Fluid flow through shale gas reservoirs: Simplified conceptual and mathematical models

Following the increasing global energy demand and oil prices, gas production has attracted the energy firms significantly. Apart from the natural gas production from conventional reservoirs, production of shale gas from unconventional reservoirs has contributed significantly in meeting the global energy demand despite its environmental impacts. Albeit the focus on hydro, solar, wind, nuclear and geothermal powers, the dependence on fossil fuels in the form of natural or shale gas still remains inevitable in the context of meeting the growing energy demand. However, the estimation and production of shale gas from an unconventional reservoir poses a lot of challenges throughout the production period. In particular, only a particular model is widely used to describe the shale gas adsorption-desorption mechanism irrespective the complex geology associated with the shale gas reservoir. In this context, a sensitive table has been deduced that clearly distinguishes the fundamental differences of gas extraction from a conventional gas reservoir from that of an unconventional shale gas reservoir. Next, a possible list of queries that remain unanswered in the context of field-scale shale gas estimation and production. Third, a detailed list of complexities associated with the development of the conceptual model has been listed. Fourth, a relatively simpler conceptual model along with its associated mathematical model has been deduced to estimate the shale gas concentration. And, finally, a detailed set of various sorption isotherm models have been gathered that will suit the varying nature of a complex shale gas reservoir. Thus, the study is expected to provide field-scale limitations associated with the estimation and production of shale gas from a shale gas reservoir, and it will subsequently aid in deducing better shale gas reservoir management decisions.