Development of a Hydraulically Expanded Metal Internal Casing Patch

Abstract

Abstract This paper details the technical development & implementation of a Coiled Tubing (CT) deployed, expandable internal metal casing patch. The driver for the development of the technology was to introduce an internal casing patch system for deployment in 7" tubing, designed to extend the completion life and delay a full workover operation. The compliant patch would provide a substantive localised tubing repair (e.g. water shut-off, leak repair, patch corroded pipe) with minimal internal diameter restriction to optimise access for future well interventions, and hence minimise the restriction to oil production (or water injection). Introduction This paper reviews the technical challenges during the 18-month R&D project and details the final solutions. The project team designed and built a hydraulically expandable steel patch, the running tool to deploy & expand the patch, the related downhole & surface hydraulics and the coiled tubing interface. The running tool was designed to be deployable on CT or drill-pipe and the patch designed to provide a metal-tometal seal (with an optional elastomeric seal for badly corroded pipe), that would also improve burst and collapse casing rating. The paper will describe in detail the operational planning, pre-job testing and final implementation of the first commercial CT-deployed hydraulically expanded patch. It will also briefly review the components of the system including - the downhole expansion tool & associated high pressure seals / hydraulics (including 7:1 pressure intensifier), the expandable patch, the surface hydraulic system, the coiled tubing interface and the surface & downhole data recording equipment. Components of the system The HETS system is made up of four main componentsDownhole deployment & expansion toolDownhole hydraulics system & data moduleExpandable patchSurface hydraulic & recording system The outline design and function of each component will be reviewed to provide a basic understanding of the overall system operation. (Fig 1a) Downhole deployment & expansion tool. The tool is a highpressure, hydraulically activated ‘dual packer’ expansion device. After the two rubber seals are activated (they are separated by extension mandrels configurable from 3m to 14m long, high pressure fluid is pumped between the seals, the pressure increased and first elastically, then plastically expands the patch with the hydraulic pressure (approx 5,000psi). The pressure on the seals is controlled to ensure 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 & pre-set final swage pressure is achieved (typical range 13,000–17,000psi). The applied pressure is then bled off and the seals are retracted via a 1,500psi retract cycle. The seal design incorporates a polymer-sealing element, together with anti-extrusion backup steel fingers and is pressure rated for 25,000psi operation.