Cost Optimization Study of Soak Period and Production Cycles of Cyclic Steam Injection in Lower Fars Heavy Oil LFHO Reservoir

Abstract

Abstract The cyclic steam stimulation (CSS) and injection process is a thermal recovery process consisting of three main stages: steam injection, steam soak and production of the heated oil. Before a stimulated well is put into production, a soak period is required to allow the injected steam to heat the oil around the wellbore and reduce its viscosity so that it will become more susceptible to flow. In actual operations, the soak period could vary from days to weeks, or even months. Prolonged soak period causes the well productivity to decline because of the continuous heat loss to the formation. On the other hand, insufficient soak period prevents effective transfer of the heat from the wet steam into the formation. For this reason, it is desirable to determine the optimal soak period that will maximize oil production and net profit during cyclic steam injection. The injection period at the beginning of the cycle, as well as its ensuing production period is also investigated to verify which stage in the CSS process is most influential in assuring higher recovery. In this study, a thermal, numerical reservoir oil simulator is utilized to evaluate the effect of varying the injection volume, soak period and production period with a view to improving crude oil recovery in Ratqa-North Kuwait Lower Fars Heavy Oil (LFHO) reservoir. Further economic studies are then pursued to determine the effectiveness of cyclic steam injection operations whilst maintaining a safe operational environment ensuring cap-rock integrity and also avoiding localized pockets of higher pressure and temperature (heaving). The key findings from this study was that the maximum injection period (60 days), minimum soak period (5 days) and minimum production period (90 days) are required for every cycle, in order to maximize recovery and optimize the cost.