LAUSR

Abstract The advent and advancement in hydraulic fracturing techniques have resulted in the rapid growth of unconventional shale oil and gas production over the last couple of decades. Unlike conventional hydrocarbon systems, these shale formations serve as both the source and reservoir and therefore are directly drilled into for hydrocarbon production. Studies in different shale basins have revealed that these reservoirs are geologically complex, heterogeneous, and every play is unique. Therefore, for efficient hydrocarbon recovery, physicochemical, and mechanical attributes of individual shale reservoir need to be taken into account. Even after significant technological advancements, we are still struggling to understand the spatiotemporal variations in type and amount of hydrocarbon produced within a single basin, rapid declines in hydrocarbon production, and the low fracturing fluid recovery rates. In this review article, we briefly summarize how biogeochemical tools can be used to 1) understand variations in the quantity of organic matter (OM) that ultimately controls production of hydrocarbon, 2) determine variations in the quality of OM that ultimately controls the quality and type of hydrocarbons generated, 3) predict the fracturing potential of rock, and 4) increase efficiency of hydrocarbon production by controlling the water-rock-microbe interactions that ensue after hydraulic fracturing fluids are injected into the shale reservoirs. A better understanding and utilization of these biogeochemical processes and tools will help identify sweet spots for shale gas drilling, increase hydrocarbon recovery and open up the possibility of engineering the hydraulic fracturing fluids to enhance recovery and life of these shale reservoirs.