Investigation of the Molecular Basis of Chemical Enhanced Oil Recovery Fluid-Fluid Interactions Through NMR Spectroscopy

摘要

As the world depletes its supply of easily accessible crude oil, improved oil recovery methods become more valuable. In general, decreasing the injection brine salinity increases the amount of oil recovered. There are various techniques, especially in chemical enhanced oil recovery, which elicit beneficial recovery responses, for example smartwater flooding, use of surfactants, polymers, and various combinations. There is much debate as to the mechanisms through which low-salinity flooding is so effective, though conclusions lead to wettability alteration. Much effort has been invested into rock-fluid interactions, with little attention directed toward fluid-fluid mechanisms. Previous work in this group has shown that fluid-fluid interactions can improve recovery without any adjustment to the rock-fluid relationship. These fluid-fluid interactions were caused in some cases by adjustment to acid content, and explored the benefits of this through visco-elasticity measurements. This work with naphthenic acids -inherent to crude oils- was continued, but specific acids were analyzed with both NMR and interfacial visco-elasticity. Specific acids were shown to have different effects on the interface, and the strength of emulsions formed, both of which will affect oil recovered.;In addition to species inherent to the crude, this work also investigates surfactants, generally used to achieve ultra-low interfacial tension values and induce emulsification. These amphiphilic molecules are most effective when paired with a polymer blend, and they are highly affected by water hardness and temperature; as such care must be taken when selecting injection water and surfactant pairings. A formulation was designed for an offshore, carbonate, heavy oil reservoir, where seawater was used as the carrying fluid. The forced imbibition results turned out promising in terms of oil recovery, reaching almost 90%. The Nuclear Magnetic Resonance (NMR) spectroscopy protocol, developed in collaboration with a previous student, was used to estimate Critical Micelle Concentration (CMC) and individual component's concentration for coreflooding effluents and static adsorption estimation. This protocol was tested at higher concentrations, in concert with dynamic light scattering and microscope techniques, to detect second order phase transitions.