Physics of unconventional shale gas reservoirs for a long-term production perspective

A simple unconventional reservoir model is developed that accounts for complex physics affecting production from hydraulically-fractured wells in shale resources. Integrating these physics and evaluating their order of importance on future production of an unconventional reservoir is very essential. The proposed model divides the formation into three zones, rock matrix (I), induced-fracture (II) and hydraulic fracture (III) that hold varying characteristics. Also, a history matching process with Marcellus shale field production data is performed in order to obtain the most uncertain parameters defined in the model. Results showed that combined effect of permeability losses of hydraulic and induced-fracture zones results in 15% gas production drop in 30 years. It is also concluded that the minimum ingredients required for long-term production forecast of unconventional shale gas reservoirs are considering two physics; shale surface methane desorption along with pressure-dependent permeability for fracture network and other physical phenomena are inconsequential.