Smart water flooding

Low salinity and smart water flooding was introduced more than two decades ago. It began with laboratory tests in sandstones and has continued with carbonate rocks until today.

The method changes the fluid and rock/fluid characteristics to improve the conditions in a positive way to enhance oil recovery from carbonate rocks. In designed water flooding, all the components, such as crude oil, rock type, formation and the injected water, have their own roles in oil recovery in contact with the others.

One of the first proposed mechanism in low salinity flooding and smart water flooding in carbonate oil reservoirs is wettability alteration of rock surface. Other mechanisms such as ion exchange, IFT reduction between injected fluid and oil, mineral dissolution, and changes in surface charge should not be underestimated.

Actually, low salinity effect in carbonates is most like the result of a combination of mechanisms. A common factor in the mechanisms is that they release carboxylic acids of the oil from positive carbonate surface, which improve mobility of trapped oil.

The positive charge of carbonate rock surfaces is available for adsorption of deprotonated carboxylic acids (RCOO-) in the oil, which may lower the oil recovery potential, since it may prevent oil from flowing. The surface charges of the oil and rock is believed to be an important parameter.

The interface between the injected fluid and the oil is charged depending on the acidity of the oil and composition of injected brine. By an increase in the acid number (AN) of the oil, oil recovery from the carbonates might be reduced and the oil tends to stick to the rock surface. Several experiments have been conducted to investigate the effect of the ionic composition of smart water.

In this project, we attempt to conduct core flooding experiments to obtain special insight into injected brine ion composition in the tertiary stage. Also some preliminary tests will be conducted to figure out which brine works better in flooding.