Analysis of Microscopic Displacement Mechanisms of a MIOR Process in Porous Media with Different Wettability

The wettability of the reservoir rock has an important effect on the displacement of fluids on a microscopic scale in all EOR processes, especially in the microbial improved oil recovery (MIOR) process. This study describes the effect of wettability on microscopic two-phase flow displacement mechanisms of bacterial flooding. It enables us to get better understanding and prediction capability of macroscale flow behavior of the MIOR process. To achieve the goal, a number of visualization experiments have been carried out in glass micromodels with water wet and oil wet wettability status. Synthetic brine and model oil and an alkane oxidizing bacterium are used to explain the different behavior of microscopic displacement mechanisms in the water wet and oil wet micromodels. The results obtained in the two media are presented and compared. The observational results show the effect of wettability of porous media on remaining oil saturation and oil phase transportation. In water wet model, the oil is remained mostly as isolated drops while in oil wet model, the remaining oil is the continuous phase. The bacteria have the ability to displace the residual oil trapped in the micromodel. It is shown that the bacteria have various performances in the oil wet and water wet systems. The acting mechanisms supporting the displacement process are the interfacial tension reduction, wettability changes, and pore blocking.