A review of recent developments and challenges in shale gas recovery

Over the past decade, there has been increased interest in shale gas plays worldwide. This is due to improved techniques in shale gas recovery from these ultra-low (in the order of hundreds of nanodarcies) permeability formations which is owed primarily to horizontal drilling, hydraulic fracturing and other technological advances. Another attraction to the exploration of shale gas is the lower inherent risk associated with its exploration when compared with exploring for conventional hydrocarbons due to its ubiquitous abundance wherever it is present. This success has indeed driven down gas prices and has culminated in the security of gas supply worldwide for decades to come.

This paper is a critical literature review of shale gas that identifies and examines challenges encountered in shale gas recovery which include inadequacies in mathematical flow models applied in shale gas modelling due to non-darcy flow, uncertainties in the fracture intensity, fracture symmetry and orientation and lack of standard protocols to mention a few. It also takes a look at how hydraulic fracturing improves the economics of shale gas exploitation since it considerably increases production and also the overall recovery from the reservoir. Hydraulic fracturing has come as the primary mode of increasing recovery in shale gas reservoirs but it also comes with its own problems where desired results are easily achieved in brittle shale formations but may be even more challenging for ductile shale formations. Another progress made is being able to monitor the fracture growth within the reservoir real time to prevent the fracture growing out of control.

Milestones are continually being achieved on improving the recovery of shale gas and in this paper we address progresses made and challenges encountered.