Improvement of Water Displacement Efficiency in Sandstone Reservoirs Using Buffered Sodium Silicate

Abstract

This work addresses the influence of buffered sodium silicate, (SiO2)3.35Na2O, on water-oil displacement efficiency in quartz media using static and flooding experiments. IFT measurements reveal that sodium silicate-oil interfacial tension is a function of the solution pH. At a given pH, sodium silicate has considerably lower IFT compared to NaOH, which is a strong alkali. Modified quartz chunks with silicate solution show a lower water contact angle in oil compared to unmodified ones, which may be explained by quartz surface charge modification due to alkalinity of sodium silicate as well as increased number of hydroxyl groups on the mineral surface due to silicate chemi-adsorption. Spontaneous imbibition tests at micro and macro-scale using glass micro-model and sandstone cores show that sodium silicate effectively enhances water imbibition rate and final oil recovery factor. This is more evident in the case of asphaltenic oils, first because sodium silicate reduction of IFT is considerably higher in presence of asphaltene (IFT<1 dyne/cm). On the other hand, sodium silicate diminishes the rigid film of asphaltene, which resists water-flooding. Sodium silicate also affects the water-oil relative permeability curves by shifting their cross section to higher water saturations, indicating wettability alteration to more hydrophilic.