EA026614B1 - Sealed threaded joint for casing pipes - Google Patents

Abstract

The invention is related to the oil and gas extraction industry. A joint comprises male and female elements with trapezoidal buttress threads at their ends, the threads having 1:16 taper, a slope angle between the thread profile lead-in flank and the thread axis normal line of 10-30°, and a slope angle of the bearing flank of 0 to -10°. The outer sealing unit is formed by radial sealing surfaces extending at an angle of 7-12° to the thread axial line, and bearing end surfaces made at an angle of 5-17° to the thread axis normal line. The inner sealing unit is formed by radial sealing surfaces extending at an angle of 1.5-4.0° to the thread axial line. In a length equal to 20-40% of the total thread length on the male end, beginning from the first thread, machining of the threads is performed for decreasing their height to 50% of the total thread profile height. On the female element, in the thread run-out area, a circumferential groove is made, the transition from the groove surface to the radial sealing surface being spherical. Provided are gas tightness of the joint under action of multidirectional loads, better screwing properties and higher wear resistance of the joint.

Description

The claimed invention relates to threaded joints of casing pipes and can be used to connect elements of casing pipes used in the construction, operation and repair of oil, gas and gas condensate wells, including those with a high intensity of curvature.

Casing pipes for oil, gas and gas condensate wells are operated in difficult conditions - in the presence of aggressive working environments and with significant multidirectional combined mechanical loads. In this regard, the main requirement for threaded joints of casing pipes is to maintain the tightness of the connection, including gas, at high levels of mechanical stress. To ensure long-term, trouble-free operation of casing pipes, threaded joints must have high wear resistance with repeated make-up and unscrewing of the joint.

The prior art knows a tight threaded connection of casing pipes containing male and female elements, at the ends of which on the outer and inner surfaces, respectively, are made of trapezoidal tapered threads. At the same time, the connection is made with external and internal sealing units. The external sealing connection unit is formed by contacting thrust end surfaces made on male and female elements. The internal sealing connection node is formed by radial sealing surfaces contacting each other, made on male and female elements. A circumferential groove of a triangular profile (KI 2256767 C1, 07.20,2005 (1) is made on the female element at the thread exit.

The tight threaded casing joint disclosed in document (1) does not provide the level of tightness required during operation of the casing joint, including in gas and gas condensate wells, due to insufficient contact stresses provided by the sealing surfaces of the sealing units.

This technical solution (1) was adopted as a prototype of the claimed invention.

The task to which the claimed invention is directed is the creation of a threaded connection of casing pipes with high tightness, including gas, under the action of multidirectional mechanical loads (tensile, compressive, bending, torque) in various combinations thereof.

The technical result provided by the claimed invention is to preserve the gas tightness of the joint under the influence of significant multidirectional combined mechanical loads, improve the make-up characteristics of the joint, increase its wear resistance, and ensure equal passage of the casing string along the inner diameter.

The hermetic threaded connection of the casing pipes includes male and female elements, at the ends of which on the outer and inner surfaces, respectively, made resistant trapezoidal tapered threads with a taper of 1:16. The angle of inclination of the embedded edge of the thread profile of the thread on the male and female elements is 10-30 ° to the normal of the axial line of the thread, and the angle of inclination of the reference face of the profile of the thread spiral is from 0 to -10 ° to the normal of the axial thread line.

A circumferential groove is made on the female element at the thread exit.

At the same time, the connection is made with external and internal sealing units.

The external sealing assembly is formed by radial sealing surfaces contacting each other and thrust end surfaces made on the male and female elements. Moreover, the persistent end surfaces of the male and female elements are made at an angle of 5-17 ° to the normal to the axial line of the thread, provided that the angle of inclination of the persistent end surface of the male element exceeds the angle of inclination of the persistent end surface of the female element. The radial sealing surfaces of the male and female elements are made at an angle of 7-12 ° to the center line of the thread.

The internal sealing assembly is formed by radial sealing surfaces contacting each other, made on male and female elements. Moreover, the radial sealing surfaces of the male and female elements are made at an angle of 1.5-4.0 ° to the axial line of the thread, provided that the angle of inclination of the sealing surface of the male element exceeds the angle of inclination of the sealing surface of the female element. In addition, on the female member, the transition from the radial sealing surface to the surface of the circumferential groove is made spherical.

At a length equal to 20-40% of the total length of the thread made on the male element, starting from the thread approach, the specified thread was pumped with a decrease in its height to 50% of the total thread profile height of the male element.

In the particular case of the invention, the circumferential groove at the thread exit of the female element has a triangular profile.

