A high reliability flexible drill rod

Abstract

A high-reliability flexible drill pipe includes a plurality of transmission units connected end to end, wherein the transmission unit includes a drill collar housing, a mandrel, a drilling pressure transmission structure and a torque transmission structure, wherein the drilling pressure transmission structure and the torque transmission structure are independently arranged to realize the separate transmission of drilling pressure and torque of a directional drilling tool, respectively, and the structure is simple and the development cost of a multi-layer oil field is greatly reduced. Since the centers of the drilling pressure transmission structure and the torque transmission structure coincide with each other, the length of the transmission unit can be shortened to the greatest extent during design, thereby facilitating the realization of the requirements of short-radius and ultra-short-radius drilling, realizing rotary directional drilling with a high build-up rate, and reducing the difficulty of well inclination control during rotary drilling, thereby increasing the reliability and build-up stability of the equipment.

Description

Technical Field

[0001] The invention relates to the technical field of oil exploitation and drilling, in particular to a high-reliability flexible drill rod. Background Art

[0002] In view of the needs of transformation of old oil fields, multi-layer oil fields and other formations, the economic efficiency of using traditional branch drilling or infill drilling is getting worse and worse. How to use drilling means to improve the contact effect between the wellbore and the formation, improve the oil field development effect, and reduce the development cost has become an important issue. In the current oil extraction industry, the short-radius branch wells or ultra-short-radius branch wells implemented have many disadvantages such as high cost, long drilling cycle, and unclear effect. In particular, the ultra-short radius drilling technology with a turning radius of less than 10 meters has gradually become an effective means to improve the contact degree of the formation. At present, the existing flexible drill pipe and high-pressure hose are means to achieve short-radius drilling. However, in the prior art, the flexible drill pipe can transmit the drilling pressure torque through the universal joint series it contains. The universal joint is mostly composed of an articulated structure and a torque transmission structure, and the torque is transmitted through a slot-key structure. Since the torque transmission structure is arranged on the contact surface of the articulated structure, when the flexible drill pipe passes through the high curvature well section, the slot and key of the torque transmission structure are seriously misaligned, which is easy to cause vibration and extremely easy to break. The process of using high-pressure hoses to achieve extremely short radius drilling is limited by their structure and cannot transmit torque or drilling pressure. In addition, high-pressure hoses can only drive water jet drills to break up the formation by jet drilling, and the wellbore diameter is about 1 inch, making it difficult to achieve good production capacity. Summary of the invention

[0003] In view of the above problems, the present invention provides a high-reliability flexible drill pipe, which realizes the transmission of drilling pressure and torque respectively through the independent drilling pressure transmission structure and torque transmission structure arranged between the drill collar shell and the core shaft. Compared with the solution of simultaneously transmitting drilling pressure and torque through a universal joint in the prior art, the size of the drilling pressure transmission structure and the torque transmission structure are reduced, and the wear of the drilling pressure transmission structure and the torque transmission structure are reduced, thereby improving the reliability of the drilling pressure transmission structure and the torque transmission structure. At the same time, the drill collar shell and the core shaft are protected from erosion and damage by the drilling circulating medium through an axial flexible jumper tube, and the coaxial characteristics of adjacent driven drill pipes can be maintained to a certain extent, thereby increasing the reliability of the equipment and the stability of transmitting drilling pressure and torque in high-curvature wellbores.

[0004] The technical solution of the present invention is as follows:

[0005] A high-reliability flexible drill pipe, comprising a plurality of transmission units connected end to end, the transmission unit comprising a drill collar shell, a mandrel, a drilling pressure transmission structure and a torque transmission structure, one end of the drilling pressure transmission structure is fixed to the drill collar shell, and the other end is fixed to the mandrel; the drilling pressure and axial tension between the drill collar shell and the mandrel are directly transmitted through the drilling pressure transmission structure; one end of the torque transmission structure is fixed to the drill collar shell, and the other end is fixed to the mandrel; the torque between the drill collar shell and the mandrel is directly transmitted through the torque transmission structure; the mandrel of each transmission unit can be axially deflected relative to its drill collar shell;

[0006] The drilling pressure transmission structure is independently arranged from the torque transmission structure, and when the core shaft of each transmission unit undergoes axial deflection relative to its drill collar shell, the deflection centers of the drilling pressure transmission structure and the torque transmission structure coincide with each other; one end of the core shaft extends out of the drill collar shell and is fixedly connected to the drill collar shell of an adjacent transmission unit, or the core shaft and the drill collar shell of an adjacent transmission unit are designed as an integrated structure to realize the transmission of drilling pressure and torque between adjacent transmission units.

