OCTG PIPE SYSTEM AND METHOD OF MANUFACTURING THEREOF

Abstract

A pipe system for oil country tubular goods (OCTG) and a method of manufacturing the OCTG pipe system is disclosed. The pipe system includes at least one OCTG pipe having a pipe body, the pipe body having at least one connection end formed in unipartite and materially integral manner with the pipe body for coupling to a second OCTG pipe. The OCTG pipe is formed in seamless fashion from a hardenable steel alloy, and the connection end has a yield strength higher than the yield strength of the pipe body.

Claims

1. A pipe system for oil country tubular goods (OCTG), comprising: at least one OCTG pipe having a pipe body, the pipe body having at least one connection end formed in unipartite and materially integral manner with the pipe body for coupling to a second OCTG pipe, the OCTG pipe is formed in seamless fashion from a hardenable steel alloy, and wherein the connection end has a yield strength higher than the yield strength of the pipe body.

2. The OCTG pipe system of claim 1, further comprising a transition section formed between the connection end and the pipe body of the OCTG pipe, wherein the transition section extends with a length (L) of between 10 mm and 300 mm, in a longitudinal direction of the OCTG pipe.

3. The OCTG pipe system of claim 2, wherein the connection end has an outer diameter (Da) which is smaller than or equal to the outer diameter (Da) of the pipe body, and/or wherein the connection end has a wall thickness (W) which is smaller than or equal to the wall thickness (W) of the pipe body.

4. The OCTG pipe system of claim 3, wherein an external thread is cut into a wall of the connection end into an outer shell surface (7).

5. The OCTG pipe system of claim 4, wherein the yield strength of the connection end lies between 800 and 1300 MPa, and the yield strength of the pipe body lies between 500 and 900 MPa, and/or wherein the yield strength of the connection end is at least 10% greater than the yield strength of the pipe body.

6. The OCTG pipe system of claim 5, wherein a pipe connection sleeve is formed from a hardenable steel alloy and has a yield strength of between 800 and 1300 MPa.

7. The OCTG pipe system of claim 6, wherein the yield strength decreases in the transition section from the connection end to the pipe body with a gradient of greater than 10%, the case being that the material structure in the connection end is completely hardened.

8. The OCTG pipe system of claim 7, wherein the connection end extends in the longitudinal direction of the pipe with a length (L) of 200 mm to 500 mm, the thread extending with a length of up to 300 mm, up to 100 mm in the longitudinal direction.

9. A method for producing a unipartite, materially integral and seamless oil country tubular goods (OCTG) pipe having a pipe body and having at least one connection end and composed of a hardenable steel alloy, comprising: providing a seamlessly rolled, cut-to-length pipe, homogeneously warming and quench hardening the pipe, annealing the hardened pipe, wherein a connection end is annealed with a lower intensity than the pipe body, and in the process setting a yield strength of between 800 and 1300 MPa, in the connection end (4) and a yield strength of the pipe body (2) of between 500 and 900 MPa.

10. The method of claim 9, wherein, before the quench hardening or after the quench hardening, an external thread is cut in the region of the connection end.

11. The method of 10, wherein the annealing of the OCTG pipe is performed in a static annealing apparatus or wherein the OCTG pipe is caused to perform a relative movement through an annealing apparatus, it being provided in particular that introduction of heat is performed with different parameters in different length sections in the respective annealing apparatus.

12. The OCTG pipe system of claim 2, wherein the transition section extends with a length (L) of between 50 mm and 200 mm, in a longitudinal direction of the OCTG pipe.

13. The OCTG pipe system of claim 5, wherein the yield strength of the connection end lies between 900 and 1200 MPa, and the yield strength of the pipe body lies between 600 and 800 MPa.

14. The OCTG pipe system of claim 6, wherein a pipe connection sleeve is formed from a hardenable steel alloy and has a yield strength of between 900 and 1200 MPa.

15. The method of claim 9, wherein the process setting a yield strength of between 900 and 1200 MPa, in the connection end and a yield strength of the pipe body of between 600 and 800 MPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0034] FIG. 1 is a side view of an OCTG pipe according to one embodiment of the present invention.

[0035] FIG. 2 is an end view of the OCTG pipe shown in FIG. 1.

