Impact of Gas–Condensate Composition and Interfacial Tension on Oil-Repellency Strength of Wettability Modifiers

Abstract

Productivity of gas–condensate wells can significantly be declined as the condensate bank evolves around the wellbore. Wettability alteration of formation minerals from strongly liquid-wet to intermediate gas-wet conditions using liquid-repellent fluorinated chemicals has shown promising results to mitigate such liquid-blockage issues. This paper, for the first time, presents the results of unique contact angle measurements conducted on the treated carbonate substrates using synthetic gas–condensate fluids. The impact of hydrocarbon composition and interfacial tension (IFT) on the condensate wetting tendency was investigated using various binary and multi-component mixtures at ambient temperature. A high-pressure high-temperature (HPHT) drop shape analysis setup was customized to perform the static contact angle tests. The generality of the new findings from these measurements was also confirmed using dynamic unsteady-state flow tests. The results demonstrated that the wetting tendency of the condensate is significantly decreased as IFT increases and/or the hydrocarbon composition becomes heavier. The C1–nC4 condensate drop, for instance, completely wetted out the treated surface at both low- and high-IFT limits of 1 and 10 mN/m, whereas the C1–nC10 sample resulted in contact angles of 30° and 65° at similar IFT conditions, respectively. The oil-repellency strength of the fluorochemical was also evaluated at high temperatures of 50 and 100 °C with promising results. In this paper, the initial investigations on the impact of surface roughness on the solid surface wettability was carried out, demonstrating the positive impact of surface roughness on increasing the desired level of oil repellency achieved after the wettability alteration. The new findings from this work provide important guidelines in design and application of wettability modifiers for gas–condensate reservoirs.