Modelling the effects of thermal gradient on microbe facilitated mineral precipitation kinetics in subsurface flow conditions

Abstract

Deep geological sequestration of anthropogenic carbon dioxide is a plausible way to reduce global greenhouse gas impacts. Long-term containment of sequestered CO2 can be achieved by preventing leakage and by ensuring further entrapments such as solubility-trapping and mineral-trapping. These processes can be enhanced by involving subsurface microbial community that restrict flows by forming biofilms and/favours biomineralization. For example, ureolytic bacteria, Sporosarcina pasteurii, catalyzes urea hydrolysis and accelerate calcite precipitations in presence of dissolved calcium ions. However, subsurface flows and reactions are complex and often involve multiple phases, chemicals and minerals as well as pressure and thermal gradients. These complex coupled behaviours are challenging and limitedly attempted. Within the scope of an ongoing study, a coupled numerical model has been developed under a THCM framework including subsurface microbial processes and associated bio-geochemical reactions. The model deals with liquid flow, multicomponent gas flows, dissolved chemicals and suspended microbes flows in liquid phase, heat flow, biofilms and minerals growths, mechanical deformations and geochemical/bio-geochemical reactions. In this paper, the coupled microbial model has been used to investigate the effects of thermal gradient on microbial growth and mineral precipitation as well as their overall impacts on the flow properties of the medium.