Modelling of Carbonate Rock Wettability Based on Surface Charge and Calcite Dissolution

Understanding the Effects of Mineral Impurities, Brine Ionic Composition and CO2 on Rock–Brine–Oil Electrokinetic Behavior Using a High-Salinity Surface Complexation Model

“…We considered calcium (>Ca) and carbonate (>CO 3 ) as the two lattice ions at the calcite–water interface, and based on Stipp, the study assumed a fractional charge of 0.25 for the calcite surface (>Ca +0.25 , >CO 3 –0.25 ). Previous studies ,,, used the same values for the calcite surface. In contact with the aqueous solution, these calcite surfaces get hydrated, forming new complexes: >CaOH –0.75 and >CO 3 H +0.75 .…”

“…). Previous studies 9,23,25,43 used the same values for the calcite surface. In contact with the aqueous solution, these calcite surfaces get hydrated, forming new complexes: >CaOH −0.75 and >CO 3 H +0.75 .…”

“…21,32 This means that the potential at the b-plane, as determined by PHREEQC, is equivalent to the ζ-potential. 9,21,22,32 Therefore, we compared our model's computed b-plane potential to the literature ζ-potential data sets. S1.…”

“…9 These interactions lead to the release of adsorbed oil from the rock surface, shifting the reservoir toward water-wet conditions. 9 Austad and co-workers 10−12 developed the concept of smart water and detailed the importance and mechanism associated with potential-determining ions (PDIs), including Ca 2+ , Mg 2+ , and SO 4 2− in altering chalk rock wettability for improved oil recovery. Various other researchers extended and observed a similar effect of PDIs on wettability alteration with limestone rocks, 13,14 dolomites, 15 and in anhydrite 11 rock formations.…”

“…LSW refers to brine with low salt concentration (typically below 5000 ppm), which is injected into the reservoir for better oil recovery . Smart water, on the other hand, refers to the use of brine with specific ionic compositions and salinity tailored at triggering a particular rock wettability state. , It is suggested that the injection of LSW or smart water into the reservoir disturbs the initial reservoir equilibrium, and for the reservoir to retain its equilibrium state, geochemical reactions occur between the aqueous species and the oil/rock surfaces . These interactions lead to the release of adsorbed oil from the rock surface, shifting the reservoir toward water-wet conditions .…”