The Impact of Reservoir Heterogeneity on Hydraulic Fracture Geometry: Integration of Microseismic and Seismic Reservoir Characterization
Economic recovery of shale gas reservoirs requires effective hydraulic fracturing in order to stimulate production. Microseismic imaging has shown that the hydraulic fractures often create complex fracture networks containing multiple fractures in various orientations. These fracture networks are often highly variable from well-to-well and even between frac stages in a single well. In this paper a case study is presented from the Montney Shale in NE BC, 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. Regions with the increased level of microseismic deformation and corresponding fault related source characteristics correlated with the presence of a pre-existing fault identified by edge detection/ant tracking algorithms applied to seismic reflection data. 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. The tendency for the hydraulic fractures to be asymmetric and grow preferentially towards the low Poisson’s ratio region is attributed to material property changes and associated lower stresses in these 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. The paper will describe the data integration steps that resulted in these conclusions, the impact of reservoir heterogeneity on hydraulic fracture geometry and describe the subsequent improvements with future well placements and fracing designs that resulted from these findings.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California