Summary

We describe the results of monitoring several hydraulic fracture treatments in the Marcellus formation using two microseismic monitoring arrays: one deep twelve-3C-geophone array located in a vertical wellbore and a series of multi-component seismic sensors installed in a grid of 140 shallow boreholes. We combine the mapped microseismic events and associated attributes derived from the two arrays with conventional 3D surface seismic data to explain variations observed during the stimulation campaign. The mapped hypocentral locations are interpreted in conjunction with seismic-derived attributes. Inversion for acoustic impedance (AI) was carried out on the available pre-stack time migration (PSTM) stack, using one well which had a full suite of log data available for calibration. The resulting map of high to low AI correlates with microseismic activity. In addition, we combine lineaments representing fault and fracture systems derived from the seismic data. We examine well by well the relationship between microseismic data and indicators of structural and lithological changes provided by inverted AI cube. Extracted microseismic information includes geometry of the mapped event hypocenters, low seismically active stages, microseismic event attributes, and event clustering. After superimposing the inverted AI and the seismic-derived discontinuity volume with the mapped microseismic data, we observe that preferential fracture directions extracted from the mapped hypocentral locations agree with the natural fracture system oriented according to the dominant-stress tectonics. Low seismically active stages correlate with AI variations identifying potential presence of natural barriers. Mapped discontinuities are also confirmed to intersect some of the wells.

URTeC 1577327

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