RU2504710C1 - Sealed threaded connection of casing pipes (versions) - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: connection includes male and female elements, on the ends of which there are thrust trapezoid-shaped threads on outer and inner surfaces respectively, which have obliquity of 1:16, an inclination angle of a support edge of turn profile of 2-4° to the normal of an axial thread line and an inclination angle of a captivating edge of turn profile of 9-11° to the normal of the thread axial line. The connection has an internal sealing assembly formed with thrust end surfaces contacting to each other and located perpendicular to the thread axial line. Length of the thrust end of the male element is 6.9-100.3 mm. A version of a connection configuration is described.

EFFECT: tightness of the connection at interaction of considerable differently directed loads, and wear resistance of the connection.

2 cl, 2 dwg, 1 tbl

Description

The claimed invention relates to highly leak-proof threaded joints of casing pipes and can be used to connect elements of casing columns used in the construction and operation of oil and gas wells.

Casing pipes of oil and gas wells are operated in difficult conditions in the presence of aggressive working environments and with significant multidirectional mechanical loads. In this regard, the main requirements for casing pipes are their high wear resistance with repeated screwing-unscrewing and operation of the connection, maintaining tightness at high mechanical loads.

A threaded connection of casing pipes is known from the prior art, containing male and female elements, at the ends of which on the outer and inner surfaces, respectively, made resistant trapezoidal tapered threads (GOST R 51906-2002, p. 17-19 (1)).

The threaded connection of casing pipes disclosed in document (1) has the disadvantage of poor characteristics of make-up of the connection - the difficulty of controlling the set value of the interference fit and torque in the process of making-up of the connection. The difficulty in establishing the necessary amount of interference leads to incompleteness or twist of the connection. The untwisted connection leads to a significant drop in its tightness, when twisted, the contact surfaces of the connection can be damaged, which reduces the wear resistance of the connection with repeated screwing-unscrewing.

Also, the necessary level of tightness of the connection is not provided, which is necessary during the operation of casing pipes, due to the presence of structural and technological gaps in the persistent trapezoidal tapered threads.

In addition, the specified threaded connection does not provide equidistant casing string, which affects the free, without jamming, passage of equipment, tools through the string during construction and operation of wells, as well as the formation of disturbances in the flow of the working medium passing inside the string, leading to the formation of local high pressure zones.

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, improved make-up characteristics and equidistance with ease of manufacture, operation and provision of make-up of the claimed connection without the use of adapters with other joints with persistent trapezoidal tapered threads, such as Butress , OTM, OTTG, WARM.

The technical result provided by the claimed invention is to provide high tightness of the joint when exposed to significant multidirectional loads (tension, compression, bending), wear resistance of the joint, its improved make-up characteristics, internal equal bore of the casing string.

The highly tight threaded connection of the casing pipes includes male and female elements, at the ends of which on the outer and inner surfaces, respectively, resistant trapezoidal tapered threads with a taper of 1:16 are made. The angle of inclination of the reference face of the thread profile of the threads of the male and female elements is 2-4 ° to the normal of the axial line of the thread, and the angle of inclination of the embedded face of the profile of the thread of the thread is 9-11 ° to the normal of the axial thread line. In this case, the connection is made with an internal sealing unit formed by contacting thrust end surfaces made on male and female elements and located perpendicular to the axial line of the thread. The length of the persistent end of the male element is 6.9-100.3 mm.

Another embodiment of the claimed invention is a high-tight threaded connection of casing pipes containing 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 reference face of the thread profile of the thread of the male and female elements is -3 - -5 ° to the normal of the axial line of the thread, and the angle of inclination of the embedded face of the profile of the thread of the thread is 23-25 ° to the normal of the axial thread line. In this case, the connection is made with an internal sealing unit formed by contacting thrust end surfaces made on male and female elements and located perpendicular to the axial line of the thread. The length of the persistent end of the male element is 6.9-100.3 mm.

Figure 1 shows the threaded connection of the casing in the screwed-up state and the profile of the thread.

Figure 2 shows the threaded connection of the casing in the screwed state and the internal sealing unit.

The high-tight threaded connection of the casing pipes includes male (2) and female (1) elements, on the ends of which on the outer and inner surfaces, respectively, made resistant conical trapezoidal threads (3).

Thrust trapezoidal tapered threads (3) on male (2) and female (1) elements are made with a taper of 1:16. The execution of threads (3) with a taper of 1:16 provides a high degree of their engagement with each other in a screwed state and the possibility of optimal perception by the connection of bending and tensile loads acting during operation of the connection.

The angle of inclination of the embedded face (6) of the thread twist profile (3) of the male (1) and female (2) elements is 9-11 ° to the normal of the axial thread line, and the angle of inclination of the support face (7) of the thread twist profile (3) is 2 -4 ° to the normal to the center line of the thread.

By the normal of the centerline of the thread is meant the perpendicular drawn to the centerline of the thread.

Performing the inclination angle of the embedded face (6) of the thread turn profile (3) equal to 9-11 ° to the normal of the center line of the thread stabilizes the position of the male element (2) relative to the female element (1) at the initial stage of screwing the joint, which prevents the joint from sticking and surface damage threads (3) (seizure) and provides the possibility of multiple paging-demining of the connection and its high tightness.