In the particular case of the invention, the radius of the sphere along which the transition from the radial sealing surface of the enclosing element to the surface of the circumferential groove is made is 1-3 mm.

In FIG. 1 shows the claimed hermetic threaded connection of the casing assembly.

In FIG. 2 shows an external sealing joint assembly.

In FIG. 3 shows a thrust trapezoidal conical thread of a joint.

In FIG. 4 shows an internal sealing joint assembly.

The hermetic threaded connection of the casing pipes comprises male (1) and female (2) elements, on the ends of which on the external and internal surfaces, respectively, made resistant trapezoidal conical threads (3).

The male element (1) is the nipple portion of the pipe. The covering element (2) is the bell-shaped part of the pipe.

The thread twist profile (3) is an isosceles trapezoid whose sides are made in the form of a support (4) and embedded (5) faces having different angles of inclination to the normal to the axis of the thread line. When making a connection with such a thread, the support faces (4) of the thread twist profile (3) on the male and female elements are in contact with each other and perceive axial tensile loads acting on the connection, which ensures high joint strength. At the same time, when screwing the joint along the embedded edges (5) of the thread twist profile, a constructive gap is formed, which improves the screwing characteristics of the joint - the possibility of multiple screwing-unscrewing without damage (scoring) of the contacting surfaces of the thread and while maintaining the operational characteristics of the joint, preventing the joint from jamming during assembly .

Threads (3) on male (1) and female (2) elements are made with a taper of 1:16. The execution of threads with a taper of 1:16 on the one hand provides a high degree of engagement with each other when making the connection and the possibility of the perception by the connection of bending and tensile loads acting during operation of the connection, on the other hand, it maintains high screwing characteristics of the connection.

The angle of inclination of the embedded face (5) of the thread thread profile (3) on the male (1) and female (2) elements is 10-30 ° to the normal of the axial thread line, and the angle of inclination of the support face (4) of the thread thread profile (3) is from 0 to -10 ° to the normal to the center line of the thread.

By the normal of the axial line of the thread is meant the perpendicular drawn to the axial line of the thread (Fig. 3).

A negative angle (from 0 to -10 °) of the inclination of the support face (4) of the thread twist profile (3) excludes the possibility of thread (3) coming out of male (1) and female (2) elements from each other under significant tensile loads, acting on the connection under the action of the dead weight of the column lowered into the well. A reduction in the radial interference in the thread is also achieved, which ensures high wear resistance of the joint, improves its performance under increased loads.

Performing the inclination angle of the embedded face (5) of the thread thread profile (3) of 10-30 ° to the normal of the center line of the thread (3) facilitates the screwing of the connection by stabilizing the position of the male (1) and female (2) elements relative to each other at the initial stage make-up, which prevents jamming of the joint and damage (seizure) of the surfaces of the threads (3). The above implementation of the embedded face (5) of the thread twist profile (3) also increases the wear resistance of the joint when it is repeatedly screwed-unscrewed while maintaining a high degree of tightness.

The connection is made with internal (6) and external (7) sealing units. The presence in the connection of two sealing units (6), (7), radial sealing (8), (9), (10), (11) and persistent end (12), (13) surfaces of which are in contact with significant contact stresses , with the occurrence of deformation in the elastic region and the formation of a metal-metal seal, it provides high tightness of the joint when it is exposed to multidirectional combined mechanical loads.

The external sealing assembly (7) of the connection is formed by radial sealing (8), (9) in contact with each other and persistent end (12), (13) surfaces made on the male and female elements. Moreover, the persistent end surfaces (12), (13) of the male (1) and female (2) elements are made at an angle of 5-17 ° to the normal to the axial line of the thread, provided that the angle of inclination of the resistant end surface (13) of the male (1) ) of the element above the angle of inclination of the persistent end surface (12) of the covering (2) element. The radial sealing surfaces (8), (9) of the male (1) and male (2) elements are made at an angle of 7-12 ° to the axial line of the thread.

The execution of the persistent end surfaces (12), (13) of the external sealing assembly (7) at an angle of inclination of 5-17 ° to the normal to the axial line of the thread, provided that the angle of inclination of the persistent end surface of the male element exceeds the angle of inclination of the persistent end surface of the female element, provides preloading and fixing of the radial sealing surfaces (8), (9) of the external sealing unit (7). In addition, precise positioning of the driven (1) and covering (2) elements relative to each other, accurate fixation of a predetermined interference and torque value during make-up of the joint — that is, improved make-up characteristics, and the ability to control the make-up of the joint — are ensured. Also, the large contact area of the persistent end surfaces (12), (13) with each other when making the connection allows you to increase the make-up torque while maintaining contact stresses at the required level within the elastic deformation.

