Impact of the injected water salinity on oil recovery from sandstone formations: Application in an Egyptian oil reservoir

Abstract

Abstract In the last decade, there has been an increasing interest in understanding the effects of changing injected water salinity on the performance of oil reservoirs. This paper aims to investigate the effects of injected water salinity on oil recovery of an Egyptian oil reservoir (Bahariya formation). An experimental work program has been performed using 25 core plugs and 5 different water salinities to study the effects of changing water salinity during both secondary and tertiary stages of waterflooding. The objectives of the experimental work were to (1) investigate the effects of the low water salinity on oil recovery and (2) identify the optimum water salinity and the main reservoir parameters for application of low salinity waterflooding project (LSWF) in Bahariya formation. The results revealed that there is an optimum salinity for waterflooding in the secondary flooding stage. However, for the tertiary flooding stage, the results showed that the controlling factor is not decreasing the salinity, but rather changing the salinity (e.g. either increasing or decreasing). It was also clear that applying the optimum salinity in the secondary recovery stage is more effective than applying it in the tertiary recovery stage. Furthermore, the results showed that the positive impact of LSWF may be expected in reservoirs with high amount of kaolinite, high values of CEC, and low amounts of plagioclase feldspar. This study is an original contribution to develop guidelines for designing optimum salinity waterflooding projects in sandstone reservoirs.