Surfactants in Enhanced Oil Recovery

Abstract

The change in microemulsion phase behavior from contact with a laboratory crude oil (stock tank oil) to the contact by a live reservoir fluid is a combination of two effects. First the composition of the oil is different and there is also an effect of the change in pressure (Skauge and Fotland, SPE 14932) on the microemulsion phase behaviour. We have studied the effect of change in the molar volume of the oil on the phase behaviour of microemulsions. The experiments have been performed by changing the oil components with regard to both molecular weight and molecular structure. Static phase behaviour measurements have been performed at 22, 50 and 90°C. The changes in solubilization and optimal salinity are discussed in regard to the properties of the oleic phase. The effects of pressure (1–220 bar), and also the addition of gas (methane) have been determined. The change in phase behaviour with increase in pressure is found to be a function of the change in oil density versus pressure. Comparing the phase behaviour of alkanes or alkylbenzenes to that of a reservoir crude makes it possible to identify a synthetic oil having the same properties as the reservoir fluid.