With an increase in the indicated inclination angles of the persistent end surfaces (12), (13) above the stated limits, significant deformations of the inner diameter of the enclosing element (2) begin to arise upon compression or twisting of the joint. If the angles decrease below the stated limits, the wedge effect is lost, since the wedge of the enclosing element (2) becomes more rigid in the axial direction.

The location of the radial sealing surfaces (8), (9) of the covered (1) and covering (2) elements of the external sealing assembly (7) at an angle of 7-12 ° to the axial line of the thread provides an optimal contact area and a high level of stresses of the surfaces contacting each other male and female elements, ensuring the tightness of the connection with all combinations of loads acting on it.

The internal sealing unit (6) is formed by radial sealing surfaces (10), (11) in contact, which are made on male (1) and female (2) elements. Radial sealing surfaces (10), (11) are made at an angle of 1.5-4.0 ° to the axial line of the thread, provided that the angle of inclination of the sealing surface (11) of the male element (1) exceeds the angle of inclination of the sealing surface (10) of the female element (2).

The end surfaces (14), (15) of the internal sealing unit (6), made on the male and female elements, are located at an angle of 89.5-90.5 ° to the center line of the thread.

Internal equidistance (isolation of the inner contour of the casing string as a whole), provides unhindered passage of downhole equipment inside the casing, which increases the operational efficiency of the connection.

The location of the radial sealing surfaces (10), (11) of the male (1) and female (2) elements of the internal sealing assembly (6) at an angle of 1.5-4.0 ° to the axial line of the thread, provided that the angle of inclination of the sealing surface ( 11) the male element (1) above the angle of inclination of the sealing surface (10) of the female element (2), provides an optimal contact area and a high level of stresses of the contact surfaces of the male (1) and female (2) elements, ensuring a tight connection When all combinations of limit loads.

A circumferential groove (17) is made on the enclosing element (2) at the thread exit, designed to divert the thread-cutting tool without damaging the connection surfaces, and also to place excess thread sealing grease in the cavity formed by it when screwing the joint. In addition, when cutting a thread on a female element (2), at the place where the thread comes off at the edges of the thread tops (3), burrs appear protruding toward the center line of the thread (3). The presence of these burrs leads to damage to the radial sealing surface (11) of the male element (1) during make-up of the joint, to the formation of scoring on it, which subsequently affects the tightness and wear resistance of the joint. The circumferential groove (17), made at the thread exit (3) of the female element (2), eliminates the burrs on the edges of the threads from the contact area with the radial sealing surface (11) of the male element (1).

The transition (18) from the radial sealing surface (10) to the surface of the circumferential groove (17) located on the thread exit of the female element (2), spherical provides an increase in the contact area of the radial sealing surfaces (10), (11) of the covered (1) and covering (2) elements and a high level of stresses of the indicated surfaces (10), (11), ensuring the tightness of the connection for all combinations of ultimate loads.

The radius of the sphere along which the transition (18) is made from the radial sealing surface (10) of the enclosing element (2) to the surface of the circumferential groove (17) is 1-3 mm.

At a length (16) equal to 20-40% of the total length of the thread (3) made on the male element (1), starting from the thread approach, the specified thread was pumped with its height reduced to 50% of the total thread profile height (3 ) of the covered element (1). The thread (3) is threaded on the male element (1) by cutting the thread (3) over a length of 20-40% of the total length of the thread (3) and in height up to 50% of the total height of the thread profile (3).

The implementation of the above threading of the thread (3) on the female element (1) increases the approach (establishment) of the male element (1) in the female element (2) during assembly of the connection, which provides improved alignment and easy make-up of the connection at the initial stage, which can be decisive value when assembling the connection in the field in the absence of special instruments for alignment.

Pulling the thread (3) on the female element (1) to a length of less than 20% of the total length of the thread (3) will not lead to the above-described effect of improving alignment. Excess

- 3,026,614 the length of threading of the thread (3) on the female element (1) above 40% of the total length of the thread (3) will lead to a noticeable decrease in the perception of axial tensile loads by the thread and increase the likelihood of threads (3) coming out of engagement with each other.

Exceeding the thread penetration height (3) on the female element (1) by more than 50% of the total thread profile height (3) will also lead to a noticeable decrease in the perception of axial tensile loads by the thread and increase the likelihood of the threads (3) coming out of engagement with each other.

Sealed threaded connection of casing works as follows.

When performing the screwing operation of the joint, the male (1) and female (2) elements are initially interacted with the help of persistent trapezoidal tapered threads (3) made at the ends on the outer surface of the male element (1) and the inner surface of the female element (2).

