Investigating the impact of injection-water salinity and well strategies on water mobility and oil production in an oil-wet reservoir

Abstract

Waterflooding operation is one of the conventional and well-tested methods to improve oil recovery. However, in an oil-wet reservoir system, high water mobility is a primary concern resulting in lower oil production. This study, hence, aims to investigate the impact of injection water salinity changes on oil production and water mobility. With this, the variation of wettability and production of salt due to changing injection water salinity is also a part of this study. This study initiates with generating a three-dimensional, two-phase oil and water model. The reservoir is initially in the oil-wet stage. During the simulation, the relative permeability curves are adjusted to mimic the wettability alteration from oil-wet to water-wet. Initially, the impact of salinity on the oil recovery, water mobility, and salt production is studied through the sensitivity analysis between the low-saline and high-saline water injection. Later, a comparison of two injection strategies, including direct line and five-spot, is conducted to determine an effective injection technique for the comprehensive analysis of salinity changes on a waterflooding project. At last, the sensitivity analysis of different water salinity ranges of 0–35,000 ppm has been performed to compare the water salinity effects on water mobility, oil production, and salt production. It has been found through simulation that the oil recovery is improved significantly as the salinity of injected brine decreases below 5000 ppm. The oil recovery factor obtained while decreasing the salinity is as high as 72%. Moreover, the water cut is highly delayed as the salinity of water decreases. Furthermore, salt production is significantly lowered at the production well. Hence, reducing the salinity of injection water proved to be an effective strategy to recover more oil from an oil-wet reservoir.