Atomistic Insight into the Behavior of Ions at an Oil-Bearing Hydrated Calcite Surface: Implication to Ion-Engineered Waterflooding

This research provides an atomistic picture of the role ions in modulating microstructural features oil-contaminated calcite surface. is crucial importance for rational design ion-engineered waterflooding, a promising technique enhancing oil recovery from carbonate reservoirs. Inspired by conventional lab-scale procedure, integrated series molecular dynamics (MD) simulations were carried out to resolve relative contribution major ionic constituent natural brines (i.e., Na+, Cl–, Mg2+, Ca2+, and SO42–) when soaking oil-bearing surface different electrolyte solutions same salinity, namely, CaCl2, MgCl2, Na2SO4, MgSO4, deionized water (DW). In all cases, we observed gradual detachment polar molecules (mimicked decanoate) already paired Na+ cations, covering substrate such way that carboxylate groups contact with treating solution. The appearance negatively charged interface conjunction bare calcite/brine likely nanometric source disparity characteristics rocks reported literature. MD results showed affinity divalent cations (Ca2+ or Mg2+) pairing functional groups, thereby facilitating desorption decanoates. Having compact solvation shell, Mg2+ was not as effective Ca2+ cations; however, its performance enhanced presence sulfate anions. We further figured tendency SO42– anions shielding sites over surface, thus limiting chance readsorption compounds. Consistent lab experiences, found assist access magnesium well. Altogether, present provide us molecular-level validation well-known multicomponent ion exchange mechanism proposed wettability alteration through enriching content injection brine