Mineral dissolution and fine migration effect on oil recovery factor by low-salinity water flooding in low-permeability sandstone reservoir

Abstract

The latest oil price decline simply increases the demand for enhanced oil recovery (EOR) and pushes research developers to keep improvements in oil recovery. The goal is always to recover as much oil as possible at the lowest possible cost. Low-salinity water flooding (LSWF) is an EOR method that operates at a lower cost than other EOR methods. The objective of this study was to test the ability of low salinity waterflooding to improve oil recovery from low permeability sandstone reservoirs. Four types of tests were conducted: imbibition, core flooding, zeta potential and scanning electron microscopy (SEM) tests. Two key factors were studied: salinity of the injected water and aging time. Their influence on the amount of oil recovery, stabilized injection pressure, pH, and permeability reduction was determined. The results showed that injected low brine concentration resulted in improving oil recovery. The oil recovery factor results during the second water flooding cycle (after aging for 24 h) showed more oil recovered during low water salinity injections. The zeta potential results showed that decreasing the salinity of injected water resulted in a decrease of the zeta potential value for both injection cycles, before and after aging for 24 h. Results also imply Low-salinity water flooding redistributes the flowing paths by releasing sand particles and some fine minerals causing the flow path to narrow. Thus, low salinity water flooding can create a new streamline (fluid flow diversion) and improve both displacement and sweep efficiency.