Threaded connection joint for oil pipe of oil gas well and sealing method

Abstract

The invention relates to the technical field of oil pipe pressure connection, and particularly discloses a threaded connection joint for an oil pipe of an oil gas well, which comprises a coupling and a pipe body, the coupling is provided with an internal thread, the end part of the pipe body is provided with an external thread, the coupling and the pipe body are in threaded connection through the internal thread and the external thread, and the internal thread and the external thread are consistent in thread shape. The angle range of the thread angle alpha of the thread is 45-50 degrees, the angle value of the thread angle alpha is equal to the thread flank angle alpha 1 of the bearing face of the thread and the thread flank angle alpha 2 of the guiding face of the thread, the angle range of the thread flank angle alpha 1 is 0-5 degrees, and the guiding face and the bearing face of the thread are connected through the oval face of the thread top or the oval face of the thread bottom. The connection strength of the threaded connection joint is equal to or superior to that of an EU threaded joint, the threaded connection joint can replace the EU threaded joint to be used on an oil pipe of an oil gas well, and the problem that the EU threaded joint is high in repairing and recycling cost is solved.

Description

Technical Field

[0001] The invention relates to the technical field of oil pipe pressure connection, in particular to a threaded connection joint for oil pipes in oil and gas wells and a sealing method. Background Art

[0002] At present, the API connection threads commonly used in oil and gas well tubing include non-thickened tubing threads (code NU) and external thickened tubing threads (code EU). When processing NU, the steel pipe end does not need to be upset and thickened, but the connection strength of NU is only 60% of the steel pipe body, resulting in insufficient performance of NU and surplus performance of the pipe body. In order to make the connection strength of NU thread equal to that of the steel pipe body, the existing standard performs additional upset and thickening on the steel pipe end without changing the thread shape, and the size of the thread is also enlarged to make its connection strength equal to that of the steel pipe body. This is the external thickened tubing thread EU joint in the standard, and the tubing with this thread EU joint is referred to as EU tubing. EU oil pipes solve the problem of equal strength, but oil pipes can be reused. When used repeatedly, thread damage is inevitable. When the threads are damaged and need to be cut and reprocessed, the thickened part of the pipe end is cut off and EU thread processing cannot be performed. It takes many steps to perform upsetting processing on the over-cut oil pipe, and the cost is much greater than purchasing a new oil pipe. This is the reason why EU oil pipes cannot be repaired and reused.

[0003] The patent of this invention designs a special threaded joint, which does not require upsetting and thickening of the steel pipe end during processing. The connection strength of the threaded joint can reach the same level as the pipe body, and the sealing performance is equivalent to that of the EU oil pipe. The patent of this invention solves the problem that the EU oil pipe thread cannot be repaired. Its connection strength, sealing performance, anti-galling performance, and convenient buckling operation are equivalent to or stronger than those of the EU oil pipe joint, and can replace the API EU threaded joint for use on oil and gas well pipes.

[0004] The patent document (China Patent Publication No.: CN212454292U) discloses a tubing joint. The invention relates to a steel pipe joint end face sealing device and sealing method, the device is composed of a sealing and anti-torque shoulder, a serrated thread profile, etc. The invention can replace the EU tubing joint. However, the invention has an end face shoulder, which plays a sealing role, and there is a large gap between the internal and external thread crests and tooth sides, and there is no sealing between the threads.

[0005] The patent document (China Patent Publication No.: CN201574697U) discloses a stepped-buckle oil casing gas-tight threaded connection structure. The utility model provides a stepped-buckle oil casing gas-tight threaded connection structure, which includes a pipe body with an external thread at one end and a coupling with an internal thread that are screwed together. The external thread of the pipe body and the internal thread of the coupling are both stepped-cone threads, and the length of the internal thread of the coupling is such that the two ends with the external thread are screwed into the end faces of the pipe body to reach the top. The effect of the utility model is that the design of the stepped-buckle end faces facing the top blocks the channel for oil and gas leakage, but there are leakage channels on the top and side of the threads connected to the threads, and does not involve a single thread-to-thread sealing problem.