The execution of the angle of inclination of the support face (7) of the thread twist profile (3) equal to 2-4 ° to the normal of the axial thread line eliminates the possibility of thread threads (3) coming out of engagement with each other under significant tensile loads (loss of tightness) affecting the connection under the influence of the own weight of the column lowered into the well.

Also, the aforementioned inclination angles of the embedded (6) and supporting (7) faces of the thread thread profile (3) make it possible to make the claimed connection with a wide range of other threaded joints of casing pipes with trapezoidal threads, that is, it is possible to assemble the elements of the string without using special adapters.

Another embodiment of the claimed invention is characterized by the execution of the angle of inclination of the embedded face (6) of the thread coil profile of the male (2) and female (1) threads 23-25 ° to the normal of the axial line of the thread and the angle of inclination of the reference face (7) of the thread thread profile can be from -3 to -5 ° to the normal to the center line of the thread.

The main function of such a thread is the perception of tensile and bending loads that occur during operation of the joint.

A negative angle (-3 to -5 °) of the inclination of the support face (7) of the thread twist profile (3) excludes the possibility of the threads of the male and female elements coming out of engagement with each other under significant tensile loads. A reduction in the radial interference in the thread is also achieved in comparison with the designs of threads having a positive angle of the support face, which ensures high wear resistance of the joint, improves its performance under increased loads.

The implementation of the angle of inclination of the embedded face (6) of 23-25 to the normal of the axial line of the thread facilitates the screwing of the connection and increases its wear resistance with repeated screwing-unscrewing.

Also, the aforementioned inclination angles of the embedded (6) and supporting (7) faces of the thread coil profile (3) make it possible to make the claimed connection with a wide range of other threaded joints of casing pipes with trapezoidal threads, that is, it is possible to assemble the elements of the string without using special adapters.

The connection is made with the internal sealing unit (4), formed by contacting each other thrust end surfaces (5). Moreover, these thrust end surfaces (5) of the male (2) and female (1) connection elements are perpendicular to the axial line of the thread.

The presence of a sealing assembly in the connection (4) allows to increase the tightness of the connection due to the fact that when making the connection, the persistent end surfaces (5) in contact with significant contact stresses that ensure the emergence of elastic deformations of the surfaces (5) form a metal-type seal metal ”and provide high tightness of the connection under the action of multidirectional loads.

Also, due to the presence of an internal sealing assembly (4) and, accordingly, two contacting end face surfaces (5) that are in contact with each other, precise positioning of the male (2) and female (1) elements relative to each other, the increased make-up moment of the joint, and precise fixation are ensured a given amount of interference and torque during the make-up process of the joint - that is, improved make-up characteristics, the ability to control the make-up of the joint. In addition, it provides increased resistance of the connection to compressive loads and torque arising from the operation of the connection.

Internal equidistance (isolation of the inner contour of the covered element, column), provided by the presence in the connection of the internal sealing unit (4), increases the operational efficiency of the connection.

The implementation of the persistent end surfaces (5) of the male (2) and female (1) connection elements perpendicular to the axial line of the thread increases the wear resistance of the connection. Persistent tapered trapezoidal threads (3) are characterized by the absence of a gap along the vertices of the thread thread profile (8) of the male (2) and female (1) elements (the profile is equally high). When making up a connection having persistent end surfaces (5) perpendicular to the axial line of the thread, when closing the surfaces (5) and further tightening the connection, there is no vertical component of the force of action, which prevents surface damage to the vertices of the thread thread profile (8), the formation of burrs on them, and thereby increasing the wear resistance of the compound as a whole.

The length of the thrust end (L) of the male element (2) is 6.9-100.3 mm.

In this case, the length of the thrust end (L) means the distance from the thrust end surface (5) of the male (2) element to the end of the chamfer of the first thread thread (3) of the male (2) element in engagement (FIG. 2).

In each case, the length of the thrust end (L) of the male element (2) is selected from the specified interval depending on the gap width (Δl) according to the embedded face (6) of the thread thread profile (3) (direct dependence) and the yield stress of the material covered (2 ) element (inverse relationship).

When making the connection, the persistent end surfaces (5) are closed and upon further tightening the connections are deformed in the region of elastic deformations. It is important that the specified surface deformation (5) remains in the region of elastic deformations and does not go into the region of plastic deformations that cause damage to surfaces (5), the formation of scoring on them, and as a result, a decrease in the wear resistance of the joint when it is repeatedly screwed-unscrewed.

At the request of GOSTs operating in the indicated field of technology, the covering element (1) is always made of a more durable material than the covered element (2). Thus, all calculations of the possible deformation of the persistent end surfaces (5) are carried out on the covered element (2).

First of all, the prevention of the transition of deformation of the surface (5) of the covered element (2) from elastic to plastic region depends on the yield strength of the material from which the covered element (2) is made. The greater the strength and, accordingly, the yield strength of the material from which the male element (2) is made, the shorter the length of the thrust end (L) will prevent such a transition.

