GB2104990A

GB2104990A - A tubular coupling for lining a well wall

Info

Publication number: GB2104990A
Application number: GB08125759A
Authority: GB
Inventors: John-Herbert North
Original assignee: DRILLCON IND Ltd
Current assignee: DRILLCON IND Ltd
Priority date: 1981-08-24
Filing date: 1981-08-24
Publication date: 1983-03-16
Also published as: IN157701B; ES515225A0; ES8308387A1; BR8204950A; KR840001673A; JPS5841182A; CA1205837A; AU8753982A; GB2104990B

Abstract

A tubular coupling comprises a male threaded section 16 and a female threaded section 14. The female threaded section 14 has a shoulder 18 at the base of its thread 20 and the shoulder 18 is engaged by an abutment 22 on the male threaded section 16, when the sections 14 and 16 are fully engaged, to thereby provide a seal. The shoulder 18 is under cut and the abutment 22 is complementarily shaped whereby, upon application of a lateral bending moment to the coupling, a radial force is produced between the shoulder 18 and abutment 22 in order to maintain the seal. There is also provided a sleeve for lining a well wall comprising sleeve sections and tubular couplings for interconnecting the sleeve sections. The sleeve sections may be formed by friction forging a coupling component to each end of a central tubular member (12), wherein the coupling components are preferably components of the tubular coupling outlined above. <IMAGE>

Description

SPECIFICATION A sleeve for lining a well wall and a tubular coupling therefore The present invention relates to a sleeve for lining a well wall and a tubular coupling therefore.

When a well is drilled, particularly for oil wells, the wall of the well is lined with a sleeve which is formed of tubular sections which are screwthreaded together as the sleeve is inserted into the well. The tubular sections are conventionally manufactured from lengths of tubing the ends of which are upset forged and subsequently cold rolled in order to provide the threads for engaging one tubular section to the next.

The present invention seeks to provide an improved sleeve for lining a well wall and an improved tubular coupling for use in connecting together the tubular sections of the sleeve.

According to a first aspect of the present invention, there is provided a tubular coupling comprising a male threaded section and a female threaded section, the female threaded section having a shoulder at the base of the thread, the shoulder being engaged by an abutment on the male threaded section, when the sections are fully engaged, to thereby provide a seal, the shoulder being undercut and the abutment being complementarily shaped whereby, upon application of a lateral bending moment to the coupling a radial force is produced between the shoulder and abutment in order to maintain the seal.

According to a second aspect of the present invention, there is provided a sleeve section for forming a sleeve for lining a well wall, comprising a central tubular member having a respective coupling component friction forged to each end thereof.

Preferably, the threads of the male and female sections are provided on respective frusto-conical surfaces.

Advantageously, the male threaded section is provided with a shoulder at the base of the thread and the female threaded section is provided with a complementarily shaped abutment whereby, upon application of a lateral bending moment to the coupling a portion of the female threaded section abutment may engage a portion of the male threaded section shoulder.

According to a further aspect of the present invention there is provided a method of manufacturing a sleeve section for forming a sleeve for lining a well wall comprising friction forging a respective coupling component with each end of a central tubular member.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic partial side view of the ends of two sleeve sections coupled together, Figure 2 is a longitudinal sectional view of part of a tubular coupling used for connecting together sleeve sections as shown in Figure 1, Figure 3 illustrates area A of Figure 2 to an enlarged scale, and Figure 4 illustrates area B of Figure 2 to an enlarged scale.

A sleeve for lining a well wall is formed from a number of sleeve sections coupled together. The sleeve sections may be provided with either male or female couplings at both ends, in which case additional components are required for interconnecting the sections, or the sleeve sections may be provided with a female component at one end and a male component at the other end. As can be understood from Figures 1 and 2, the sleeve sections 10 are formed of a central tubular member 12 having a respective coupling component secured to each end thereof.

The central tubular member 12 has a female threaded section 14 friction forged to one end of the central tubular member 12 and a male threaded portion 16 friction forged to the other end thereof.

The male section 14 and the female section 16 may be sequentially friction forged to the central member 12 or, with aid of suitable machinery may be simultaneously friction forged to the central member 12. In either case, the central member 12 is held stationary and the male/female section retained in a chuck. The chuck is revolved at high speed and the male/female section and the central member 12 are brought into contact under the action of a relatively high pressure. The friction between the components is sufficient to cause the components to fuse together. A certain amount of flash may be produced at the junctions of the components and this is subsequently machined off. It has been found possible to produce friction forged adhesion between components wherein the adhesion is stronger than one of the parent materials.