[0007] Preferably, the distance from the torque transmission point, torque transmission line or torque transmission surface of the torque transmission structure to the deflection center is less than the minimum distance from the drilling pressure transmission surface of the drilling pressure transmission structure to the deflection center. That is, the structure of the torque transmission structure that realizes torque transmission can be torque transmission points, torque transmission lines or torque transmission surfaces arranged in pairs.

[0008] It should be noted that, in order to ensure that the distance from the torque transmission point, torque transmission line or torque transmission surface of the structure to the deflection center is less than the distance from the drilling pressure transmission surface to the deflection center, the drilling pressure transmission structure can be separately arranged away from the torque transmission structure, and the specific arrangement method is that the mandrel and the torque transmission structure are seated inside the drill collar shell through the inner sleeve of the drilling pressure transmission structure. Since the force is mutual, the torque input end and the torque output end of the torque transmission structure are mutually converted within the protection scope of the present invention, and the drilling pressure input end and the drilling pressure output end of the drilling pressure transmission structure are interchanged within the protection scope of the present invention.

[0009] Preferably, the drilling pressure transmission structure includes at least a first sliding surface group for bearing axial pressure, the first sliding surface group includes a first sliding surface fixed to the drill collar shell and a second sliding surface fixed to the core shaft, the first sliding surface and the second sliding surface are arc surfaces, the first sliding surface and the second sliding surface fit each other and can slide relative to each other with the deflection center of the drill collar shell and the core shaft as the center, so that when the axes of the drill collar shell and the core shaft are deflected, the direction of axial pressure transmission can be deflected without loss or with low loss.

[0010] The drilling pressure transmission structure also includes a second sliding surface group for bearing axial tension, the second sliding surface group includes a third sliding surface fixed to the core shaft and a fourth sliding surface fixed to the drill collar shell, the third sliding surface and the fourth sliding surface are arc surfaces, the third sliding surface and the fourth sliding surface fit each other and can slide relative to each other with the deflection center of the drill collar shell and the core shaft as the center, so that when the axis of the drill collar shell and the core shaft deflects, the direction of axial tension transmission can be deflected without loss or with low loss.

[0011] Preferably, in particular, when the drilling pressure transmission structure is arranged on the front and rear sides of the torque transmission structure, the core shaft and the torque transmission structure are seated inside the drill collar shell through the inner sleeve of the drilling pressure transmission structure, and the transmission unit at least includes a front sliding plate group and a rear sliding plate group, the front sliding plate group is arranged at the front end of the torque transmission structure, and the rear sliding plate group is arranged at the rear end of the torque transmission structure; the front sliding plate group and the rear sliding plate group both include an outer fixed plate and an inner fixed plate, the outer fixed plate is fixed on the drill collar shell, and the inner fixed plate is fixed on the core shaft; the first sliding surface and the second sliding surface are respectively the facing fitting surfaces of the inner fixed plate and the outer fixed plate of the rear sliding plate group; the third sliding surface and the fourth sliding surface are respectively the facing fitting surfaces of the outer fixed plate and the inner fixed plate of the front sliding plate group. Its unique advantage is that the drilling pressure transmission structure is arranged on the front and rear sides of the torque transmission structure, and the friction forces generated by the front sliding disc group and the rear sliding disc group can offset each other, which is not easy to cause structural dislocation, and can greatly extend the service life of the drilling pressure transmission structure and the torque transmission structure.

[0012] Preferably, when the drilling pressure transmission structure is arranged on either the front side or the rear side of the torque transmission structure, the transmission unit includes a first sliding plate, a second sliding plate and a spherical sliding plate, the spherical sliding plate is fixed on the core shaft, the second sliding surface and the third sliding surface are the front surface and the rear surface of the spherical sliding plate respectively; the first sliding plate is fixed to the drill collar shell and the first sliding surface is arranged on the rear surface of the first sliding plate, the second sliding plate is fixed to the drill collar shell and the fourth sliding surface is arranged on the front surface of the second sliding plate, and the first sliding plate, the second sliding plate and the spherical sliding plate all slide around the deflection center of the drill collar shell and the core shaft.

[0013] It should be noted that the torque transmission structure can be arranged away from the drilling pressure transmission structure or can be arranged to wrap each other, but no matter which arrangement is used, the deflection centers between the two always coincide, and the distance between each drilling pressure transmission sliding surface and the deflection center is always not less than the distance from the torque transmission point to the deflection center. Each drilling pressure transmission sliding surface can be fixed on the drill collar shell or the mandrel, and the distance between the drilling pressure transmission front sliding surface and the rear sliding surface from the deflection center can be equal or unequal, but no matter which arrangement is used, the lubrication gap between each set of sliding surfaces is smaller than the active gap of the torque transmission ball.

