Expandable Steel patch has a wide application in oil and gas wells. The patch restores the casing integrity but it poses inside diameter (ID) restrictions leading to difficulties in running completion equipment. This paper focuses on mechanical seal of perforations with full bore access and shares an overview of the general idea, well design, operational plan, successful field installation, and testing of the patch that provided full bore accessibility with a reliable seal of the perforations.

The technique was a preplanned approach where placement of a short section with bigger ID casing joints across possible perforated or damaged zones was included in the well program and implemented when drilling the well. After the well objectives had been achieved, the perforated zone was "sealed off" with a casing patch. The setting procedure of the selected casing patch technology was very different from that used with other expandable systems.

When running the 7″ liner string, the selected compatible liner hanger system and outside diameter (OD) of the liner wiper plugs covered both the 7-5/8″ and 7″ casing IDs. Also, cleanout tools, such as casing brush, scrapper, magnets and junk baskets, should cover the ID range. The selected patch's setting mechanisms is different, in which the steel is not pushed out with a fixed diameter metal expansion tool (cone), but is expanded using a pressure activated inflating and deflating packer, which will ensure the patch is pushed out (expanded) to seal effectively against the inside of the existing casing, irrespective of the precise casing internal diameter. This expandable steel patch allowed achieving the full bore access below the patch along with seals above and below the patch to avoid any future flow into the wellbore. Since the application was installed without performing a cement squeeze job before the patch, a significant time saving was also achieved. The idea of using the 7-5/8″ casing joints as part of the 7″ liner and setting the patch inside the bigger ID was successfully implemented; and integrity as well as full-bore access were ensured in the application.

This method and knowledge can benefit the oil and gas industry. The paper shares the entire experience obtained during designing, planning, and successfully installing a fit-for-purpose casing patch that brought value in terms of bore access and possibility of future interventions.

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