Waterflooding is now recognised throughout as involving a number of coupled chemical and physical processes, whereby interactions at the surface dominate. Previously published studies have mainly concentrated on sandstone reservoir systems but a significant volume of remaining reserves are held however in carbonate reservoirs. It is therefore particularly important to understand the surface of calcium carbonate (CaCO3, calcite) and its interactions with oil/water. The interface of calcite and water or oil is of paramount importance not only in oil recovery, but also a number of key academic and industrial areas such as scale deposition in domestic and industrial situations and controlled growth of biogenic skeletons. To enhance understanding of this key mineral, the calcite-liquid interface and adsorption of key organic compounds have been investigated using the novel technique of neutron reflection. This technique has proved to be an outstanding approach for the study of several particular solid/liquid interfaces allowing investigation of interfacial layers with molecular precision. This is the first time this method has been applied to the important calcite interface. Here we present initial results clearly highlighting the detailed insight this approach can provide. We observe adsorption of monolayers, bilayers and multilayers of the same surfactant with different conditions (concentration, solvent, counter-ion), ordering of the continuous phase near the interface and adsorption of polymers. We can identify enhanced surface dissolution by certain additives. The structure and composition of the adsorbed layers can also be described.
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