Investigation of wettability alteration through relative permeability measurement during MEOR process: A micromodel study

• MEOR experiments were conducted in aged glass micromodels.
• The impact of E. cloacae cells and its byproducts on wettability was investigated.
• Incremental oil recovery due to bacterial treatment was measured quantitatively.
• The results were confirmed by monitoring changes in relative permeability curves.

Microbial Enhanced Oil Recovery (MEOR) as a tertiary process employs microorganisms and their metabolites to reduce the residual oil saturation of the reservoir mainly through interfacial tension (IFT) reduction and wettability alteration. In spite of its great potential and the mentioned advantages, application of MEOR has been limited because of the lack of practical convincing experimental results. In this study, the effects of MEOR process on wettability changes and the reduction of residual oil saturation have been examined by providing microscopic visualization of two phase flow in transparent glass micromodels. Biosurfactant producing bacterial strain (Enterobacter cloacae) was utilized to investigate the impacts of both the biofilm and biosurfactant on wettability of the micromodel pore walls by measuring the relative permeabilities before and after microbial treatment. Results indicated that wettability of the pores was altered towards more water wetness which was also supported by visual observation of the oil/water phase saturations in the glass micromodel. Moreover, the oil recovery was increased up to 24.5% of the original oil in place (OOIP) during the MEOR process. At last, Biofilm formation was found to be more responsible for the wettability alteration process.