1. n. [Enhanced Oil Recovery]

An expansion in oil volume that can occur when a solvent contacts a reservoir fluid. The swelling is due to the complete or partial dissolution of the solvent molecules into the reservoir fluid. The amount of swelling is dependent on the pressure, temperature, composition and physical properties of the solvent and the reservoir fluid. Reservoir oil swelling can result in improved oil recovery by mobilizing residual oil trapped in inaccessible pore spaces.