Patent EA-000543-B1 (EA)
Title: Method for expanding a steel tubing and well with such a tubing
Inventor: DONNELLY MARTIN
IPC: B21D39/20
Filed: 1997-06-30
Abstract: 1. A method of expanding a steel tubing (4) which is made of a formable steel grade, the method comprising the step of moving an expansion mandrel (5) having a tapering expansion section (6) through the tubing (4) thereby plastically expanding the tubing, characterized in that an at least partly solid tubing (4) is expanded which is made of a formable steel grade which is subject to strain hardening without incurring any necking and ductile fracturing as a result of the expansion process and that the tapering expansion section (6) of the expansion mandrel (5) has a tapering ceramic outer surface. 2. The method of Claim 1, wherein the tubing (4) is made of a formable steel grade having a yield strength-tensile strength ratio which is lower than 0.8 and yield strength of at least 275 MPa. 3. The method of Claim 1 or 2, wherein the tubing (4) is made of a steel having a yield strength-tensile strength ratio which is between 0.6 and 0.7. 4. The method of Claim 1, 2 or 3, wherein the tubing (4) is made of a dual phase (DP) high-strength low alloy (HSLA) steel. 5. The method of Claim 4, wherein the tubing (4) is made of Sollac grade DP55 or DP60 having a tensile strength of at least 550 MPa or Nippon grade SAFH 540 D or SAFH 590 D. 6. The method of Claim 1, 2 or 3 wherein the tubing (4) is made of a formable high-strength steel grade which is selected from the following group of steel grades: - an ASTM A106 high-strength low alloy (HSLA) seamless pipe; - an ASTM A312 austenitic stainless steel pipe, grade TP 304 L; - an ASTM A312 austenitic stainless steel pipe, grade TP 316 L; and - a high-retained austenite high-strength hot rolled steel which is known as TRIP steel. 7. The method of any preceding Claim, wherein the tubing is expanded such that the external diameter of the expanded tubing is at least 20% larger than the external diameter of the unexpanded tubing (4) and wherein the strain hardening exponent n of the formable steel of the tubing (4) is at least 0.16. 8. The method of any preceding Claim, wherein the expansion mandrel (5) comprises a tapering expansion section (6) which has a smooth ceramic outer surface which is oriented at an acute angle A which is between 5 degree  and 45 degree  with respect to a longitudinal axis of the mandrel (5) and which induces the tubing (4) to expand without inducing any galling of the tubing and such that the average roughness of the inner surface of the tubing (4) decreases as a result of the expansion process. 9. The method of Claim 8, wherein the ceramic outer surface of the tapering expansion section (6) is made of zirconium oxide and is oriented at an acute angle A which is between 15 degree  and 30 degree  with respect to a longitudinal axis of the mandrel (5). 10. The method of any preceding Claim, wherein the tubing (4) is expanded by pumping the expansion mandrel (5) through the tubing (4). 11. The method of Claim 7 and 10, wherein the expansion mandrel (5) comprises a sealing section (7) which is located at such a distance from the expansion section (6) that when the expansion mandrel (5) is pumped through the tubing (4) the sealing section (7) engages a plastically expanded part of the tubing. 12. The method of Claim 10 or 11, wherein the tubing (4) is expanded inside an underground borehole and the expansion mandrel (5) contains a vent line (8) for venting any fluids that are present in the tubing (4) ahead of the expansion mandrel (5) to the surface. 13. The method of Claim 10 or 11, wherein the tubing (4) is expanded inside an underground borehole such that the outer diameter (D2) of the expanded tubing (4) is slightly smaller than the internal diameter of the borehole or of any casing (2) that is present in the borehole and any fluids that are present in the borehole and tubing (4) ahead of the expansion mandrel are vented to surface via the annular space that remains open around the tubing (4) after the expansion process. 14. The method of any preceding Claim, wherein the tubing (4) is lowered into an underground borehole after reeling the tubing from a reeling drum. 15. A well provided with a tubing (4) which is expanded using the method of any preceding Claim, wherein the tubing (4) serves as a production tubing through which hydrocarbon fluid is transported to the surface and a reelable service and/or kill line passes through at least a substantial part of the length of the interior of the tubing (4), through which line fluid can be pumped towards the bottom of the borehole while hydrocarbon fluid is produced via the surrounding production tubing (4). 16. A well provided with a tubing (4), which is expanded using the method according to any one of Claims 1-12, wherein the tubing is expanded against the inner surface of a casing (2) which is present in the borehole.