Optimization Experience on the Use of Carbon Steel Tubing for Sweet Corrosive Gas Field

Abstract

CRA 13%Cr has been used at all Mahakam swamp and offshore gas wells since 1990's for oil country tubular goods (OCTG) particularly for production tubing, due to its excellent CO2 corrosion resistance. By mid of 2000's, when depletion observed in one reservoir level, the new production started from different level, thus reduce the wells design life and increase the completion job frequency. To avoid completion delay due to tubing material delivery, CLAS 3%Cr and Carbon Steel (C-steel) tubing were proposed. By late 2010's, the study was done to develop materials selection guidelines to provide necessary information allowing early selection of the most appropriate and cost effective Steel for lower well completion. And finally, since 2015, C-steel tubing has been applied to all entire tubing (lower and upper completion a few hundred meter below safety valve) on sweet corrosive gas well through systematic corrosion and erosion assessment, which has been verified as well by tubing wall measurement logging. This paper summarizes the outcome of several studies has been done, and demonstrate the optimization on the use of C-steel tubing instead of higher grade material, as part of corrosion management strategy to synchronize fit for service and economical objective.