Large-Scale Modelling of Microbial Activities Underground

There are various examples of large-scale microbial activities in the subsurface. For instance, microbial reduction of sulfate to hydrogen sulfide (reservoir souring) is a known problem in oil and gas reservoirs. Moreover, geological storage of carbon dioxide in depleted hydrocarbon reservoirs can trigger some microbial pathways and inhibit some others inside the reservoir. The possible leakage of geologically stored carbon dioxide to the seabed environment can also affect microbial life in the seabed and groundwater layers in the overburden. A proper understanding of such processes requires the capability of reliable large-scale modelling of microbial and chemical activities underground. Such a modelling tool should consider not only various Thermo-Hydro-bio-Chemical (THbC) processes but also the numerical challenges associated with the simulation of large-scale complex media, such as upscaling reaction rates, numerical stability, and computational costs. This work presents a novel THbC model, the capabilities of which is demonstrated for a specific case of reservoir souring in an oil field in the Danish North Sea through the comparison of the simulation results with the field data. The results demonstrate the importance of matching against the production history of not just the final product of interest, but also other effective species.