[0014] Preferably, the torque transmission structure includes a constant velocity universal joint, the input end of the constant velocity universal joint is fixed to the core shaft or the core shaft is the input end of the constant velocity universal joint; the output end of the constant velocity universal joint is fixed to the drill collar housing or the drill collar housing is the output end of the constant velocity universal joint.

[0015] Preferably, the torque transmission structure includes a ball cage type torque transmission structure, which is a ball cage type constant velocity universal joint, including multiple pairs of torque transmission balls and torque transmission balls moving in the ball groove, the length of the ball groove is greater than the diameter of the torque transmission ball, so that the torque transmission ball can produce spatial shaking in the ball groove, and when the axis of the core shaft and the drill shank shell is deflected, within the deflection limit range, the torque transmission ball will not get stuck at the edge of the ball groove.

[0016] Preferably, the distance from the center of each of the torque transmission balls to the center of the constant velocity joint is equal and smaller than the distance from the first pair of sliding surfaces and the second pair of sliding surfaces to the center of the constant velocity joint.

[0017] Preferably, the constant velocity universal joint comprises a tooth-groove type torque transmission structure; the tooth-groove type torque transmission structure comprises at least a first tooth groove and a second tooth groove, the first tooth groove and the second tooth groove are respectively a torque transmission tooth groove at the mandrel end and a torque transmission tooth groove at the shell end that can cooperate with each other to transmit torque, the mandrel end torque transmission tooth groove is fixedly connected to the mandrel, and the shell end torque transmission tooth groove is fixedly connected to the drill collar shell, so that torque can be transmitted between the drill collar shell and the mandrel through the teeth or keyways. The tooth grooves include teeth, keyways, and tooth grooves.

[0018] Preferably, the gap between the sliding surfaces of the first sliding surface group and / or the second sliding surface group is less than 1 mm.

[0019] Preferably, the maximum deflection angle that can be generated by the axis of the mandrel relative to the axis of the drill collar housing does not exceed 8°.

[0020] Preferably, an axial gap exists between the core shaft and the core shaft of the adjacent transmission unit to facilitate axial deflection of the core shaft relative to the drill collar housing; and at least at the position where the axial gap exists, the core shaft and the core shaft of the adjacent transmission unit are sealed and connected by an axial flexible jumper tube, and the axial flexible jumper tube is arranged in the through structure, and the axial flexible jumper tube is a high plastic material tube, a rubber tube, or a metal bellows.

[0021] Preferably, the axially flexible jumper tube runs through the main channel and connects all the transmission units in series. The axially flexible jumper tube is a high plastic material tube, a rubber tube, or a metal bellows.

[0022] A high-reliability flexible drilling system comprises the high-reliability flexible drill pipe, and also comprises an elastic seal and / or a dynamic sealing surface, wherein a sealed space is formed between the elastic seal and / or the dynamic sealing surface and the axial flexible jumper tube, and the sealed space is filled with a lubricating fluid for lubricating the transmission unit.

[0023] The advantages of the present invention over the prior art are as follows: the high-reliability flexible drill pipe of the present invention realizes the separate transmission of drilling pressure and torque of the directional drilling tool through the drilling pressure transmission structure and torque transmission structure independently arranged between the drill collar shell and the core shaft, and has a simple structure, safety and reliability. Since the centers of the drilling pressure transmission structure and the torque transmission structure coincide with each other, the length of the transmission unit can be shortened to the greatest extent during design, thereby meeting the requirements of short radius and ultra-short radius drilling, and increasing the reliability and inclination stability of the equipment. The drill collar shell and the core shaft are protected from erosion and damage by the drilling circulating medium through the axial flexible jumper tube, and at the same time, the coaxial characteristics of adjacent transmission units can be maintained to a certain extent, further improving the drilling stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic cross-sectional structural diagram of embodiment 1 of the high-reliability flexible drill rod of the present invention;

[0025] Figure 2 This is a schematic cross-sectional structure diagram of Embodiment 2 of the high-reliability flexible drill rod of the present invention;

[0026] Figure 3 yes Figure 2 A schematic diagram of the cross-sectional structure of the high-reliability flexible drill pipe when being deflected;

[0027] Figure 4 is a schematic cross-sectional structural diagram of embodiment 3 of the high-reliability flexible drilling tool of the present invention;

[0028] Figure 5 It is a schematic cross-sectional structure diagram of embodiment 4 of the high-reliability flexible drilling tool described in the present invention.

