Phase behaviour of brine, decane and a surfactant chemical.

Polymers can typically be added to the injection water flooded through a reservoir to achieve IOR. The purpose of this additive is to block 'highways' for the injection water in the reservoir in order to change and optimise flow patterns.

With the other technique, surfactants (detergents) are added to injection water to 'wash out' more oil in the reservoir.
 
More specifically, polymers add to sweep efficiency by improving the mobility ratio. Surfactants, for their part, enhance microscopic recovery by reducing capillary forces in addition to boosting sweep efficiency.

Conventional polymers help to raise the viscosity of the injection water, whilst surfactants reduce interfacial tension between oil and water.

Statoil is currently screening various surfactants supplied by chemical manufacturers, and is also working with other industry stakeholders to develop more efficient and environment-friendly IOR chemicals.

The IOR potential of polymer flooding is being evaluated on the Dalia field off Angola, where Statoil is a partner.