[0006] The patent document (China Patent Publication No.: CN202039789U) discloses a tubing joint that is interchangeable with an API joint. The patent involves a tubing joint connection structure, where the joint outer diameter, field end thread size, etc. are completely consistent with the API thread, but the external thread nose is extended by the length of the J value (generally 12.7mm), so that after the joint is tightened, the end faces of the two pipes are pressed against each other, generating contact pressure for sealing. However, the patent is a multi-top seal of the end face of the pipe, and does not involve the single thread-thread sealing problem and the equal pipe body strength problem of the threaded connection.

[0007] The patent document (China Patent Publication No.: CN202611614U) discloses a thread structure of a gas-tight threaded joint for low-pressure gas fields. The patent involves a thread-to-thread sealing structure. However, the thread used in the patent is similar to the API round thread tooth type and does not involve the problem of equal pipe body strength of the threaded connection. Summary of the invention

[0008] The purpose of the present invention is to provide a threaded connection joint for oil and gas well tubing, which has a connection strength equal to or better than that of an EU threaded joint and can replace an EU threaded joint for use on oil and gas well tubing, thereby solving the problem of high cost of repairing and reusing an EU threaded joint.

[0009] The purpose of the present invention can be achieved through the following technical solutions:

[0010] A threaded connection joint for oil and gas well tubing, comprising a coupling and a pipe body, wherein the coupling is provided with an internal thread, and an end of the pipe body is provided with an external thread, wherein the coupling and the pipe body are threadedly connected via the internal thread and the external thread, wherein the thread shapes of the internal thread and the external thread are consistent, wherein the angle range of the thread profile angle α is 45°-50°, wherein the angle value of the thread profile angle α is equal to the load-bearing surface flank angle α1 and the guide surface flank angle α2 of the thread, wherein the angle range of the flank angle α1 is 0-5°, and the guide surface and the load-bearing surface of the thread are connected via an elliptical surface of a tooth top or a tooth bottom.

[0011] In a further embodiment, when the coupling and the pipe body are connected by the thread, an interference fit is adopted at least at the elliptical surfaces of the crest and the bottom of the thread.

[0012] In a further embodiment, the pitch p of the thread is 3.175 mm and the taper T is 1 / 16.

[0013] In a further solution, the tube body includes a left end steel tube and a right end steel tube.

[0014] In a further embodiment, the thread is a right-hand thread.

[0015] In a further solution, a mechanical tightening mark and a hand tightening mark are provided on the tube body.

[0016] In a further embodiment, the thread profile height is equal to the API 10 thread profile height.

[0017] In a further solution, any of the above-mentioned threaded connection joints for oil and gas well tubing is used;

[0018] After the threads are screwed together, they are interference fit, and the gaps between the external thread crest cs and the internal thread root rn, between the external thread root rs and the internal thread crest cn, and between the internal and external thread flanks can be bridged by metal flow due to elastic deformation and plastic deformation.

[0019] In a further embodiment, the thread is lubricated by thread grease during the screwing process.

[0020] In a further solution, after the thread reaches the hand-tightening mark set on the pipe body through manual tightening during the screwing process, the pre-tightening torque is loaded through machine tightening to make the end face of the coupling reach the machine-tightening mark position set on the pipe body.

[0021] Beneficial effects of the present invention:

[0022] The thread crest of the present invention is an elliptical structure. When connected, the thread produces an interference fit to form metal plastic flow to fill the gap between the thread crest and the tooth side, forming a stable seal, achieving the sealing performance of API external thickened oil pipe (see GB / T9711-2022, code EU). The thread of the present invention also adopts a smaller load-bearing tooth side angle and a larger guide tooth side angle. The connection strength of the thread is equivalent to the strength of the pipe body, achieving the effect of equal pipe body strength. Without thickening the pipe end, the processed special thread fully meets the performance of API external thickened oil pipe of the same specification, and can replace API external thickened oil pipe thread, and the processing and construction operation are convenient, without adding additional costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 Schematic diagram of partial engagement of the connecting threads of a pipe joint in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the connection principle of one side of the inner side of the coupling in an embodiment of the present invention;

[0026] Figure 3 It is a schematic diagram of a coupling in which both ends of the coupling are connected to steel pipes in an embodiment of the present invention;

