Impact of water chemistry on fluid-fluid interfacial behavior: Implications in aqueous-based EOR

The rheological properties of water-crude oil interfaces are of prime importance in many applications in petroleum industry. Rigid (elastic) water-crude oil interfaces provide mechanical strength that controls the interface break up. Consequently, elastic interfaces will influence processes such as droplets coalescence and pinch-off, which are in turn controlled by interface rupture, among other mechanisms. Coalescence controls emulsion stability while pinch-off impacts snap-off in flow through constrictions. The connection to recovery processes is apparent if one recalls that snap-off is the most important microscale phenomena leading to oil trapping in porous media during secondary waterflooding. The formation of water-in-crude oil emulsions during crude oil production poses major problems for both process and product quality viewpoint. In contrast, emulsions have been found to benefit oil recovery in enhanced oil recovery (EOR) processes,particularly during chemical flooding. Understanding emulsification and emulsion stability is essential to elucidate mechanisms involved in EOR and also to attain optimum phase separation in production operations. Presence of an emulsifying agent is essential to form stable water-in-oil emulsions. Asphaltenes indigenous to the crude oil have been proposed as the main contributing agent to emulsion stability by the formation of a viscoelastic film at the oil-in-water interface. However, fine solids such as scales and clay particles, added chemicals, and other crude oil components such as naphthenic acids may also contribute to the stabilization. The objective of this research is to ascertain the impact of water chemistry on fluid-fluid interfacial behavior. Time evolution of emulsion drop-size distribution is employed as a tool to probe the interface and as a proxy for emulsion stability. The effect of naphthenic acids and polar components such as asphaltenes on film formation has been studied as a function of water chemistry and time. Nuclear magnetic resonance (NMR) spectroscopy is utilized to detect the naphthenic components in aqueous phases in contact with crude oil and an interfacial rheological technique is applied to investigate the kinetic of film formation. At the conclusion of this dissertation, suppression of snap-off is introduced as one of the controlling mechanism during secondary low-salinity waterflooding. This hypothesis has been examined through a series of coreflooding experiments. This dissertation has established connections among several interfacial processes that affect crude oil recovery and emulsion stability.