[0029] The reference numerals are as follows:

[0030] 1—transmission unit, 11—drill collar housing, 111—ball seat, 12—mandrel, 121—through structure, 13—drill pressure transmission structure, 131—first sliding surface group, 1311—first sliding surface, 1312—second sliding surface, 132—second sliding surface group, 1321—third sliding surface, 1322—fourth sliding surface, 14—torque transmission structure, 141—torsion ball, 142—ball groove, 143—tooth groove, 1431—torque transmission tooth groove at the mandrel end, 1432—torque transmission tooth groove at the housing end, 15—first sliding disk, 16 —Second sliding disk, 17—spherical sliding disk, 18—front sliding disk group, 181—inner fixed disk of the front sliding disk group, 182—outer fixed disk of the front sliding disk group, 19—rear sliding disk group, 191—outer fixed disk of the rear sliding disk group, 192—inner fixed disk of the rear sliding disk group, 2—adjacent transmission units, 21—drill collar housing of adjacent transmission units, 22—core shaft of adjacent transmission units, 3—electrical circuit, 4—axial gap, 5—axial flexible jumper tube, 6—elastic seal, 7—dynamic sealing surface, 8—other drilling units, 9—conductive slip ring. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention is described in more detail below in conjunction with the accompanying drawings and specific embodiments. The front and back described in the present invention are set based on the installation position of the drill bit, with the direction toward the drill bit being the front and the direction away from the drill bit being the back. The fixing described in the present invention includes but is not limited to adhesive fixing, keyway fixing, mortise and tenon structure fixing, welding fixing, and one-piece molding structure, based on meeting the mechanical requirements of use, so as to facilitate assembly.

[0032] Example 1

[0033] A high reliability flexible drill pipe, such as Figure 1-3As shown, it includes a plurality of transmission units 1 connected end to end, each transmission unit 1 includes a drill collar shell 11, a mandrel 12, and a drilling pressure transmission structure 13 and a torque transmission structure 14 arranged between the drill collar shell 11 and the mandrel 12, the drilling pressure transmission structure 13 and the torque transmission structure 14 are independently arranged and the deflection centers coincide with each other, so that when the drill collar shell 11 deflects relative to the mandrel 12, the drilling pressure transmission structure 13 can directly transmit the axial drilling pressure from the drill collar shell 11 to the mandrel 12. The drill collar shell 11 and the core shaft 12 are deflected, and the torque generated between the drill collar shell 11 and the core shaft 12 can be directly transmitted by the torque transmission structure 14 when the high-reliability flexible drill pipe rotates circumferentially, without transmitting the torque to the drilling pressure transmission surface (such as the first sliding surface group and / or the second sliding surface group) of the drilling pressure transmission structure 13. That is, the drilling pressure and torque of each transmission unit 1 can be independently transmitted through the drilling pressure transmission structure 13 and the torque transmission structure 14, respectively, and the torque force point of the torque transmission structure 14 does not bear the drilling pressure, so it will not generate periodic vibration, and will not break due to excessive pressure. One end of the mandrel 12 extends out of the drill collar housing 11 and is fixedly connected to the drill collar housing 21 of the adjacent transmission unit, or the mandrel 12 and the drill collar housing 21 of the adjacent transmission unit are designed as an integrated structure to achieve the transmission of drilling pressure and torque between adjacent transmission units.

[0034] During drilling, the transmission unit 1 may deflect relative to the adjacent transmission unit 2 as the curvature of the wellbore changes, and the high-reliability flexible drill pipe as a whole will also rotate to drive the drill bit to rotate and achieve drilling. Therefore, the torque transmission here includes the torque generated by the axis deflection between the drill collar housing 11 and the mandrel 12 and the torque generated by driving the drill bit to rotate and drill.

[0035] In this embodiment, the mandrel 12 and the torque transmission structure 14 are sleeved by the drilling pressure transmission structure 13 and seated inside the drill collar shell 11. The drilling pressure transmission structure 13 is arranged in front of the torque transmission structure 14 and the deflection centers coincide with each other.

[0036] The axial pressure (i.e., drilling pressure) and tension (without passing through the torque transmission structure 14) between the drill collar shell 11 and the mandrel 12 are directly transmitted through the drilling pressure transmission structure 13, and the torque (including the torque generated by axial deflection and circumferential rotation) between the drill collar shell 11 and the mandrel 12 is directly transmitted through the torque transmission structure 14 (without passing through the drilling pressure transmission structure 13); the drilling pressure and torque of the highly reliable flexible drill rod are transmitted separately, and the structure is simple, safe and reliable. And because the centers of the drilling pressure transmission structure 13 and the torque transmission structure 14 coincide with each other, the length of the transmission unit can be shortened to the greatest extent during design, thereby facilitating the realization of the requirements of short radius and ultra-short radius drilling.