[0027] In the figure: 1. Coupling; 2. Left end steel pipe; 3. Right end steel pipe; 4. Thread; 5. Triangular mark of machine tightening position; 6. Machine tightening mark position; 7. Hand tightening mark position. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] like Figure 3 As shown, a threaded connection joint for oil and gas well oil pipes includes a coupling 1 and a pipe body, wherein the coupling 1 is provided with an internal thread, and the end of the pipe body is provided with an external thread, and the coupling 1 and the pipe body are screwed together through the internal thread and the external thread, and the thread shapes of the internal thread and the external thread are consistent, see Figure 1As shown, where: H represents the original triangle height of the thread profile; hs represents the actual height of the thread profile; h1 represents the effective height of the thread profile; α1 represents the load-bearing surface tooth side angle; α2 represents the guide surface tooth side angle; α represents the tooth profile angle; the angle range of the thread profile angle α is 45°-50°, and the tooth profile height is close to or equal to the API 10 tooth circle thread (i.e., there are 10 threads within an axial length of 25.4mm), and the angle value of the tooth profile angle α is equal to the load-bearing surface tooth side angle α1 and the guide surface tooth side angle α2 of the thread, and the angle range of the tooth side angle α1 is 0-5°. The load-bearing surface of the connecting thread adopts a tooth side angle α1 close to 0° for the best, and the guide surface of the connecting thread adopts a tooth side angle α2 close to 45° for the best. However, since interference fit is usually used during connection, it is screwed together within the range of 0-5°. Since it can be filled by metal flow, it can provide the same The guide surface and the bearing surface of the thread are connected through the elliptical surface of the tooth top or the tooth bottom, which reduces the height of the upper half of the original tooth type that contributes little to the strength of the thread connection, and increases the proportion of the effective height of the thread tooth type in the actual height of the thread. It can be used for oil pipes with small wall thickness. After the threads are screwed together, they have an interference fit. The gap between the external thread tooth top cs and the internal thread tooth bottom rn (or the external thread tooth bottom rs and the internal thread tooth top cn) and the gap between the internal and external thread tooth sides can be bridged by the metal flow of elastic deformation and plastic deformation to achieve good sealing.

[0030] According to the above working principle, some preferred implementation structures or embodiments are provided. When the coupling 1 and the pipe body are connected through the thread 4, an interference fit is adopted at least at the elliptical surfaces of the crest and the root.

[0031] The preferred thread pitch p is 3.175 mm, and the taper T is 1 / 16. Reference may also be made to existing special thread settings such as EU or NU.

[0032] The thread is right-hand thread, which is more in line with processing habits.

[0033] There are mechanical tight marks and hand tight marks on the tube body, which makes it easy to understand the degree of screwing.

[0034] Specifically, when the oil and gas well oil pipe is connected by the threaded connection joint, Figure 2 As shown, D represents the position when the pipe body and the coupling 1 begin to be screwed together. After the hand-tightening screwing distance L4, the hand-tightening position is reached, that is, the position of the hand-tightening mark distance A1. Then, the pre-tightening torque can be loaded by machine tightening, such as by hand tightening with a torque wrench, until the machine tightening position is reached. J represents the reserved extension length, which is generally 12.7mm.

[0035] After the threads are screwed together, they are interference fit, and the gaps between the external thread crest cs and the internal thread bottom rn, the external thread bottom rs and the internal thread crest cn, and the internal and external thread flanks can be bridged by metal flow due to elastic and plastic deformation.

[0036] The threads are lubricated with thread grease during the screwing process.

[0037] It should be understood by those skilled in the art that the above-mentioned threaded connection joint for oil and gas well oil pipes is mostly used to connect two sections of oil pipes when in use. Generally, the oil pipes are made of steel pipes, and the ends of the two sections of oil pipes are connected by a coupling 1. Figure 3 As shown, the left end steel pipe 2 and the right end steel pipe 3 are two sections of the oil pipe connected by the coupling 1, and are screwed together by the thread 4. During the screwing process, the thread 4 is manually tightened to the hand tightening mark set on the pipe body, as shown in FIG. Figure 3 After the hand-tightening mark position 7 is reached, the coupling 1 is tightened continuously by a torque pliers or torque wrench, and the pre-tightening force is applied to continue tightening, so that the end face of the coupling 1 reaches the bottom edge of the triangular mark 5 of the steel pipe 3, that is, Figure 3 At the tightening mark position 6 marked in the middle, the left end steel pipe 2 and the right end steel pipe 3 can be screwed together by this method.

