Effects of Injection Rate of Low Salinity Brine on Oil Recovery Mechanisms and Relative Permeability Curves

Low Salinity Brine (LSB) injection has been widely studied and several oil recovery mechanisms are proposed. Implementation of LSB injection does not yield only benefit from physical displacement as obtained from conventional waterflooding, it also provides displacement from chemical process. However, both displacement mechanisms might not occur at the same time. Physical displacement occurs immediately once water is injected into formation but chemical displacement might require time to increase retention of potential ions onto rock surface. Injection rate of LSB is therefore, considered as a key parameter to maximize oil recovery from this technique. From the study, moderate injection rate yields benefit from both displacements mechanisms and as a consequence, the highest oil recovery factor is obtained. Small injection rate favors only chemical displacement mechanism, whereas part of oil is remained untouched in case of high injection rate. Unsteady state relative permeability curves are constructed and they are good evidences to explain oil recovery mechanisms from different injection rates. Great reduction of relative permeability to water at residual oil saturation suggests that chemical process is favorable at lower injection rates.