Influence of Petroleum Acids on Gas Hydrate Wettability

Previous work has demonstrated that petroleum acids in some cases are able to convert systems with an initially high risk of hydrate plugging into easily flowable hydrate dispersions with low or no risk of plugging. In this work, we aim to identify the specific properties of the petroleum acids that make such a conversion possible. Petroleum acids are extracted from crude oils with anti-agglomerating hydrate behavior and fractionated into subfractions of different polarity by the use of solid-phase extraction. The separate effect of these subfractions on hydrate wettability is compared to the effect of the acid fraction as a whole, as studied by means of phase inversion in crude oil/brine emulsions. The results show that some acid subfractions display equal or even higher hydrate surface activity compared to the bulk acid matrix from which they are isolated. One of the subfractions displays an exceptionally high effect at low concentrations. Intermolecular effects may be of importance for the degree of effectiveness of the hydrate surface-active components. The acid fractions impose no or insignificant effects on lowering the interfacial tension between oil and water, implying that they are active at the hydrate-oil interface rather than the water-oil interface.