[0038] According to the above principle, several pieces of No. 1 and No. 2 samples with the specification of Φ73.01×5.51mm N80 were processed. Ordinary thread grease was used, and the make-up torque was 2000Nm. The threads of No. 1 and No. 2 samples were not sticky. After the final make-up, the No. 1 sample was subjected to an air tightness test. The joint had no leakage when the air pressure was maintained at 36MPa for 30 minutes. After the pressure was released, a pull-off test was carried out, and the pipe body broke at 1311KN. The No. 2 sample was subjected to a water pressure and bursting test. The threaded joint had no leakage when the pressure was maintained at 79MPa for 30 seconds. The pipe body burst when the pressure was continued to be 110MPa. The test results fully achieved the connection performance of the AP I external thickened oil pipe Φ73.01×5.51mm N80. In addition, for other specifications of AP I external thickened EU oil pipes, the above-mentioned pipe joints of the same level specifications can also meet their connection performance requirements.

[0039] It should be noted that the terms "first", "second" etc. in the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged in appropriate circumstances, so that the embodiments of the present application described here. In the present application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal" etc. are based on the orientation or positional relationship shown in the accompanying drawings.

[0040] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0041] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A threaded connection joint for oil and gas well oil pipes, comprising a coupling (1) and a pipe body, wherein the coupling (1) is provided with an internal thread, and an end of the pipe body is provided with an external thread, wherein the coupling (1) and the pipe body are screwed together through the internal thread and the external thread, and the threads (4) of the internal thread and the external thread have the same shape, and wherein: The angle range of the tooth profile angle (α) of the thread (4) is 45°-50°, the angle value of the tooth profile angle (α) is equal to the load-bearing surface flank angle (α1) and the guide surface flank angle (α2) of the thread, the angle range of the flank angle (α1) is 0-5°, and the guide surface and the load-bearing surface of the thread are connected by an elliptical surface of the tooth top or tooth bottom.

2. A threaded connection joint for oil and gas well tubing according to claim 1, characterized in that: When the coupling (1) and the pipe body are connected via the thread (4), interference fit is adopted at least at two of the elliptical surfaces at the top and the bottom of the thread.

3. The threaded connection joint for oil and gas well tubing according to claim 1, characterized in that: The pitch (p) of the thread (4) is 3.175 mm, and the taper T is 1 / 16.

4. The threaded connection joint for oil and gas well tubing according to claim 1, characterized in that: The tube body comprises a left end steel tube (2) and a right end steel tube (3).

5. The threaded connection joint for oil and gas well tubing according to claim 1, characterized in that: The thread (4) is a right-hand thread.

6. The threaded connection joint for oil and gas well tubing according to claim 1, characterized in that: The tube body is provided with a mechanical tightening mark and a hand tightening mark.

7. The threaded connection joint for oil and gas well tubing according to claim 1, characterized in that: The thread profile height of the thread (4) is equal to the API10 thread profile.

8. A sealing method for a threaded connection joint for oil and gas well oil pipes, characterized in that: A threaded connection joint for oil and gas well tubing according to any one of claims 1 to 7; The threads (4) are interference fit after being screwed together, and the gaps between the external thread crest (cs) and the internal thread root (rn), between the external thread root (rs) and the internal thread crest (cn), and between the internal and external thread flanks can be bridged by metal flow due to elastic deformation and plastic deformation.

9. A sealing method for a threaded connection joint for oil and gas well tubing according to claim 8, characterized in that: The thread (4) is lubricated by thread grease during the screwing process.

10. A sealing method for a threaded connection joint for oil and gas well tubing according to claim 8 or 9, characterized in that: During the screwing process, the thread (4) is manually tightened to reach the hand-tightening mark provided on the pipe body, and then mechanically tightened to achieve loading of the pre-tightening torque, so that the end face of the coupling (1) reaches the position of the mechanical tightening mark provided on the pipe body.

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