A study of wetting behavior and surfactant EOR in carbonates with model compounds

A study on the mechanisms responsible for EOR from fractured carbonate reservoirs by surfactant solutions was carried out, and methods to quickly screen for effective chemical formulations quickly were examined. Adsorption of naphthenic acids on calcite surface in n-decane media was in the order: cyclohexanepropionic acid > cyclohexanebutyric acid > cyclohexanepentanoic acid. In terms of volume percentage of calcite powder floating on water, the oil-wettability of calcite powder treated with different naphthenic acids was in the order trans-4-pentylcyclohexane carboxylic acid ∼ cyclohexanepentanoic acid > cyclohexanebutyric acid > cyclohexanepropionic acid > cyclohexanecarboxylic acid. Contact angle and novel flotation test results were consistent in ranking oil-wet condition. The cationic surfactants were more efficient in recovering model oil from limestone core than the others, but one nonionic surfactant, Igepal CO-530, was efficient for oil recovery. The results of wettability alteration using different surfactant aqueous solutions in a simple flotation test were consistent with oil recovery by spontaneous imbibition of the selected surfactant aqueous solutions. This is an abstract of a paper presented at the 15th SPE-DOE Improved Oil Recovery Symposium: Old Reservoirs New Tricks A Global Perspective (Tulsa, OK 4/22-26/2006).