper end of the outer drill bit joint (9), the inner drill bit joint (10) is fixedly connected to the second copper sleeve (8), the second copper sleeve (8) is limited at the upper end of the first copper sleeve (7), and the first copper sleeve (7) and the second copper sleeve (8) can rotate coaxially, thereby sealing the annular gap between the outer drill bit joint (9) and the inner drill bit joint (10), and the inner diameter of the first copper sleeve (7) is smaller than the outer diameter of the second copper sleeve (8); The lower end of the sleeve (23) is fixedly connected to the upper end of the sleeve joint (22), and the sleeve joint (22) is provided with a third groove (221) and a fourth groove (222). The lower guide bearing limiter (17) and the upper guide bearing limiter (18) are fixedly connected to the sleeve joint (22). The upper and lower ends of the inner ring of the guide bearing (19) are respectively pressed against the upper end surface of the lower guide bearing limiter (17) and the lower end surface of the upper guide bearing limiter (18). The outer ring of the guide bearing (19) is fixedly connected to the inner wall of the outer drill bit joint (9). The upper surface of the lower pressure bearing (14) is tightly connected to the lower end surface of the lower guide bearing limiter (17). The lower surface of the lower pressure bearing (14) is tightly connected to the spring (1 1) The upper end surface is in close contact, the upper end of the inner seal (12) is in close contact with the lower end surface of the sleeve joint (22), the lower surface of the middle pressure bearing (15) is in close contact with the upper surface of the upper guide bearing limit (18), the upper surface of the middle pressure bearing (15) is in close contact with the lower inner surface of the outer drill bit joint limit (20), the upper pressure bearing (16) is installed in the third groove (221), and the lower surface of the upper pressure bearing (16) is in close contact with the outer upper surface of the outer drill bit joint limit (20), the outer seal (13) is installed in the fourth groove (222), and the outer seal (13) is in close contact with the outer upper surface of the outer drill bit joint limit (20).

2. The double-impregnated diamond drill bit continuous casing drilling system according to claim 1, characterized in that: The outer surfaces of the casing (23) and the casing joint (22) are processed with a characteristic thread groove structure (24). When the casing (23) is stuck by broken rocks, the casing (23) is driven by ground equipment so that the casing (23) can be rotated and unstuck by relying on the characteristic thread groove structure (24) on its own surface during rotation.

3. The double-impregnated diamond drill bit continuous casing drilling system according to claim 1, characterized in that: When the first protrusion (502) on the outside of the inner drill bit limiter (5) contacts the second protrusion (602) on the inside of the outer drill bit limiter (6), the inner drill bit water outlet (102) of the inner drill bit (1) and the outer drill bit water outlet (202) of the outer drill bit (2) are in an aligned relationship.

4. The double-impregnated diamond drill bit continuous casing drilling system according to claim 1, characterized in that: The path of mud circulation during drilling is as follows: it flows out from the inner drill bit (1), flows through the inner drill bit water inlet (102) and the outer drill bit water inlet (202) at the bottom of the outer drill bit (2), enters the annular space formed by the outer drill bit (2) and the hole wall, and finally passes through the mud hole (901) on the outer drill bit joint (9) and enters the annular space formed by the drill rod (21) and the casing (23), completing the overall circulation.

5. The double-impregnated diamond drill bit continuous casing drilling system according to claim 1, characterized in that: The path of mud circulation during drilling is as follows: a portion of the mud flows out of the inner drill bit (1), flows through the inner drill bit water inlet (102) and the outer drill bit water inlet (202) at the bottom of the outer drill bit (2), enters the annular space formed by the outer drill bit (2) and the hole wall, and finally passes through the mud hole (901) on the outer drill bit joint (9) and enters the annular space formed by the drill pipe (21) and the casing (23); The remaining part flows out from the inner drill bit (1), passes through the inner drill bit water inlet (102), enters the annulus formed by the inner drill bit (1) and the outer drill bit (2), flows out through the outer drill bit water inlet (202) on the upper part of the outer drill bit (2), enters the annular space formed by the outer drill bit (2) and the hole wall, and finally passes through the mud hole (901) on the outer drill bit joint (9) and enters the annular space formed by the drill pipe (21) and the casing (23), completing the overall circulation.

6. A double-impregnated diamond drill bit continuous casing drilling system according to any one of claims 1 to 5, characterized in that: The inner drill bit (1) is a super-high working layer involute nozzle impregnated diamond drill bit.

7. A double-impregnated diamond drill bit continuous casing drilling system according to any one of claims 1 to 5, characterized in that: The outer drill bit (2) is an integrated cutting tooth impregnated diamond drill bit.

Images