Faced with water influx from an abandoned side track lateral, Petroleum Development Oman (PDO) weighed the alternatives. The simple solution of setting a bridge plug in the lateral and dumping a load of cement on top of it was impractical. First the well was deviated 92° in the section where the lateral junction occurred, and although the lateral was only 13 ft (4 m) long, the casing was in bad shape. Furthermore the hydraulic integrity of the junction itself was questionable.
The company's engineers had determined the requirement to implement a non-cemented isolation capable of withstanding 5,000 psi differential pressure. The only solution seemed to be setting several hundred meters of scab liner in the main bore to bridge over and isolate the junction.
But a scab liner posed additional problems. The company was interested in re-installing the original completion in the main bore which was cased with 7-in. 23 lb/ft casing. Could the original completion pass through the scab liner, they asked?
Weatherford engineers suggested an alternative solution. They proposed using a short section of MetalSkin expandable cased-hole liner to bridge across the lateral junction (Figure 1). After expansion, the liner's inside diameter (ID) would leave plenty of clearance to pass the completion string. And it would provide a positive, reliable seal that would hold the required differential pressure.
A unique feature of the system is the use of a roller-type expansion tool that imposes a compliant expansion profile on the liner that conforms itself to the ID of the well bore in which it is set. This means that the MetalSkin liner can compensate for any small irregularities or ovality in the casing profile and create a high-integrity seal.
The expandable liner was successfully set between 4,952 ft and 4,997 ft (1,510 m and 1,523 m) across the lateral junction and was pressure tested to 1,000 psi. The compliant expansion feature enabled the liner to compensate for the poor condition of the casing around the milled window, and because the post-expansion steel skin is strong but thin, the final ID of the repaired section provided enough clearance to allow reinstallation of the original completion string.
Summarizing the value of the solution to the operator:
• The MetalSkin solid expandable casing liner eliminated the need to run a costly scab liner;
• It eliminated the need to change the completion design;
• It provided a non-cemented solution for high-pressure isolation with maximum throughbore; and
• It solved the problem of unwanted water influx in spite of poor casing conditions and junction integrity, while allowing future re-entry for workover.
No specialized rig equipment was required to run, expand and test the liner. The well was returned to production following the repair job and is delivering good results. No recurring water influx has been detected from the repaired section.

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