Evaluation of Reservoir Modeling in Shale Gas Reservoirs

Abstract

The economic development of shale gas reservoirs hinges on horizontal drilling and multi-stage hydraulic fracturing treatments. Hydraulic fracture geometry has a high uncertainty, which mainly depends on the shale brittleness. In soft shale formation, a bi-wing fracture model can be used to represent hydraulic fracture geometry; however, in brittle shale formation, a fracture network model is required. In addition, the orientation of hydraulic fractures in some cases is not perpendicular to the horizontal wellbore but with an angle. Furthermore, reservoir modeling in shale reservoirs is quite different from that in conventional reservoirs. An accurate reservoir model in shale reservoirs should take into account non-Darcy flow in hydraulic fractures, gas desorption effect and geomechanics effect (stress-dependent fracture conductivity). Hence, evaluation of reservoir modeling in shale reservoirs with different fracture geometry is desirable. In this work, based on typical fluid and rock data from Marcellus Shale, we use numerical simulation approach to investigate the impacts of non-Darcy flow, gas desorption and geomechanics on well performance. Also, we compare the bi-wing fracture model and fracture network model when performing history matching with field production data from Marcellus Shale. In accordance to the history matching results, the main fracture properties such as fracture half-length, primary fracture conductivity, secondary fracture conductivity, and fracture height and rock properties such as permeability are determined. The effect of different angles between hydraulic fractures and horizontal wellbore on gas recovery is studied. Finally, a robust reservoir model for shale reservoirs is obtained. This work is valuable for building an accurate reservoir model in shale gas reservoirs, and can provide critical insights for operators to optimize fracture treatment design.

AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014