EA031821B1 - Sealed threaded joint for casing pipes - Google Patents

Abstract

The joint consists of the male and female elements with trapezoidal tapered threads with 1:16 taper performed correspondingly on the external and internal surfaces of its ends. Load flank inclination angle of the thread profile of the male and female elements is 2-4° to the thread axes normal line and lead-in flank inclination angle of the thread profile is 9-11° to the thread axes normal line. The joint is performed with inner sealing unit, formed by intercontacting bearing end surfaces located perpendicularly to the thread axis line. The bearing end length of the male element is 6.9-100.3 mm and is in direct relation to the gap width (Δ1) on the thread profile lead-in flank and in inverse relation to the male element yield point. High sealability of the joint under sufficient multidirectional loads applied is preserved as well as high durability of the joint, its improved make-up features, internal casing pipes string flushness are obtained.

Description

The invention relates to a high-pressure threaded connections of casing and can be used to connect the elements of casing strings used in the construction and operation of oil and gas wells.

Casing oil and gas wells are operated in difficult conditions in the presence of corrosive working environments and with significant multidirectional mechanical loads. In this regard, the main requirements for casing pipes are their high wear resistance during repeated screwing-up and uncoupling and operation of the joint, preservation of tightness under high mechanical loads.

In the prior art, a threaded connection of casing pipes is known, which includes male and female elements, at the ends of which, on the outer and inner surfaces, respectively, persistent trapezoidal tapered threads are made (GOST R 51906-2002, pp. 17-19 (1)).

The threaded connection of the casing, disclosed in document (1), has the disadvantage of poor joint bondability characteristics - the difficulty of controlling a given amount of tension and torque in the process of screwing the joint. The difficulty of establishing the necessary amount of tension leads to a low-twist or twisted connection. Under-twisting of the joint leads to a significant drop in its tightness; with twisting, the contact surfaces of the joint can be damaged, which reduces the wear resistance of the joint when it is screwed and unscrewed repeatedly.

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

In addition, the specified threaded connection does not ensure the uniformity of the casing string, which affects the free, without jamming, the passage of equipment, tools on the column during the construction and operation of wells, as well as on the formation of disturbance of the flow of the working medium inside the column, leading to the formation of local high pressure zones.

This technical solution (1) is taken as a prototype of the claimed invention.

The task to which the claimed invention is directed is the creation of a threaded joint of casing pipes with high tightness, improved screwing characteristics and equal passability with ease of manufacture, operation and ensuring screwing of the claimed connection without using adapters with other connections with resistant trapezoidal tapered threads such as the Buttress , OTTM, OTTG, WARM.

The technical result provided by the claimed invention, is to provide a high tightness of the connection under the action of significant multidirectional loads (tension, compression, bending), the wear resistance of the connection, its improved characteristics of screwing, internal equiprocession of the casing string.

The high-pressure threaded connection of the casing contains male and female elements, at the ends of which on the outer and inner surfaces, respectively, are made of resistant trapezoidal tapered threads with a taper of 1:16. The angle of inclination of the support face of the thread coil profile 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 edge of the thread coil profile is 9-11 ° to the normal of the axial line of the thread. In addition, the connection is made with an internal sealing unit formed by contacting end abutment surfaces in contact with and covering the elements and located perpendicular to the axial line of the thread. The length of the thrust end of the male element is 6.9-100.3 mm.

FIG. 1 shows the threaded connection of the casing in a screwed-up condition and the profile of the thread coil;

in fig. 2 - threaded connection of casing in a screwed-up condition and internal sealing unit.

The high-pressure threaded connection of the casing contains a male (2) and female (1) elements, at the ends of which, on the outer and inner surfaces, respectively, there are persistent conical trapezoidal threads (3).

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

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

Under the normal axis of the axial line of the thread refers to the perpendicular, held to the axial line of the thread.

The implementation of the angle of inclination of the embedded face (6) of the thread coil profile (3) of 9-11 ° to the normal of the axial line of the thread stabilizes the position of the male element (2) relative to the female

- 1 031821 th element (1) at the initial stage of screwing the joint, which prevents the joint from jamming and damaging the surfaces of the threads of the threads (3) (tearing) and provides for the possibility of multiple knotting and splitting of the joint and its high tightness.

The implementation of the angle of inclination of the support face (7) of the thread coil profile (3) of 2-4 ° to the normal axis of the thread line ensures that the threads of the threads (3) do not get out of engagement with each other with significant tensile loads (loss of tightness) affecting the connection under the action of the own weight of the column, lowered into the well.

Also, the above angles of inclination of the mortgage (6) and supporting (7) faces of the thread turn profile (3) provide the possibility of screwing the claimed connection with a wide range of other threaded connections of casing pipes with trapezoidal threads, i.e. it is possible to assemble the elements of the column without the use of special subs.

The connection is made with an internal sealing unit (4) formed by contacting end faces (5) in contact with each other. At the same time, said stop end surfaces (5) of the male (2) and female (1) connecting elements are located perpendicular to the axial line of the thread.

The presence in the joint of the sealing unit (4) makes it possible to increase the tightness of the joint due to the fact that when screwing the joint, the thrust end surfaces (5) that are in contact with each other with significant contact stresses, which ensure the occurrence of elastic deformations of the surfaces (5), form a metal-to-metal seal and provide high tightness of the connection under the action of multidirectional loads.

