Microseismic hydraulic fracture imaging in the Marcellus Shale using head waves

We studied microseismic data acquired from a geophone array deployed in the horizontal section of a well drilled in the Marcellus Shale near Susquehanna County, Pennsylvania. Head waves were used to improve event location accuracy as a substitution of the traditional P-wave polarization method. We identified that resonances due to poor geophone to borehole coupling hinder arrival time picking and contaminate the microseismic data spectrum. The traditional method had substantially greater uncertainty in our data due to the large uncertainty in P-wave polarization direction estimation. We also identified the existence of prominent head waves in some of the data. These head waves are refractions from the interface between the Marcellus Shale and the underlying Onondaga Formation. The source location accuracy of microseismic events can be significantly improved by using both the P-, S-wave direct arrival times and the head wave arrival times. Based on the improvement, we propose a new acquisition geometry and...