Abstract

The data we analyzed are from a Marcellus Shale gas field in Greene County, southwestern Pennsylvania. We first investigated the relationship between microseismic event trends and discontinuities extracted from 3D seismic data and their relationship to SHmax. This analysis was followed by an examination of the relationship of cumulative gas production to radiated energy, stimulated reservoir volume (SRV), and energy density (ED). We have determined that microseismic event trends observed in multiwell hydraulic fracture treatments were similar to the trends of interpreted small faults and fracture zones extracted from 3D seismic coverage of the area. Hydraulic fracture treatments conducted in six laterals produced clusters of microseismic events with an average trend of N51°E and, to a more limited extent, N56°W. The N51°E microseismic event trend coincided closely with the average N52°E trend of interpreted minor faults and fracture zones extracted from the 3D seismic data. That relationship suggested that microseismic events form through reactivation of old faults and fracture zones in response to an easterly trending SHmax. We also found that variations in gas production correlated with variations in radiated microseismic energy (R2 of 0.985), SRV (R2 of 0.974), and ED (R2 of 0.989). SRV is a measure of the volume of space occupied by induced microseismicity, whereas energy release per unit volume (ED) can be directly related to rupture area created through hydraulic fracture stimulation. We suggest that ED serves as a better estimator of production potential in unconventional shale reservoirs.

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