[0036] FIG. 3 is a longitudinal sectional view of the OCTG pipe shown in FIG. 1.

[0037] FIG. 4 illustrates an OCTG pipe system.

[0038] FIG. 5 illustrates a static apparatus for the annealing of the OCTG pipe.

[0039] FIG. 6 illustrates an annealing apparatus through which an OCTG pipe is guided.

[0040] In the figures, the same reference designations are used for identical or similar components, even if a repeated description is omitted for reasons of simplicity.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0041] FIG. 1 shows an OCTG pipe 1 having an overall length L. The OCTG pipe 1 has a centrally arranged pipe body 2 and a pair of connection ends 4 each formed at each of the opposing ends 3 of the pipe body 2. The connection ends 4 extend in a longitudinal direction 5 of the OCTG pipe 1 over a partial length of the pipe, identified as length L4, which preferably is 200 mm to 500 mm long. External thread 6 is formed on the connection ends 4. The external thread 6 extends in the longitudinal direction 5. The external thread 6 extends with a length L6 in the longitudinal direction of the OCTG pipe 1. The length L6 is smaller than the length L4. More specifically, the length L6 of the external thread 6 is up to 75 mm in the longitudinal direction 5. The external thread 6 is, alternatively, cut directly into the outer shell surface 7 of the OCTG pipe 1. Consequently, an outer diameter Da of the OCTG pipe 1 is approximately uniform throughout. The same applies to an inner diameter Di illustrated in FIG. 2 and FIG. 3, which is likewise configured to be uniform throughout.

[0042] The inner diameter Di is preferably configured to be uniform throughout. However, the inner diameter Di may be reduced in the region of the ends 3, in particular in the region of the external thread 6. This is realized in particular by way of an upsetting process (not illustrated in detail). Also, the outer diameter Da may be increased in the region of the connection end 4, in particular in the region of the external thread 6 (also not illustrated). Also, a transition section 8 between the connection end 4 and the pipe body 2 is illustrated.

[0043] The transition section 8 likewise extends with a length L8 in the longitudinal direction 5 of the OCTG pipe 1. The length L8 is preferably from 50 mm to 200 mm. The transition section 8 is not readily mechanically identifiable on the pipe 1. The material structure in the region of the connection end 4 has a greater hardness than the material structure of the pipe body 2. In the transition section 8, the material structure transitions from the hard connection end 4 to the relatively soft and ductile pipe body 2.

[0044] FIG. 4 illustrates two OCTG pipes 1, which are coupled to an OCTG pipe connection sleeve 9. The pipe connection sleeve 9 has an outer diameter DaM greater than the outer diameter Da of the respective OCTG pipes 1. In relative terms, however, the outer diameter DaM of the pipe connection sleeve 9 is smaller than the outer diameter of a sleeve known from the prior art.

[0045] FIG. 5 illustrates a static annealing apparatus 10 having multiple induction coils 11, 11a. An OCTG pipe 1 is introduced and is surrounded by the induction coils 11, 11a. The induction coils 11a are arranged at the outer region of the OCTG pipe 1. The induction coils operate with relatively low energy, such that the hardened OCTG pipe 1 is subject to less intense annealing in the region at the ends 3. The transition section is produced in flowing as a result of the heat conduction within the pipe wall.

[0046] FIG. 6 illustrates an annealing apparatus 12 through which the OCTG pipe 1 is caused to perform a relative movement. The annealing apparatus 12 has an induction coil 11, and the OCTG pipe 1 is moved in the transport direction T through the induction coil 11. In part mutually different strength may be set through variation of the transportation speed in the transport direction T and/or by means of the energy density introduced into the OCTG pipe 1 by means of the induction coil 11.

[0047] Alternatively and/or additionally, multiple induction coils 11, 11a may be arranged and actuated separately, such that, for example, one coil 11, 11a is utilized in permanent operation and thus gives rise to a uniform introduction of heat in the OCTG pipe 1 being heat-treated/annealed in each case. A further coil 11a may then introduce additional heat into the pipe 1 intermittently, in particular in the region of the pipe body 2, and thus lead to a more intense annealing effect.

[0048] The foregoing description of some embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The specifically described embodiments explain the principles and practical applications to enable one ordinarily skilled in the art to utilize various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. Further, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as described by the appended claims.