Interaction study of montmorillonite-crude oil-brine: Molecular-level implications on enhanced oil recovery during low saline water flooding from hydrocarbon reservoirs

Detailed molecular level insights of the interaction between the reservoir rock-crude oil-brine are very crucial for designing effective injection water during low saline water flooding for optimum oil recovery. Present work is an attempt to study the interaction phenomenon that takes place between different reservoirs components considering clay, two dead crude oils (C1 and C2), and different concentrations of brine (2000-8000 ppm). The clay used in this study is montmorillonite with a stoichiometric composition (Na0.63Ca0.26K0.1) (Al2.66Ti0.44Fe0.60Mg0.61) (Si6.538Al1.46) (OH)(4). Crude oil C1 is lighter having 3 wt% asphaltene dominating with 3-5 fused aromatic ring (FAR) structures while C2 is heavier than C1 containing 7.5 wt% asphaltenes with a significant presence of 5-7 FAR. Experimentation and detailed analysis of the dry (Mt) and oil-treated montmorillonite (MtC1, and MtC2) connote that the polar oil components particularly, asphaltenes are adsorbed onto the interlayer surfaces of montmorillonite. Spectroscopic results of oil treated Mt and saline water reveal that low saline water (2000 ppm) of Na+ and Ca++ ions are equally capable of removing 3-5 ring size FAR of polycyclic aromatic hydrocarbon (PAH) components from the montmorillonite interlayer surfaces. Thus, the present study attests to the fact that the type of cation present in their interlayer surface of montmorillonite, and the ring size of PAH in asphaltenes influence the interaction phenomenon where molecular level insights between oil treated montmorillonite and saline water are valuable for designing effective injection fluids for EOR.