Abstract
Due to the need to enhance petroleum and gas recovery, scientists and engineers constantly seek various ways of enhancing recovery especially during water flooding process. Salinity of the water injected and type of core material studied from the formation are key factors that can enormously impact on the oil recovery. The knowledge of the impact of salinity on oil recovery during water flooding using core samples containing clay, unfortunately, has been limited. This paper investigated the impact of salinity on oil recovery carried out using two core samples obtained from shale rocks. The core sample labelled A was from Kogi state and core B was from Rivers state. Initially both core samples were dried in an oven at 88°C to cause natural fractures and connect the pore spaces then saturated with brine of 20g/l salinity and light crude oil of viscosity 3.35cp to simulate reservoir conditions within the core samples. The porosity of the samples was determined by liquid saturating method and the effective permeability was calculated using Darcy’s law. Core flooding tests were conducted by injecting brine and varying the salinity levels at 10g/l to 50g/l to displace 20 ml of light crude oil originally saturated in each core sample. The results and analysis of the tests showed that the core sample B recovered more oil than sample A. The recovery factor efficiency of core A was 24%, 31.5%, 51%, 53% and 53.5% and the core sample B was 26%, 42%, 50.8%, 52.1%, 55%. The oil recoveries at breakthrough increased significantly with increasing salinity. The difference in oil recoveries for both core samples was observed at 30g/l of brine salinity where core B recovered 8.8% higher than core A. At 50g/l brine salinity, the oil recovery efficiency did not change for both core samples while changing the concentration of brine relative to the initial brine used. The findings of this study and the data retrieved shows the improvement of oil recovery factor increases as brine salinity increases which can be attributed to interfacial tension reduction and viscosity alteration.

Key words: Water flooding, Salinity, Oil recovery, Brine, Water flooding, Core samples, EOR.