[0037] like Figure 1-3 As shown, the drilling pressure transmission structure 13 at least includes a first sliding surface group 131 for bearing axial pressure, and the first sliding surface group 131 includes a first sliding surface 1311 fixed to the drill collar shell 11 and a second sliding surface 1312 fixed to the core shaft 12. The first sliding surface 1311 and the second sliding surface 1312 fit each other and can slide relative to each other around the center of the drilling pressure transmission structure 13, so that when the axes of the drill collar shell 11 and the core shaft 12 are deflected, the direction of transmission of axial pressure (such as drilling pressure and the gravity of the transmission unit itself) can be deflected without loss or with low loss, thereby transmitting the axial force without passing through the torque generating surface of the torque transmission structure 14.

[0038] Preferably, the WOB transmission structure 13 may also include a second sliding surface group 132 for bearing axial tension (such as the weight of the transmission unit and drill bit connected in front thereof), the second sliding surface group 132 includes a third sliding surface 1321 fixed to the mandrel 12 and a fourth sliding surface 1322 fixed to the drill collar shell 11, the third sliding surface 1321 and the fourth sliding surface 1322 are mutually fitted and can slide relative to each other around the deflection center of the WOB transmission structure 13, so that when the axis of the drill collar shell 11 and the mandrel 12 deflects, the direction of axial tension transmission can be deflected without loss or with low loss. Preferably, the first sliding surface group 131 can also be used to bear axial pressure, and correspondingly, the second sliding surface group 132 can also bear axial tension.

[0039] like Figure 1 As shown, this embodiment specifically provides the specific structure of the drilling pressure transmission structure 13:

[0040] The input end (front end) of the torque transmission structure 14 is provided with a front sliding disc set 18, and the output end (rear end) of the torque transmission structure 14 is provided with a rear sliding disc set 19, and vice versa. That is, the torque transmission structure 14 is wrapped inside the drilling pressure transmission structure 13, and the deflection center of the drilling pressure transmission structure 13 coincides with the deflection center of the torque transmission structure 14, so as to further shorten the length of the transmission unit 1 and achieve a higher deflection rate.

[0041] That is Figure 1 As shown, when the drilling pressure transmission structure is arranged on the front and rear sides of the torque transmission structure, the core shaft 12 and the torque transmission structure are seated inside the drill collar shell 11 through the inner sleeve of the drilling pressure transmission structure, and the transmission unit at least includes a front sliding disk group 18 and a rear sliding disk group 19, the front sliding disk group 18 is arranged at the input end of the torque transmission structure, and the rear sliding disk group is arranged at the front end of the torque transmission structure; the front sliding disk group and the rear sliding disk group both include an outer fixed disk and an inner fixed disk, the outer fixed disk is fixed on the drill collar shell, and the inner fixed disk is fixed on the core shaft; the first sliding surface 1311 and the second sliding surface 1312 are respectively the facing fitting surfaces of the inner fixed disk 192 of the rear sliding disk group and the outer fixed disk 191 of the rear sliding disk group; the third sliding surface 1321 and the fourth sliding surface 1322 are respectively the facing fitting surfaces of the outer fixed disk 182 and the inner fixed disk 181 of the front sliding disk group. Its unique advantage is that the drilling pressure transmission structure is arranged on the front and rear sides of the torque transmission structure.

[0042] When subjected to drilling pressure, the second sliding surface 1312 is closely fitted with the first sliding surface 1311, and the drilling pressure is directly transmitted from the mandrel 12 to the drill collar housing 11, and then to the mandrel 22 of the front adjacent transmission unit. When the high-reliability flexible drill pipe is lifted or removed, the drilling pressure transmission structure is subjected to tension, the third sliding surface 1321 is closely fitted with the fourth sliding surface 1322, and then the mandrel 12 drives the drill collar housing 11 backward.

[0043] At this time, the second sliding surface 1312 and the first sliding surface 1311 are convex spherical surfaces, the third sliding surface 1321 and the fourth sliding surface 1322 are convex spherical surfaces, and the centers of the spherical surfaces coincide with each other and coincide with the center of the universal joint of the torque transmission structure 14 .

[0044] Example 2

[0045] Different from the above embodiment, this embodiment specifically provides another specific structure of the drilling pressure transmission structure 13:

[0046] like Figure 2-3As shown in the figure, it is a preferred arrangement mode of the drilling pressure transmission structure 13 of the present invention, the direction indicated by the arrow in the figure is the front, the first sliding surface 1311 of the first sliding surface group 131 is arranged on the rear surface of the first sliding disk 15, the second sliding surface 1312 of the first sliding surface group 131 is arranged on the front surface of the spherical sliding disk 17, the third sliding surface 1321 of the second sliding surface group 132 is arranged on the rear surface of the spherical sliding disk 17, and the fourth sliding surface 1322 of the second sliding surface group 132 is arranged on the front surface of the second sliding disk 16. That is, the first sliding disk 15, the spherical sliding disk 17 and the second sliding disk 16 are sequentially arranged from front to back, the first sliding disk 15 and the second sliding disk 16 are fixed to the drill collar housing 11, and the spherical sliding disk 17 is fixed to the mandrel 12, and vice versa. When subjected to drilling pressure from the rear of the transmission unit, the second sliding surface 1312 fits tightly with the first sliding surface 1311, and transmits the drilling pressure from the mandrel 12 directly to the drill collar housing 11, and then to the mandrel 22 of the front adjacent transmission unit. When the high-reliability flexible drill pipe is lifted or removed, due to the influence of gravity or other factors, the third sliding surface 1321 fits tightly with the fourth sliding surface 1322, and then the mandrel 12 drives the drill collar housing 11 backward.

