There are many causes for poor oil recovery but the physical factors are by far the most critical in determining the efficacy of recovery. These inculde
- Existence of the Interfacial Tension between oil and water and Wettability (Capillary Forces)
- High mobility ratio between water and oil (viscous forces)
Oil recovery is typically done in a two-step process: primary and secondary. The average primary recovery rate is around 15-18 % of the estimated oil in place. This percentage depends on the method used to extract the oil and the properties of rock and the oil itself. The secondary recovery may enhance the output to 30 %. The remining 70% reservoir are the target of the enhanced oil recovery methods (EOR).