Abstract
In this study, we propose to quantify a control of water chemistry on water-rock interactions and wettability alteration during Lo-Sal water-flooding of sandstone cores containing heavy oil. We intended to identify the dominant process of wettability alteration through considering all possible water-rock interaction mechanisms simultaneously. Water chemistry partially determines the dominant wettability alteration. This includes salinity, type of ions, and possibly pH.
The effect of the potential determining ion towards sandstone ‘calcium ion’ is presented in this work. The ultimate oil recovery for the core saturated in normal Ca2+ concentration at higher temperature was higher than the core saturated with double Ca2+ at the same temperature. The divalent cation (Ca2+) concentration was then doubled in the aging water, resulting in a lower oil recovery. The thermal technique seems to be related to the chemistry of the water, meaning that the injected hot water must be tuned to the proper chemical composition. Desorption of Ca2+ is associated with pH jump and thereby increased microscopic sweep efficiency, and it seems to have a large impact on LS water EOR heavy oil.
