Effect of Wettability on Vaporization of Hydrocarbon Solvents in Nano Capillaries

Abstract

Abstract Tight rock reservoirs have gained popularity and become a subject of great interest due to their huge recovery potential. A substantial portion of the potential hydrocarbon could be removed from the reservoir by injecting solvent gases (hydrocarbon or CO2) as an Enhanced Oil Recovery (EOR) application. Achieving a precise modeling of these processes and accurate description of hydrocarbon dynamics requires a clear understanding of phase-change behaviour in confined (capillary) medium. It was previously shown that early vaporization of liquids could occur in channels that were larger than 1000 nanometers. The surface wettability plays a critical role in influencing the vaporization and condensation nature in confined systems. This paper studies the influence of the medium wettability on phase-transition temperatures of liquid hydrocarbons in macro (> 1000 nm) and nano (< 500 nm) channels by using different types of rock samples. The boiling temperature of hydrocarbon solvents was measured in two extreme wetting conditions: (1) strongly water wet, and (2) strongly oil wet. Boiling temperatures of heptane and octane in sandstone, limestone, and tight sandstone were observed to be lower than their bulk boiling points by closely 13%, on average. Altering rock wettability characteristically changes the average hydrocarbon nucleation temperatures being as critical as the pore size. The experimental outcomes also showed that reducing the solvent adsorption on clays in Berea sandstone lowers the nucleation temperature of heptane and octane from their normal phase-change temperatures by 30%.