[0047] Preferably, the spherical sliding disk 17 is a convex disc structure to increase the stability of drilling pressure transmission. The corresponding first sliding surface 1311, second sliding surface 1312, third sliding surface 1321 and fourth sliding surface 1322 are all convex spherical structures, and their sphere centers always coincide. The sphere center is preferably located behind the second sliding disk.

[0048] At this time, the torque transmission structure should be arranged behind the drilling pressure transmission structure so that its center coincides with the center of the drilling pressure transmission structure.

[0049] The torque transmission structure 14 is a universal joint capable of transmitting torque, preferably a constant velocity universal joint, the input end of the universal joint is fixed to the mandrel 12 or the mandrel 12 is the input end of the constant velocity universal joint; the output end of the constant velocity universal joint is fixed to the drill collar shell 11 or the drill collar shell 11 is the output end of the constant velocity universal joint. That is, the universal joint can be arranged separately, or the outer surface of the mandrel 12 and the inner surface of the drill collar shell 11 can be integrally matched with the required universal joint structure to optimize the design, so as to shorten the axial length of the transmission unit as much as possible.

[0050] The universal joint may be a ball groove type torque transmission structure and / or a key groove type torque transmission structure and / or a gear tooth groove type torque transmission structure. As long as the torque can be directly transmitted from the mandrel 12 to the drill collar shell 11 within the maximum deflection angle (such as 8° or 5°) that can be generated between the axis of the mandrel 12 and the axis of the drill collar shell 11, the torque can be directly transmitted from the mandrel 12 to the drill collar shell 11, and vice versa (i.e., the torque is transmitted from the drill collar shell 11 to the mandrel 12).

[0051] Preferably, the universal joint is a ball-groove type torque transmission structure, the working principle of the ball-groove type torque transmission structure is the same as that of a ball-cage type constant velocity universal joint, or the ball-groove type torque transmission structure is the same as the ball-cage type constant velocity universal joint.

[0052] The ball-and-groove torque transmission structure includes a plurality of pairs (such as 3 or 4 pairs) of mutually cooperating twist balls 141 and ball grooves 142. The twist ball 141 moves in the ball groove 142, and the length of the ball groove 142 is greater than the diameter of the twist ball, so that the twist ball can generate spatial shaking in the ball groove, and when the axis of the mandrel and the drill collar shell deflects, within the deflection limit range, the twist ball will not get stuck at the edge of the ball groove. And the distance that the twist ball 141 can move forward and backward in the ball groove 142 is greater than the lubrication clearance of the spherical sliding disk 17 sliding between the first sliding disk 15 and the second sliding disk 16, and the distance from the center of each twist ball 141 to the center of the universal joint is equal and less than the distance from the first sliding surface group 131 and the second sliding surface group 132 to the center of the universal joint. Therefore, when drilling pressure and / or axial tension is generated, the torque transmission ball 141 does not bear the drilling pressure and / or axial tension.

[0053] Preferably, Figure 1 The ball groove 142 is opened on the core shaft 12 and the ball seat 111 fixed to the drill collar shell 11, so that the drill collar shell 11 is the input end of the universal joint, and the core shaft 12 is the output end of the universal joint, and vice versa. The torque transmission ball 141 is isolated from the external annulus by the elastic seal 6 and the dynamic sealing surface 7, so that other drilling impurities will not enter the ball groove 142 and affect the accuracy of torque transmission. At the same time, it can also provide a restoring force to keep the core shaft 12 and the drill collar shell 11 coaxial to a certain extent.

[0054] Preferably, the lubrication gap between the sliding surfaces of the first sliding surface group 131 and / or the second sliding surface group 132 is less than 1 mm, so as to further improve the stability of torque and rotational pressure transmission.

[0055] Preferably, the maximum deflection angle that the axis of the mandrel 12 can produce relative to the axis of the drill collar housing 11 does not exceed 8°, that is, the limit deflection angle of the input and output ends of the constant velocity universal joint does not exceed 8°. This is to protect the torque transmission structure 14 and the drilling pressure transmission structure 13 from increasing the overall length of a transmission unit due to excessive deflection angles, so as to improve the inclination rate of short radius or ultra-short radius wells. The high-reliability flexible drill pipe described in this embodiment can be connected in series with multiple transmission units, which can easily transmit drilling pressure and torque in a wellbore with a curvature of 5°-50° / m.

