Depleted Gas Zone Isolation in Cemented Monobore via Real-Time Coiled Tubing Expandable Steel Patch

Abstract

An operation in Malaysia successfully implemented coiled tubing (CT) expandable steel patches to isolate upper depleted zones so that lower gas zones could be produced. This serves to prove the technique as a method that can be used in top-down gas production isolate & perforate strategy. A bottom-up isolate & perforate gas production strategy has always been a practice in a cemented monobore with multi-zonal completions. This simple design has the benefit of enabling simple well intervention operations through the well’s production life in the wake of reserve recoveries. Typically, "plug and perf" is used to continue production from the upper zones with undeveloped/ behind casing reserves when the lower zones in the well are depleted to economic limit for them to be isolated. However, some cases require producing from top-to-bottom, which requires isolation of upper zones and perforate the lower zones. Real-time coiled tubing expandable steel patches were proposed as a solution for top-to-bottom production in a well in Malaysia, 5-½" expandable steel patches were installed with the greatest number of overlaps. The evaluation process prior to installation started with a well information review once the subsurface objective was determined. This thorough analysis identified the new zone to replace the existing depleted zone. Next, a comprehensive study assessed the isolation method, the appropriate conveyance, and the method to be used to validate the isolation integrity. The perforation strategy was then formulated to pass through the validated isolation section. Following the operation, lessons learned were collected and discussed. The method, results and lessons learned from the application of a real-time coiled tubing expandable steel patch represent a resource for applying the method to future wells with top-to-bottom production.