Also, due to the presence of an internal sealing unit (4) and, accordingly, two contacting end faces (5), precise positioning of the male (2) and female (1) elements relative to each other is ensured, an increased moment of connection screwing up, precise fixation of a given value tension and torque in the process of screwing the connection, i.e. improved screwing characteristics, ability to control the screwing of the compound. In addition, it provides increased resistance to compressive loads and torque arising from the operation of the connection.

Internal uniformity (closure of the internal contour of the male 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 thrust end surfaces (5) of the male (2) and female (1) connecting elements perpendicular to the axial line of the thread improves the wear resistance of the connection. Thrust conical trapezoidal threads (3) are characterized by the absence of a gap along the tops of the profile of the thread (8) of the male (2) and female (1) elements (the profile is equally high). When screwing a joint having perpendicular to the axial line of the thread, resistant end surfaces (5), when the surfaces (5) are closed and the connection is further tightened, there is no vertical component of the impact force, which prevents surface damage to the tops of the thread turn profile (8), scoring on them and thereby increasing the wear resistance of the joint as a whole.

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

The length of the stop end (L) in this case means the distance from the stop end surface (5) of the male (2) element to the end of the chamfer of the first thread (3) of the male (2) element in the engagement (Fig. 2).

In each case, the length of the stop end (L) of the male element (2) is selected from the specified interval depending on the gap width (Δ1) along the mortgage face (6) of the thread coil profile (3) (direct relationship) and the yield strength of the material covered (2 a) element (inverse relationship).

When screwing the joint, the thrust end surfaces (5) are closed and, with further tightening, the joints are deformed in the area of elastic deformations. It is important that this deformation of the surface (5) remains in the area of elastic deformations and does not go into the area of plastic deformations that cause damage to the surfaces (5), scoring on them and, as a consequence, a decrease in the wear resistance of the compound during its repeated screwing-unscrewing.

At the request of GOST standards operating in the specified field of technology, the covering element (1) is always made of a stronger material than the male element (2). Thus, all calculations for the possible deformation of the thrust end surfaces (5) are carried out by the covered element (2).

First of all, preventing the transition of the deformation of the surface (5) of the male element (2) from the elastic to the plastic region depends on the yield strength of the material from which the male 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 thrust end (L) will prevent such a transition.

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In addition, the thrust tapered trapezoidal threads (3) have a constructive gap (Δ1) on the embedded faces (6) of the coil profile, which is necessary for free, without jamming, screwing of this type of threads. When screwing the joint after closing the stop end surfaces (5), which perceive the compressive load from this moment on and, accordingly, are deformed, the gap along the mortgage faces (6) of the coil profile is gradually selected and then the clamped faces (6) assume the compressive load, preventing the transition of the deformation of the thrust end surface (5) of the male element (2) into the plastic deformation region. Those. the larger the gap (Δ1) along the embedded faces (6) of the thread turn profile (3), the greater the length of the stop end (L) is needed to ensure that the deformation of the surface (5) of the male element (2) does not become plastic.

When performing the thrust end of the male element (2) with a length (L) less than 6.9 mm, the surface deformation (5) of the male element (2) is transferred from the elastic region to the plastic deformation region, irreversible damage to the surface (5) of the male element (2) , scoring, which will reduce the wear resistance of the compound and its tightness.

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

An example embodiment of the invention

The claimed connection, consisting of male and female elements, is made with resistant trapezoidal tapered threads with a taper of 1:16. The angle of inclination of the support face of the thread coil profile is 3 ° to the normal of the axial line of the thread, and the angle of inclination of the embedded face of the thread coil profile is 10 ° to the normal of the axial line of the thread. 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 assembly formed by contacting end abutment surfaces in contact with each other, located perpendicularly to the axial line of the thread. The length of the thrust end of the male element was selected from the stated interval depending on the gap width along the embedded face of the thread turn profile and the yield strength of the material of the male element (see table).

No material yield strength of the covered element, MPa gap width (Δ1) along the embedded edges of the joint, mm the length of the thrust end (L) of the male element, mm technical result provided one 379 0.03 15.8 Tests of compounds containing 2 0.10 52,8 the signs mentioned above and 3 0.19 100.3 shown in the table showed a complete hernia four 621 0.03 9.7 ticity when applying various five 0.10 32.2 directional loads and lack 6 0.19 61.2 wear surfaces of joints, in 7 862 0.03 6.9 particular damage resistant eight 0.10 23.2 target surfaces, at 3x 9 0.19 44.0 screwing-unscrewing the connection ten 379 0.10 6.0 Tests have shown damage to the thrust end surfaces. 12 862 0.10 6.0 after a single screwing, unscrewing the joint

Claims (1)

CLAIM High-tight threaded connection of casing, containing male and female elements, at the ends of which, on the external and internal surfaces, respectively, persistent trapezoidal tapered threads are made, characterized in that the resistant trapezoidal tapered threads of the male and female elements are made with a taper of 1:16, the angle of the bearing face coil profile 2-4 ° to the normal axis of the axial line of the thread and the angle of inclination of the embedded side of the profile of the coil 9-11 ° to the normal of the axial line of the thread, while the connection in Made with an internal sealing assembly formed by contacting end faces that are in contact with the male and female elements and located perpendicular to the axial line of the thread, the length of the male end of the male element is 6.9100.3 mm and is directly dependent on the width of the gap ( Δ1) on the embedded edge of the thread turn profile and in inverse relation to the yield strength of the material of the male element. - 3 031821