[0056] Preferably, the distance that the twist ball 141 can move forward and backward in the ball groove 142 is greater than the lubrication clearance between the sliding surfaces of the front sliding disc group 18 and the rear sliding disc group 19, and the distance from the center of each twist ball 141 to the center of the universal joint is equal and less than the distance from the first sliding surface group 131 and the second sliding surface group 132 to the center of the universal joint. When drilling pressure and / or axial tension are generated, the twist ball 141 does not bear drilling pressure and / or axial tension.

[0057] Preferably, a through structure 121 of equal diameter is provided inside the core shaft 12 of the transmission unit 1, and an electrical circuit 3 is provided inside the through structure 121;

[0058] There is an axial gap 4 between the core shaft 12 and the core shaft 22 of the adjacent transmission unit to facilitate the axial deflection of the core shaft 12 relative to the drill collar shell 11; and at least in the position where the axial gap 4 exists, the core shaft 12 is connected to the core shaft 22 of the adjacent transmission unit through an axial flexible jumper tube 5, and the axial flexible jumper tube 5 is arranged inside the through structure to prevent leakage of the drilling circulating medium (drilling fluid) and provide a linear axial restoring force after the core shaft 12 is axially deflected relative to the drill collar shell 11.

[0059] Preferably, the axial flexible jumper tube 5 is an elastic pressure-bearing tube, which can pass through the main channel and connect all the transmission units in series.

[0060] Example 3

[0061] A high reliability flexible drilling tool, such as Figure 4 As shown, the constant velocity universal joint includes a toothed torque transmission universal joint. The toothed torque transmission universal joint includes a torque transmission tooth groove 1431 at the mandrel end and a torque transmission tooth groove 1432 at the shell end, which are centrally symmetrically arranged. The mandrel end torque transmission tooth groove 1431 is fixedly connected to the mandrel, and the shell end torque transmission tooth groove 1432 is fixedly connected to the drill collar shell, so that torque can be transmitted between the drill collar shell and the mandrel through the toothed torque transmission universal joint. The tooth groove includes teeth, keyways, and tooth grooves.

[0062] Example 4

[0063] A high reliability flexible drilling tool and drilling system, such as Figure 5 As shown, including the above-mentioned high-reliability flexible drill pipe, the interior of the transmission unit is lubricated by lubricating liquid. Such as lubrication between the first sliding surface groups, between the second sliding groups, and between the torque transmission ball and the ball groove. The lubricating liquid in the lubricating liquid system mainly refers to lubricating oil and / or grease. A plurality of transmission units constitute a high-reliability flexible drill pipe, and each of the high-reliability flexible drill pipes is electrically connected through a conductive slip ring 9. Since the high-reliability flexible drill pipe can transmit drilling pressure and torque separately through the drilling pressure transmission structure 13 and the torque transmission structure 14, the drilling pressure and torque can be transmitted separately during the drilling process of the drilling tool, which reduces the strength requirements of the drilling tool, increases the service life, greatly reduces the drilling cost, and can achieve stable inclination, with an inclination rate of up to 15°-50° per 10 meters.

[0064] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A high reliability flexible drill pipe, characterized in that: The invention comprises a plurality of transmission units connected end to end, wherein the transmission unit comprises a drill collar shell, a mandrel, a drilling pressure transmission structure and a torque transmission structure, wherein one end of the drilling pressure transmission structure is fixed to the drill collar shell and the other end is fixed to the mandrel; the drilling pressure and axial tension between the drill collar shell and the mandrel are directly transmitted through the drilling pressure transmission structure; One end of the torque transmission structure is fixed to the drill collar shell, and the other end is fixed to the mandrel; the torque between the drill collar shell and the mandrel is transmitted through the torque transmission structure; the drilling pressure transmission structure is independently arranged from the torque transmission structure, and the deflection center of the drilling pressure transmission structure and the deflection center of the torque transmission structure coincide with each other; one end of the mandrel is fixedly connected to the drill collar shell of the adjacent transmission unit or the mandrel and the drill collar shell of the adjacent transmission unit are designed as an integrated structure to realize the transmission of drilling pressure and torque between adjacent transmission units, The drilling pressure transmission structure at least includes a first sliding surface group for bearing axial pressure, the first sliding surface group includes a first sliding surface fixed to the drill collar shell and a second sliding surface fixed to the mandrel, the first sliding surface and the second sliding surface are in contact with each other and can slide relatively around the deflection center, so that when the axes of the drill collar shell and the mandrel are deflected, the direction of axial pressure transmission can be deflected without loss or with low loss; The drilling pressure transmission structure also includes a second sliding surface group for bearing axial tension, the second sliding surface group includes a third sliding surface fixed to the mandrel and a fourth sliding surface fixed to the drill collar shell, the third sliding surface and the fourth sliding surface are in contact with each other and can slide relatively around the deflection center, so that when the axis of the drill collar shell and the mandrel deflects, the direction of axial tension transmission can be deflected without loss or with low loss. The transmission unit at least includes a front sliding disc group and a rear sliding disc group, the front sliding disc group is arranged at the front end of the torque transmission structure, and the rear sliding disc group is arranged at the rear end of the torque transmission structure; the front sliding disc group and the rear sliding disc group both include an outer fixed disc and an inner fixed disc, the outer fixed disc is fixed on the drill collar shell, and the inner fixed disc is fixed on the core shaft; the first sliding surface and the second sliding surface are respectively the facing fitting surfaces of the inner fixed disc and the outer fixed disc of the rear sliding disc group; the third sliding surface and the fourth sliding surface are respectively the relative fitting surfaces of the outer fixed disc and the inner fixed disc of the front sliding disc group, and the distance from the torque transmission structure to the deflection center is smaller than the distance from the drilling pressure transmission structure to the deflection center.

