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

Abstract

ζ-Potential is applied in many subsurface processes including in the petroleum industry, deep saline aquifers, and geothermal fields to understand oil recovery, hydrogen, and CO2 storage. Typical subsurface formations contain high-salinity brine with multicomponent ionic species and varying mineral impurities. However, predicted ζ-potential models make use of surface complexation models (SCMs) compatible with low-salinity brine and/or single-salt brine and single mineral composition. In this study, a basic Stern model (BSM) is proposed to compute the rock–brine–oil ζ-potential at high salinity conditions, varying brine ionic composition, complex mineralogy, and CO2. The effects of impurities, modeled through dissolution reactions, and their influence on the ζ-potential were included in the developed model. The developed BSM was observed to capture the literature-reported ζ-potential measurements with an ionic strength as high as 5.4 M, suggesting that our model can be applied to other subsurface conditions, such as geothermal fields and deep saline aquifers, where the reservoir usually contains high-salinity brine. The simulation results showed that increasing the SO4 2–-ion concentration can decrease the smart water oil recovery in carbonate formation but improve the oil recovery in the quartz reservoir. Meanwhile, high Mg2+-ion concentration can reduce the smart water oil recovery in both carbonate and quartz reservoirs. The study further showed that the presence of impurities in the carbonate rock can make the carbonate reservoir more water-wet and increase the smart water oil recovery. However, the presence of impurities in the sandstone reservoir can render the sandstone reservoir oil-wet and decrease the smart water oil recovery. Our study demonstrated that high pCO2 can make both the carbonate and sandstone reservoirs more water-wet and improve the smart water oil recovery. In general, the results produced from this study suggest that the SCM should incorporate the mineral impurities into geochemical reactions so that true reflection of the surface chemistry can be captured by the model.

The Role of the Mineralogical Composition on Wettability via Flotation Test and Surface Complexation Modeling (SCM)

“…In addition, the possible oil-brine interactions and their reaction constants have also been reported in literature [10,13,14]. Numerous developments have been made in recent years by several researchers to exploit these existing SCM data from literature to elucidate the mechanism during the experiment [22]. For example, zeta potential measurements have successfully been modeled via SCM [22,23].…”

“…Numerous developments have been made in recent years by several researchers to exploit these existing SCM data from literature to elucidate the mechanism during the experiment [22]. For example, zeta potential measurements have successfully been modeled via SCM [22,23]. In addition, research has shown that the SCM technique is capable of modeling polymer interactions such as precipitation reactions at high surface coverage [24].…”