Molecular dynamics study of surfactant-modified water-carbon dioxide systems

Alternating water/flooding is known to be very efficient for enhanced oil recovery, but is often economically infeasible for small sources. A similar effect can be achieved indirectly via injection of water-mixture with low molecular-weight emulsifiers with affinity for polar segments of residual hydrocarbons. To investigate the potential of this approach, we have performed molecular simulations of N-acetyl morpholine (NAM) and N-formyl morpholine (NFM) surfactants in liquid systems at K and Atm. The surfactants were modelled by means of the OPLSAA force field, with quantum mechanical calculations used to obtain the partial charges. Our simulations clearly showed the affinity of both NAM and NFM for the interface, providing extensive evidence of their interfacial activity. We also present an intuitive technique aiming to find and analyse intrinsic surfaces that define liquid-liquid interfaces by utilizing instantaneous and time averaged atomic configurations. This analysis allowed us to quantify the impact of NAM and NFM on the intrinsic surface structure of in liquid systems. Our results indicate that the instantaneous structure of intrinsic surface will be significantly roughened by the presence of NAM and NFM.