Achieving Zonal Isolation Objectives in Carbon Dioxide Rich Gas Production Environment in South East Asia

Abstract

Abstract Constructing wells in reservoirs with high concentrations of carbon dioxide (CO2) is a challenge in itself. In South East Asia region drilling campaign in a high-CO2 reservoir was made even more difficult because of high well deviation, long production sections, a narrow drilling window, and loss of circulation. Prior attempts to develop the field established that this reservoir would not be easily exploited. One complicating factor was that the reservoir has multiple stacked layers of sand up to 8 zones in each well, These zones have different pressure regimes that are spread out in the reservoir section of average 3,000 meters per well. Effective mud removal is essential to achieve zonal isolation in these wells because mud left behind the cement will likely result in communication between the zones. In order to realize the long-term production plans for these offshore wells, the operator needed a fit-for-purpose cementing solution. The operator was able to successfully overcome the aforementioned challenges and successfully cement seven wells using a system that incorporate blast furnace slag (BFS). The wells were drilled with a jackup rig in a water depth of 90 m [274 ft]. A cement evaluation log and the absence of sustained casing pressure confirm that there have been no zonal isolation concerns since the first well started producing in November 2013. The BFS system has proven to be cost effective and has the added advantage of being compatible with the existing cementing equipment without any special modifications.