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Abstract We present an integrated interpretation of microseismic, treatment, and production data from hydraulic fracturing jobs carried out in two adjacent wellpads in the Horn River Basin, Northeast British Columbia, Canada. Wellpad I includes 8 wells which were drilled and fractured in the Muskwa and Otter Park formations (4 wells in each formation) in 2010. Wellpad II includes 3 wells drilled and fractured in each of the three shale formations, Muskwa, Otter Park, and Evie, in 2011. There is one-year interval between fracturing of the first and second wellpads.
We studied magnitudes, b-values, moment tensor inversion, and the spatial and temporal distribution of three-component microseismic events recorded during more than 200 stages of fracturing by multi-well downhole-arrays. We analyzed Gutenberg-Richter frequency-magnitude graphs for each fracturing stage, and with proper integration of b-values, fracture complexity index (FCI), moment tensor inversion information, and treatment data, we distinguished hydraulic fracturing-related events and events associated with slip along the surface of natural fractures. The results are compared with five-year gas production data in each well.
Our results show the effects of natural fracture network on well-connectivity as well as spatial distribution of microseismic data. We show that hydraulic fracturing and production from wellpad II lead to interference with wells already producing from wellpad I. The integrated study indicates that hydraulic fracturing and production from wellpad II is the main source of four months of anomalous production decline in wellpad I. This anomalous production decline started about two months after hydraulic fracturing in wellpad II. We also show that the tendency of microseismic distribution in wellpad II toward wellpad I is due to the connection of the two wellpads through a network of pre-existing natural fractures, which are approximately parallel to the largest principal compressive stress in the area.
Both identification of natural fractures and information about interactions between hydraulically fractured wells are essential for optimum well placement and completion, reservoir characterization, stimulated reservoir volume calculation, and reservoir simulation. This study presents a distinctive insight into integrated interpretation of microseismic events and production data to identify the activation of natural fractures and interference between the hydraulically fractured wells.
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