Oil Recovery by Low Salinity Brine Injection: Laboratory Results on Outcrop and Reservoir Cores

Abstract

Abstract Over the last 10 years, the emerging EOR process by injection of low salinity water has been investigated through numerous laboratories and some field tests. Extensive research programs have been launched by different teams, aiming at better understanding the involved mechanisms (clay release, pH increase, cation exchange). One of the main issues is to explain the observed dispersion in additional oil recoveries. In this study, we integrate new experimental observations to the literature to carry out a mechanism analysis of recovery by low salinity injection. These new results were obtained on outcrop sandstones with 9-10 % clay content (Cissokho 2009) and on reservoir cores with reservoir oil. Very positive results to dilute brine injection on the outcrop rock / crude oil of field A system have been observed either in tertiary mode or secondary mode. Corefloods on the same outcrop rock/ crude oil system show that the benefits of low salinity brine injection may vary against the flood temperature. Corefloods in pseudo-reservoir conditions using reservoir cores and the same crude oil of field A showed no response to injection of low salinity brine. Corefloods using reservoir cores and oils from three different fields did not show any positive response to dilute brine injection. In this paper, we analyze the different theories proposed in the literature and present experimental counter-examples for most of them, particularly related to the presence of kaolinite, divalent ions in injected brine, or the effect of temperature. We show that low salinity water injection as an EOR method appears very sensitive to a combination of several parameters.