Crude Oil Surface Active Species: Consequences for Enhanced Oil Recovery and Emulsion Stability

Abstract

The physical chemistry of the brine–crude oil interface is immensely complex as a result of the complexity of the crude oil itself, and access to the detailed phenomena occurring at this interface is extremely difficult. Understanding these phenomena is however of paramount importance because they are underlying issues encountered in several domains of the oil industry: reservoir flooding, oilfield emulsion production, so-called “flow assurance”, oil sands processing, emulsion formation in refineries, etc. These problems have prompted a number of studies in academic and industrial research laboratories. A large body of data has been generated, particularly in the areas of oilfield emulsion production and dewatering of bitumen extracted from oil sands by water processing. In the first part, questions raised and experimental observations made in reservoir flooding are presented. Some new results in this area are also offered that may shed some light on phenomena previously described in studies directed toward the dewatering of bitumen removed from oil sands. The spontaneous formation of water microdroplets in the oil phase when gently contacted to water is an example. In the second part, the literature on oilfield emulsion production problems is briefly reviewed, with the limited aim of extracting some features that could be in resonance with reservoir flooding. Roughly, two main types of vision of the mechanisms ruling the partitioning of asphaltenes, resins, and naphthenic acids between the interfacial pseudo-phase and the water and oil phases are encountered: (1) the complex formation model and (2) the competition model between these species. Experimental results supporting these models are given. Interestingly, both visions can be reconciled in a recently proposed model inspired by analogy with the protein film structure. This model also incorporates the experimental observations on the reversibility/irreversibility of asphaltene adsorption at the interface. More specifically, it is observed that the knowledge, tools, and technologies developed in both areas of reservoir flooding and oilfield emulsion production complement each other. The effect of the asphaltene concentration on interfacial properties is another example.