The male and female sections are preformed and hence the sleeve section 10 may easily be constructed having different combinations of coupling sections. The provision of the threaded sections in the conventional manufacture of sleeve sections is burdensome because the entire sleeve section has to be manipulated and machine controlled during formation of the couplings. Conventional manufacture becomes more onerous where specialised couplings or combinations are required and the necessary apparatus is considered to be relatively expensive and slow in operation compared with the method of manufacture of the present invention. The length of the sleeve section 10 is readily variable, since differing lengths of the central tubular member 12 are easily incorporated into the sleeve section 10.

Since the sleeve section 10 is constructed from separate components, the components need not consist of the same material, unlike conventional sleeve sections. The process of friction forging enables materials such as aluminium and steel to be joined even though such joints are generally regarded as being unobtainable by known methods of welding. In the known art, if it is desired to provide couplings of a high quality material, then the entire sleeve section 10 must necessarily be formed of that material. The present invention permits a lower quality material to be used for the major, central, member 12 and a different material having the requisite qualities to be used for the coupling components 14 and 16. It is often acceptable to have a central member 12 of the sleeve section 10 fabricated from a different quality material than the coupling components 14 and 16.This is due to the fact that the coupling components threadedly engage like components and are subjected to rotary torques during assembly of the sleeve sections to form a sleeve for lining a well wall. The central member 12 is not subjected to any substantial rotary torque during assembly of the sleeve section into a sleeve. It has been found that the sleeve sections 10 of the present invention readily meet the industrial strength standards specified for such components. An additional benefit of forming the sleeve sections 10 of discrete components is that the central member 12 can be pretreated, for example by being provided with a coating. Such coatings may be applied for a specific purpose such as anticorrosion. This feature can be of particular benefit when the central member 12 is fabricated of a lower quality material than the coupling sections 14 and 16.

Sleeve sections 10 of the present invention are economically desirable since they may permit the raw material cost to be reduced and permit the speed of manufacture to be improved. The combined time for preforming the coupling sections 14 and 16 and the central member 12 and subsequently friction forging the components together is enhanced with respect to the conventional manufacturing process involving upset forging of the ends of a sleeve section.

Improved alignment between the axis of the coupling sections can accrue from the use of the friction forging process.

The tubular coupling used for interconnecting the sleeve sections 10 comprises the female threaded section 14 and the male threaded section 16, as can be seen in Figure 2. The threads of these sections 14, 16 are provided on frusto-conical surfaces and such an arrangement is sometimes referred to as "an extreme line thread". The female section 14 has a shoulder 18 at the base of the thread 20. The male threaded section 16 has an abutment 22 which engages with the shoulder 18 when the male and female sections 14, 16 are fully engaged. Engagement of the shoulder 18 by the abutment 22 provides a fluid tight seal preventing the escape of fluid flowing within the sleeve by penetration through the coupling.

The shoulder 1 8 of the female threaded section 14 is under cut and the abutment 22 of the male threaded section 16 is comlementarily shaped to fit into the under cut shoulder 18. The engagement between the male abutment 22 and the female under cut shoulder 18 is shown on an enlarged scale in Figure 3. The inclined surface 24 of the under cut shoulder 18 mates with a surface 26 of the abutment 22 which is inclined at the same angle as the surface 24.The inner upright 28 of the shoulder 18 mates with a surface 30 on the abutment 22. The upright 28 of the shoulder 18 is offset from the surface 32 on which the thread 20 is provided in order that the surface 30 of the abutment 22 may readily pass over the thread 20 but still mate with the surface 28.

Consequently, in addition to the seal provided by the engagement of the respective threads of the male and female sections two additional seals are provided. One of the additional seals being the engagement of surface 24 with surface 26 and the other being the engagement between surfaces 28 and 30. If the tubular coupling is subjected to a lateral bending moment, during installation of the sleeve or due to movement of the well wall, at least one of the additional seals is maintained on either side of the coupling. If a lateral bending moment is applied in the direction indicated by arrow C in Figure 2, a radial force will be generated which will tend to separate surfaces 28 and 30 on the side of the coupling illustrated in Figures 2 and 3 while reinforcing the contact between surfaces 28 and 30 on the opposite (unillustrated) side of the coupling.This could result in the seal being broken for part of the circumference of the coupling. However, for that part of the circumference of the coupling in which the surfaces 28 and 30 are urged apart the surfaces 24 and 26 must necessarily be urged into harder engagement. Therefore, a circumferential seal is maintained between the abutment 22 and shoulder 18 when a lateral bending moment is applied to the coupling.

