|
|
The HETS expandable External Casing Patch (Tie-Back) connection is an effective and long term method of connecting new casing to a casing stub downhole, and which provides a hydraulic and gas-tight connection capable of withstanding hundreds of tons of cyclic loading at well temperature, whilst maintaining the integrity and full I.D. of the original casing.
The HETS External Casing Patch connection principle is based on the elastic / plastic expansion and subsequent relaxation of metals. The HETS overshot is run, on space-out casing, over the casing stub in the well. The casing stub is then hydraulically plastically expanded (permanently deformed) by the HETS tool . The tool is run on drill pipe and permanently moulds (conforms) the casing stub to the internally grooved profile of the HETS overshot using high hydraulic pressure. During this operation, the HETS overshot undergoes elastic expansion only, and therefore when the hydraulic pressure is released from inside the casing, the HETS overshot relaxes back to its original dimensions. This shrinkage is resisted by the permanently deformed casing (e.g. expanded by 5 - 9%) resulting in significant interfacial pressure between the casing and the overshot. This interference fit achieved across the grooved section provides both the metal-to-metal seal and the resistance to axial loading of the connection.
Features
Applications
Q: Can the connection be made under tension?
A: Yes - using a grapple and bowl assembly, the actual expansion can happen with the casing in tension
13/03/2006
