Enhanced oil recovery through porous media: numerical analysis

The global increase in demand for petroleum and yet diminishing oil reserves have encouraged different methods of oil recovery. Enhanced oil recovery (EOR) is an essential strategy for oil retrieval for trapped oil, a concept developed due to low oil levels in the oil reservoir. It can be computationally analysed made possible by rapid technological advances for simulation studies. Computational fluid dynamics (CFD) assists in numerical analysis to understand the behaviour of pore configuration, changes in wettability, viscosity, interfacial tension (IFT) and contact angles in porous media. Realistic fracture configuration and its effects on the simulation and the oil recovery need to be investigated thoroughly. To study oil pore configuration, this research aims to create a realistic pore structure and effects of wettability, contact angle and IFT. A geometric arrangement of a laboratory sample and a simplified configuration are selected. These are numerically analysed with the multiphase volume of the fluid method, and subsequently these models are examined for saturated and unsaturated oil conditions. The result of saturated oil shows that if the contact angle is less than 90°, oil recovery is 96% or more, and if the contact angle is greater than 90°, then it is less than 96%. A saturated oil state is followed by an unsaturated state as some of the oil remains trapped within the rocks. Two different oil pore sizes were considered for examining the combined effect of low interfacial tension and alteration of wettability through nano-fluid flooding. This outcome demonstrates that 99% oil recovery is achieved for both unsaturated cases but it takes a longer time to recover oil from a smaller oil pore arrangement than a large oil pore. Unsaturated oil condition was also studied for 10, 35, 52, 65 and 75 μN/m IFT values and revealed that low IFT values amounting in 99% oil recovery are obtained for both configurations. However, complex geometry requires more recovery time when compared to the simple arrangement.