Fundamentals of crystallization at oil-brine interfaces for conformance control and oil spill remediation applications

Abstract

We have investigated the interfacial properties at a brine-hydrocarbon boundary with the prospect of understanding the crystallization process that takes place when certain electrolytes are present in the brine and when certain surfactants are present in the hydrocarbon phase. Solutions of nine cations and five carboxylic acids were investigated. We found that some combinations of electrolytes and acids than others are solidified at the brine-hydrocarbon interface. These interfacial phenomena were studied with an optical force tensiometer setup with a so-called buoyant droplet configuration. aim to utilize these specific interfacial formed crystals to design a method to form crystal plugs in high-flow sections (e.g., at fractures) of an oil reservoir. Ultimately, our studies target a real reservoir environment and we have included a range of different crudes with varying total acid numbers (TAN) and viscosities to bring the study a little closer to a realistic upstream setting. The electrolyte-surfactant combination that gives rise to the most clear-cut formation of crystals directly at the interface is involving Zn2+ or Cu2+ and dodecanoic acid (C11H23COOH). Several of the systems under study appears to be forming crystals within the hydrocarbon phase; these crystals are more likely a result of the surfactant-associated diffusive transfer of cations into the hydrocarbon phase with subsequent complexation. When it comes to the crudes, the findings are somewhat more complex, the acidity of the oil, not surprisingly, influences the interfacial properties including the crystallization propensity. The relationship between one-dimensional parameters such as TAN and crystallization propensity is not straightforwardly interpreted but it does seem like proper spiking can induce crystallization in most oils and that it is most favorably done in light oils where the diffusivity of the acids is largest. We have made the applicational space wider by also showing that the crystallization/interfacial phenomena can induce confinement of oil on a water surface; an observation that opens applications in oil spill remedies.