Statistical Netmoment Estimates of Q for Hydraulic Fracture Related Seismicity

Attenuation plays a major role in earthquake seismology affecting the way the seismic energy is dissipated during wave propagation. If not properly accounted for attenuation can bias calculations of earthquake source parameters and physical properties. We accurately estimate source parameters of micro-seismic events recorded during an hydraulic fracturing completion program in a shale reservoir and determine whole-path attenuation measurements for the region. We use a simultaneous inversion method (NetMoment) which takes advantage of the large number of recording sensors and of the commonality of the earthquake source to avoid biasing the source and attenuation measurements. We improved the accuracy in the NetMoment results by imposing constraints derived from the statistical analysis of the data. Our source results indicate that the micro-seismic events have on average low stress drops (1.5 MPa), lower than the stress drop of natural tectonic micro-earthquakes occurring in similar tectonic settings (~17 MPa), and follow self-similar scaling relationships. We observe that high frequency attenuation is variable within small volumes and its variability can be further used to improve geophysical models of hydrocarbon reservoirs and identify its three dimensional shape and regions saturated/depleted of hydrocarbons or fluids.