In addition, persistent tapered trapezoidal threads (3) have a structural gap (Δl) along the embedded edges (6) of the thread profile necessary for free, without jamming, screwing of this type of thread. When making up the connection after closing the persistent end surfaces (5), which perceive, starting from this moment, the compressive load and, accordingly, are deformed, the gap along the embedded edges (6) of the coil profile is gradually selected and then the embedded edges (6) take on the compressive load , preventing the transition of deformation of the persistent end surface (5) of the male element (2) into the region of plastic deformation. That is, the larger the gap (Δl) along the embedded edges (6) of the thread twist profile (3), the greater the length of the thrust end (L) is necessary to ensure that the deformation of the surface (5) of the covered element (2) does not go into the plastic region.

When performing the persistent end of the male element (2) with a length (L) of less than 6.9 mm, the surface deformation (5) of the male element (2) undergoes a transition from the elastic region to the plastic deformation region, irreversible damage to the surface (5) of the male element (2) , the formation of scoring, which will entail a decrease in the wear resistance of the joint and its tightness.

The implementation of the persistent end of the male element (2) with a length (L) of more than 100.3 mm is impractical, since the specified value of the length (L) ensures that the surface deformation (5) is in the elastic region and exceeding the length (L) of more than 100.3 mm gives only an increase in the complexity of the manufacturing process of the compound.

Examples of carrying out the invention.

1. The claimed connection, consisting of male and female elements, made with persistent trapezoidal tapered threads with a taper of 1:16. The angle of inclination of the reference face of the thread coil profile is 3 to the normal of the axial thread line, and the angle of inclination of the embedded face of the thread thread profile is 10 ° to the normal of the axial thread line. The thread pitch is 5.08 mm with a nominal thread diameter of 245 mm and a wall thickness of 8.94 mm. The connection is made with an internal sealing unit formed by contacting thrust end surfaces located perpendicular to the axial line of the thread. The length of the thrust end of the male element was selected from the declared interval, depending on the width of the gap along the embedded edge of the thread thread profile and the yield strength of the material of the male element (see Table 1).

Table 1 No. The yield strength of the material of the covered element, MPa The width of the gap (Δl) on the embedded edges of the connection, mm The length of the thrust end (L) of the male element, mm Provided technical result one 379 0,03 15.8 Tests of the joint containing the characteristics indicated above and given in the table showed complete tightness when applying differently directed loads and the absence of wear of the surfaces of the joint, in particular damage to the persistent end surfaces, with 3-fold screwing-unscrewing of the joint 2 0.10 52.8 3 0.19 100.3 four 621 0,03 9.7 5 0.10 32,2 6 0.19 61.2 7 862 0,03 6.9 8 0.10 23,2 9 0.19 44.0 10 379 0.10 6.0 The tests showed damage to the persistent end surfaces after a single make-unscrew connection 12 862 0.10 6.0

2. The claimed connection, consisting of male and female elements, made with persistent trapezoidal tapered threads (3) with a taper of 1:16. The angle of inclination of the reference face of the thread thread profile is -4 ° to the normal of the axial line of the thread, and the angle of inclination of the embedded face of the thread thread profile is 24 ° to the normal of the axial thread line. The thread pitch is 5.08 mm with a nominal thread diameter of 245 mm and a wall thickness of 8.94 mm. The connection is made with an internal sealing unit formed by contacting thrust end surfaces located perpendicular to the axial line of the thread. The length of the thrust end of the male element was selected from the declared interval, depending on the width of the gap along the embedded edge of the thread thread profile and the yield strength of the material of the male element in the same manner as in example 1 (see table 1).

Tests of the compound made as described in Example 2 showed the same results as the tests of the first sample.

Claims (2)

1. Highly tight threaded connection of casing pipes containing male and female elements, at the ends of which on the outer and inner surfaces respectively made thrust trapezoidal conical threads, characterized in that the thrust trapezoidal conical threads of the male and female elements are made with a taper of 1:16, the angle of inclination the reference face of the thread profile 2 ° -4 ° to the normal of the axial line of the thread and the angle of inclination of the embedded side of the profile of the thread 9 ° -11 ° to the normal of the axial line of the thread, This is done with an internal sealing assembly formed by contacting thrust end surfaces made on the male and female elements and located perpendicular to the axial line of the thread, the length of the thrust end of the male element being 6.9-100.3 mm. 2. Highly tight threaded connection of casing pipes containing male and female elements, at the ends of which on the outer and inner surfaces respectively there are thrust trapezoidal tapered threads, characterized in that the thrust trapezoidal tapered threads of the male and female elements are made with a taper of 1:16, the angle of inclination the reference edge of the thread profile is -3 ° - -5 ° to the normal of the axial line of the thread and the angle of inclination of the embedded edge of the profile of the thread is 23 ° -25 ° to the normal of the axial line of the thread, ix formed with internal sealing assembly formed by a thrust between the contacting end faces formed on the male and female elements and disposed perpendicular to the axial line of the thread, the length of the bearing end of the male member is 6,9-100,3 mm.

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