In the process of making up the connection, the radial sealing surface (11) of the male element (1) advances along the circumferential groove (17) made on the female element (2), then the sealing surface (11) of the male element (1) of the internal sealing unit (6) interacts with a sealing surface (10) of the female member (2). Due to the diametrical deformations of the conical sealing surfaces (10), (11), a metal-metal seal is created.

At the same time, the radial sealing surfaces (8), (9) and the thrust end surfaces (12), (13) of the external sealing assembly (7) interact.

The end of the process of screwing the connection occurs when the thrust end surfaces (12), (13) are closed, made on the male (1) and female (2) elements of the external sealing assembly (7).

An example embodiment of the invention.

To test the claimed tight threaded connection of the casing pipes, samples (No. 1, 2) were made - casing pipes with a diameter of 139.7 mm, a wall thickness of 6.98 mm, and a length of 11 m with upset ends. On the external surface of the male element (1) and the internal surface of the female element (2), resistant trapezoidal threads (3) were applied with a taper of 1:16, a pitch of 4.233 mm, a thread thread height of 1.2 mm, and external elements (7) were formed and internal (6) sealing units.

In addition, samples were made (No. 3, 4) of the prototype.

The main characteristics of the samples are given in table 1.

Tests of the samples were carried out on the multiple make-up and unscrewing and gas tightness of the compound.

Table 1

sample No. 1 sample Number 2 sample No. 3 sample Number 4 thread taper 3:16 1:16 1:12 1:12 tilt angle of the support face of the thread thread profile -4 ° -4 ° -3 ° -3 ° angle of inclination of the embedded face of the thread thread profile 24 ° 24 “ 5" 5 ° angle of inclination of persistent end surfaces of the internal sealing unit 90 ° 90 “ 90 ° 90 ° the angle of inclination of the radial surfaces of the inner sealing unit (covering / covered elements) 273 “ 273 ° 2.39 ° 2.39 ° angle of inclination of persistent end surfaces of the external sealing assembly (female / male elements) 14715 ° 14715 ° 15 ° 15 ° the angle of inclination of the radial surfaces of the outer 10 ° 10" - - sealing unit thread cut length of male element thirty% thirty% - - cutting height of the male element 40% 40% - - Gas tightness test results one hundred%* one hundred%* 0% * 0% * Make-up test results h ** 3 ** I * * I **

* gas tightness index obtained during testing of samples (100% - total gas tightness of the compound, 0% - lack of gas tightness);

** the number of screwing-unscrewing, which withstood the samples in the absence of damage (scoring) of the surfaces of the sealing units and threads.

Thus, samples No. 1, 2, made in accordance with the claimed invention, showed the gas tightness of the compound under the action of tensile, compressive and bending loads, torque in various combinations thereof, improving the screwing characteristics of the compound.

Claims (3)

CLAIM 1. A tight threaded connection of casing pipes containing male and female elements, at the ends of which on the outer and inner surfaces, respectively, are made of trapezoidal tapered threads and forming internal and external sealing units contacting contact end and radial sealing surfaces, while A circumferential groove is made on the female element at the thread exit, characterized in that the persistent trapezoidal threads of the male and female elements made with a taper of 1:16, the angle of inclination of the embedded edge of the thread profile of 10-30 ° to the normal of the axial line of the thread and the angle of inclination of the reference face of the profile of the thread from 0 to -10 ° to the normal of the axial line of the thread, the external sealing assembly is formed by radial sealing surfaces of the male and female of female elements made at an angle of 7-12 ° to the axial line of the thread, and persistent end surfaces of male and female elements made at an angle of 5-17 ° to the normal of the axial line of the thread, provided that the angle of inclination of the emphasis is exceeded end surface of the male element above the angle of inclination of the thrust end surface of the female element, the internal sealing unit is formed by radial sealing surfaces of the male and female elements, made at an angle of 1.5-4.0 ° to the axial line of the thread, provided that the angle of inclination of the sealing surface of the male element above the angle of inclination of the sealing surface of the female element, while at a length equal to 20-40% of the total length of the thread made on male starting from the thread entry, the specified thread was pumped with a decrease in its height to 50% of the total thread profile height of the covered element, and on the covering element, the transition from the radial sealing surface to the surface of the circumferential groove is made spherical. 2. The compound according to claim 1, characterized in that the circumferential groove at the thread exit of the female element has a triangular profile. 3. The compound according to claim 1, characterized in that the radius of the sphere along which the transition from the radial sealing surface of the enclosing element to the surface of the circumferential groove is made is 1-3 mm.