Economic recovery of shale gas reservoirs requires effective hydraulic fracturing in order to stimulate production. In this paper, a case study is presented from the Montney Shale in NE British Columbia, where microseismic and reservoir characterization data were used to understand some of the constraints on the fracture geometry. The study found that when wells were close to pre-existing faults, the hydraulic fractures were found to interact with these faults and act as a barrier to fracture growth. The microseismicity associated with the fault activation was found to have relatively large magnitudes and anomalous frequency-magnitude characteristics. In cases where the wells were far from pre-existing faults simple, planar hydraulic fractures were observed. However, there was a tendency to grow towards regions of low Poisson’s ratio identified through amplitude versus offset inversion of the seismic reflection data, which are believed to correspond with lower stress regions. Integrating microseismic interpretations and fracture treatment data with enhanced reservoir characterization has been used to rethink well placement and completion designs, resulting in improved well performance.
Microseismic imaging of hydraulic fractures is a common diagnostic technology in all North American tight gas and shale gas fields. Fracture stimulation for enhanced permeability is a critical step for economic exploitation of these unconventional reservoirs. Microseismic imaging has shown that hydraulic fractures are much more complex than originally thought, with fractures often showing a high degree of depth containment and long fracture lengths. However, the injected fluid will follow a path of least resistance and depending on the stress conditions, may intersect pre-existing planes of weakness associated with either healed or open fractures. The resulting hydraulic fracture is therefore more complex than a single hydraulic fracture plane, often consisting of a network of both newly created hydraulic fractures and deformed pre-existing fractures in various orientations.
