Abstract
Long, expandable liners offer practical solution for restoring well integrity in small-diameter wells with severe corrosion problems. Previous options for repairing these wells required running a tubing string to the producing interval, with a restrictive ID that limited production rates. New expandable liner technology, which has been proven in relining horizontal well sections exceeding 4500 ft, can be installed over the full length of vertical wells with small-diameter casing, sealing damaged areas with minimal ID reduction. The system includes packers and nipples that enable completion without a tubing string. In addition to extensive experience in North America, the system has been used successfully in Saudi Arabia to install a 315-ft casing patch to seal a corroded section in a demonstration well.
Many producing oil and gas wells in Saudi Arabia and throughout the Middle East were completed with cost-effective 4.5 in or 5.5 in production casing. Due to the casing's small diameter, options to repair corrosion or other integrity issues are limited. Running a production tubing string with completion packers can be costly, and the restricted ID can limit production rates. Expandable liner technology, originally developed to install casing patches of a few hundred feet, has been enhanced to enable installation of continuous expanded liners that can extend beyond 5,000 ft.
The liners are comprised of high-performing expandable alloy rated for high-H2S service and incorporate expandable threaded connectors. The liner is run to the desired depth and is expanded from the bottom using a downhole hydraulic jacking system to initiate the expansion and the rig's draw works to finish it. In typical 4.5-in casing, the resulting internal diameter is 3.4 in. The liner system includes metal-to-metal seals at top and bottom and can be fitted with production packers and nipples for gas lift valves, as required.
The expandable liner system has successfully addressed integrity problems on more than 100 wells. Recent applications in horizontal wells demonstrated the efficient installation and consistent expansion of the liner. Horizontal liners in excess of 4000 ft were expanded in an average of 29 hours and maintained integrity during hydraulic fracturing. The system also was used in Saudi Arabia to repair a corroded 300-ft section of 4.5-in casing in a producing well, with good results.
