Hydraulic Fracturing and Enhanced Recovery in Shale Reservoirs: Theoretical Analysis to Engineering Applications

Shale reservoirs are extensively exploited using hydraulicfracturing,which forms multiple cracks that connect with the existing naturalfractures to create a continuous path for the gas stored in the kerogento flow to the production well. Apart from the tedious nature of hydraulicfracturing, the mechanism of the storage and flow of gas is equallycomplex since multiple phases and scales are involved. An accurateunderstanding of hydraulic fracturing coupled with a strategy of analyzingthe flow and overall recovery of gas is paramount to ensure efficientexploitation. In this work, a comprehensive review of the recent strategiesused in analyzing the hydraulic fracturing, storage, flow, and recoveryof gas is presented. To begin with, the experimental, analytical,and numerical approaches pertinent to hydraulic fracturing are deeplyexplored. Additionally, the flow of gas through the newly opened channelsis accounted for by using a quadruple-domain approach where the mechanismsof flow in shale reservoirs at the nanoscale, microscale, mesoscale,and macroscale are considered. Furthermore, a strategy to capturethe multiple phases, including gas, oil, and water, and recover bothcarbon dioxide and methane is explored through thermal and enhancedgas recovery approaches. This review provides a baseline for understandinghow the hydraulic fracture evolves and propagates to create new channelsthat contribute to the flow of gas, how the gas flows through thecreated channels across the many scales of the shale reservoir, andhow to improve recovery from shale reservoirs.