The angle of inclination of the inclined surface 24 of the under cut shoulder 1 8 with respect to the longitudinal axis of the sleeve section 10 is preferably of the order of 450, although the precise angle is not critical.

The male threaded section 16 is provided with a shoulder 34 at the base of the male thread 36.

The female threaded section 14 is provided with an abutment 38 which abuts the shoulder 34. The shoulder 34 is undercut and the abutment 38 is complementarily shaped so that the abutment 38 and shoulder 34 engage in a similar fashion to the abutment 22 and shoulder 18. However, the upright 40 of the shoulder 34 is not offset from the thread level as is the upright 28 of the shoulder 18 In addition, a small clearance typically of the order of two thousandths of an inch may be left between the abutment 38 and shoulder 34 so as to ensure that surfaces 24 and 26 of the shoulder 18 and abutment 22 respectively are not prevented from mating by the prior mating of abutment 38 and shoulder 34.

Claims

1. A tubular coupling comprising a male threaded section and a female threaded section, the female threaded section having a shoulder at the base of the thread, the shoulder being engaged by an abutment on the male threaded section, when the sections are fully engaged, to thereby provide a seal, the shoulder being under cut and the abutment being complementarily shaped whereby, upon application of a lateral bending moment to the coupling a radial force is produced between the shoulder and abutment in order to maintain the seal.

2. A tubular coupling as claimed in claim 1, wherein the threads of the male and female sections are provided on respective frusto-conical surfaces.

3. A tubular coupling as claimed in Claim 1 or 2, wherein the angle of the under cut of the shoulder is substantially 450 with respect to the axis of the coupling.

4. A tubular coupling as claimed in any preceding claim, wherein the male threaded section is provided with a shoulder at the base of its thread, the female threaded section having an abutment which is adjacent the shoulder of the male threaded section when the male and female sections are fully engaged, the shoulder of the male threaded section being under cut and the abutment of the female threaded member being complementarily shaped whereby, upon application of a lateral bending moment to the coupling a portion of the abutment on the female threaded section may contact a corresponding portion on the shoulder of the male threaded section.

5. A tubular coupling as claimed in claim 4, wherein the angle of the under cut of the shoulder on the male threaded section is substantially 450 with respect to the longitudinal axis of the coupling.

6. A sleeve section for forming a sleeve for lining a well wall comprising a central tubular member having a respective coupling component friction forged to each end thereof.

7. A sleeve section as claimed in Claim 6, wherein the central tubular member and at least one coupling component are formed of different materials.

8. A sleeve section as claimed in claim 6 or 7, wherein the central tubular member is provided with a coating.

9. A sleeve section as claimed in any of Claims 6 to 8, wherein one of the coupling components is a male member and the other coupling component is a female member.

10. A sleeve section as claimed in any of Claims 6 to 9, wherein the coupling components are provided with threaded portions for effecting coupling.

11. A sleeve section as claimed in Claims 9 and 10, wherein the male member and female member are capable of forming respective tubular couplings with complementary threaded sections of additinoal sleeve sections, the tubular couplings being as claimed in any of Claims 1 to 5.

12. A sleeve for lining a well wall comprcsing a plurality of sleeve sections, the sleeve sections being as claimed in any of Claims 6 to 11.

13. A method of manufacturing a sleeve section for forming a sleeve for lining a well wall comprising friction forging a respective coupling component with each end of a central tubular member.

14. A method as claimed in Claim 13, wherein the coupling components are simultaneously friction forged with the central tubular member.

15. A method as claimed in Claim 13 or 14, wherein the central tubular member is held stationary during friction forging.

16. A method as claimed in any of Claims 13 to 15, comprising the step of preforming at least one of the coupling components by drop forging.

17. A method as claimed in Claim 16, comprising the step of cold rolling a thread on the coupling component subsequent to drop forging and prior to friction forging.

18. A tubular coupling substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.

1 9. A sleeve section for forming a sleeve for lining a well wall substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.

20. A sleeve for lining a well wall substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

21. A method of manufacturing a sleeve section for forming a sleeve for lining a well wall, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.