2. The high reliability flexible drill pipe according to claim 1, characterized in that: The transmission unit includes a first sliding disk, a second sliding disk and a spherical sliding disk, the spherical sliding disk is fixed on the core shaft, the second sliding surface and the third sliding surface are the front surface and the rear surface of the spherical sliding disk respectively; the first sliding disk is fixed to the drill collar shell and the first sliding surface is arranged on the rear surface of the first sliding disk, the second sliding disk is fixed to the drill collar shell and the fourth sliding surface is arranged on the front surface of the second sliding disk, and the first sliding disk, the second sliding disk and the spherical sliding disk all slide around the deflection center of the drill collar shell and the core shaft.

3. The high reliability flexible drill pipe according to any one of claims 1-2, characterized in that: The torque transmission structure includes a constant velocity universal joint, the input end of the constant velocity universal joint is fixed to the core shaft or the core shaft is the input end of the constant velocity universal joint; the output end of the constant velocity universal joint is fixed to the drill collar shell or the drill collar shell is the output end of the constant velocity universal joint.

4. The high reliability flexible drill pipe according to claim 3, characterized in that: The torque transmission structure is a ball-cage type constant velocity universal joint, including multiple pairs of ball grooves and torque-transmitting balls moving in the ball grooves. The length of the ball grooves is greater than the diameter of the torque-transmitting balls, so that the torque-transmitting balls can produce spatial shaking in the ball grooves, and when the axis of the core shaft and the drill collar housing deflects, within the deflection limit range, the torque-transmitting balls will not get stuck at the edge of the ball grooves.

5. The high reliability flexible drill pipe according to claim 4, characterized in that: The distance from the center of each of the torque transmission balls to the center of the constant velocity universal joint is equal and smaller than the distance from the first sliding surface group and the second sliding surface group to the center of the constant velocity universal joint.

6. The high reliability flexible drill pipe according to claim 1, characterized in that: The torque transmission structure is a tooth-groove type torque transmission structure; the tooth-groove type torque transmission structure includes at least a first tooth groove and a second tooth groove, the first tooth groove is fixed to the core shaft, and the second tooth groove is fixed to the drill collar shell, so that torque can be transmitted between the drill collar shell and the core shaft through the tooth groove.

7. The high reliability flexible drill pipe according to claim 1, characterized in that: A gap between the sliding surfaces of the first sliding surface group and / or the second sliding surface group is less than 1 mm.

8. The high reliability flexible drill pipe according to claim 1, characterized in that: The maximum deflection angle that can be generated by the axis of the mandrel relative to the axis of the drill collar housing does not exceed 8°.

9. The high-reliability flexible drill pipe according to claim 1, characterized in that: A through structure of equal diameter is provided inside the core shaft, and an axial gap exists between the core shaft and the core shaft of an adjacent transmission unit to facilitate axial deflection of the core shaft relative to the drill collar shell; and at least at the position where the axial gap exists, the core shaft is connected to the core shaft of the adjacent transmission unit through an axial flexible jumper tube, and the axial flexible jumper tube is arranged in the through structure.

10. A high reliability flexible drilling system, characterized in that: It comprises the high-reliability flexible drill pipe as described in claim 8 or 9, and also comprises an elastic seal and / or a dynamic sealing surface, a sealing space is formed between the elastic seal and / or the dynamic sealing surface and the axial flexible jumper tube, and the sealing space is filled with lubricating fluid for lubricating the transmission unit.

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