Development of a Hydraulically Expanded Metal Internal Casing Patch
Authors: Bybee Karen 
Published: February 2015

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 94056, "Development of a Hydraulically Expanded Metal Internal Casing Patch," by F. Louden, SPE, Read Well Services Ltd.; E. Mathiassen, SPE, Statoil ASA; P. Hazel, Read Well Services Ltd.; F. Skjerping, Statoil ASA; A. Gorrara, SPE, Read Well Services Ltd.; and K. Boe, SPE, Statoil ASA, prepared for the 2005 SPE/ICoTA Coiled Tubing Conference and Exhibition, The Woodlands, Texas, 12-13 April.
The full-length paper details the technical development and implementation of a coiled-tubing (CT) -deployed, expandable internal metal casing patch. The technology was developed to introduce an internal-casing-patch system for deployment in 7-in. tubing. This patch was designed to extend completion life and delay a full workover operation. The compliant patch provides a substantive localized tubing repair (e.g., water shutoff, leak repair, and corroded-pipe patch) with minimal inside-diameter (ID) restriction to optimize access for future well interventions and minimize the restriction to oil production (or water injection).
Introduction
During the 18-month research and development project, the project team designed and built a hydraulically expandable steel patch, the running tool to deploy and expand the patch, related downhole and surface hydraulics, and the CT interface. The running tool was designed to be deployable on CT or drillpipe, and the patch was designed to provide a metal-to-metal seal (with an optional elastomeric seal for badly corroded pipe) that also would improve casing burst and collapse ratings.
System Components
Downhole Deployment and Expansion Tool. The tool is a high-pressure hydraulically actuated dual-packer expansion device. After the two rubber seals (separated by extension mandrels configurable from 10 to 46 ft long) are actuated, high-pressure fluid is pumped between the seals. The pressure is increased and expands the patch first elastically then plastically with approximately 5,000 psi hydraulic pressure. The pressure on the seals is controlled to ensure that the seal is maintained until full contact with the outer tubing/casing is achieved. As the pressure continues to increase, the outer tubing is elastically strained until the predetermined and preset final swage pressure is achieved. The pressure then is bled off, and the seals are retracted by use of a 1,500-psi retract cycle. The seal design includes a polymer sealing element and antiextrusion backup steel fingers and is pressure rated for 25,000-psi operation. Fig. 1 shows the tool deploying an unexpanded patch across perforations and the resultant expanded patch.
Downhole Hydraulics System. A prerequisite of the project was to actuate the system and not expose the CT to pressures greater than 4,000 psi. To achieve the final 10,000-to 17,000-psi swage pressure downhole, a downhole pressure intensifier was developed and incorporated into the downhole hydraulics system, which also includes other significant components. The tool is fitted with a contingency shear-release subassembly located at the bottom of the hydraulics section and below the CT bottomhole-assembly (BHA) adapter. This is designed to provide an internal and external fishing profile to facilitate fishing should the tool become stuck in the well.