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

Abstract

This research provides an atomistic picture of the role of ions in modulating the microstructural features of an oil-contaminated calcite surface. This is of crucial importance for the rational design of ion-engineered waterflooding, a promising technique for enhancing oil recovery from carbonate reservoirs. Inspired by a conventional lab-scale procedure, an integrated series of molecular dynamics (MD) simulations were carried out to resolve the relative contribution of the major ionic constituent of natural brines (i.e., Na+, Cl–, Mg2+, Ca2+, and SO4 2–) when soaking an oil-bearing calcite surface in different electrolyte solutions of same salinity, namely, CaCl2, MgCl2, Na2SO4, MgSO4, and deionized water (DW). In all cases, we observed the gradual detachment of polar oil molecules (mimicked by decanoate) already paired to Na+ cations, covering the calcite substrate in such a way that carboxylate groups were in contact with the treating solution. The appearance of such a negatively charged interface in conjunction with the bare calcite/brine surface is a likely nanometric source for the disparity of surface characteristics of oil-bearing rocks reported in the literature. The MD results showed the affinity of divalent cations (Ca2+ or Mg2+) for pairing with negatively charged carboxylate functional groups, thereby facilitating desorption of decanoates. Having a compact solvation shell, Mg2+ was not as effective as Ca2+ cations; however, its performance was enhanced in the presence of sulfate anions. We further figured out the tendency of SO4 2– anions to shielding Na+ sites over the calcite surface, thus limiting the chance of readsorption of carboxylate compounds. Consistent with lab experiences, sulfate was found to assist the access of magnesium cations to the calcite surface as well. Altogether, the present results provide us with a molecular-level validation for the well-known multicomponent ion exchange mechanism proposed for the wettability alteration of carbonate rocks through enriching the divalent ionic content of the injection brine solution.

Study of the Adsorption Behavior of Surfactants on Carbonate Surface by Experiment and Molecular Dynamics Simulation

“…Besides, salinity would influence the surfactant-calcite carbonate interaction force. The heavy oil-calcium carbonate interfacial behavior was influenced by the CaCO 3 mineral surface chemistry and polar hydrocarbons residing charged ( Badizad et al, 2021 ). The surfactant adsorption onto the calcite surface was also influenced by the CaCO 3 mineral surface chemistry and polar hydrocarbons residing charge.…”

Salinity-Driven Structural and Viscosity Modulation of Confined Polar Oil Phases by Carbonated Brine Films: Novel Insights from Molecular Dynamics

“…The decane, BA molecules, Na + , and Cl – ions were modeled using the OPLS-AA force field . Recent studies have shown the compatibility of these force fields to reproduce the correct physical system. ,− The EPM2 model was utilized to describe the carbon dioxide molecules.…”

Salinity and pH effects on water–oil–calcite interfaces by using molecular dynamics

“…Particularly, in the case of calcium carbonate reservoirs, a key mechanism is the preferential adsorption of specific ions on the carbonate surface, i.e., MIE. 33,34 Moreover, some studies have indicated that the presence of divalent ions in seawater, such as sulphate anions (SO 4 2À ), and calcium (Ca 2+ ) and magnesium (Mg 2+ ) cations, can displace monovalent ions (mainly Na + cations) adsorbed on the carbonate surface, which increases wettability to water, improves crude oil release and facilitates good production. 34 Recently, the effectiveness of the SW in the EOR has been demonstrated in both laboratory and field studies.…”

“…33,34 Moreover, some studies have indicated that the presence of divalent ions in seawater, such as sulphate anions (SO 4 2À ), and calcium (Ca 2+ ) and magnesium (Mg 2+ ) cations, can displace monovalent ions (mainly Na + cations) adsorbed on the carbonate surface, which increases wettability to water, improves crude oil release and facilitates good production. 34 Recently, the effectiveness of the SW in the EOR has been demonstrated in both laboratory and field studies. 30,[35][36][37][38] For example, Zallaghi et al studied the synergy that occurs when SW and surfactants are injected into carbonate reservoirs.…”

“…[39][40][41][42][43][44][45][46] For example, using in silico methods, researchers have obtained insights into the interactions between aqueous ions, minerals, and crude oil models, information that has led to an understanding of the role of SW in altering mineral wettability. 34,39,40 Badizad et al provided an atomistic insight into the role of ions (100 000-300 000 ppm) in modulating the microstructural features of an oil-wet calcite surface. 34 Specifically, the authors concluded that Ca 2+ and Mg 2+ tend to coordinate negative carboxylates in the water bulk, facilitating the detachment of carboxylic acids from the calcite surface; also, SO 4…”