A surface complexation model of oil–brine–sandstone interfaces at 100 °C: Low salinity waterflooding

A temperature-dependent surface complexation model of oil–water–kaolinite interfaces allows theories of electrostatic links to petroleum adhesion to be tested with reaction path simulations. Petroleum adhesion to sandstone reservoir surfaces is controlled by coordination of carboxylic acids and nitrogen bases from the oil–water interface to charged sites at clay surfaces. While deprotonation of carboxylic acid groups should be relatively insensitive to temperature, deprotonation of nitrogen bases increases by over an order of magnitude between 25 and 100 °C causing a decrease in the pH of the isoelectric point of oil–water interfaces. Negative charge on clay edges and quartz also becomes more important with temperature. Of particular importance to enhanced oil recovery by low salinity water flooding is adhesion between anionic kaolinite edge sites and positively charged calcium-carboxylate and protonated nitrogen base groups present at the oil–water interface.

► We develop a model of oil-sandstone surface complexation at reservoir temperatures.
► We show how model oil-sandstone adhesion and release can be predicted.
► We use the model to identify mechanisms for low salinity waterflooding increase of oil recovery.