Numerical Modeling of Microseismic Monitoring at the Second EGS Collab Testbed

Abstract

The EGS Collab project will continuously monitor microseismicity during shear stimulation of fractures at the second EGS Collab testbed at the depth of 4100 ft at the Sanford Underground Research Facility in South Dakota. The microseismic monitoring will use multiple wells surrounding the stimulation region with four accelerometers in each well, centered at the stimulation region. We conduct numerical modeling of the microseismic monitoring to understand what the optimal well separation distances/angles are. We perform location error analysis and moment-tensor inversion error analysis for four well setups with different geometries, controlled by parameters including wellhead locations of monitoring wells and the opening angle between two wells. We add Gaussian noise to synthetic traveltime picks and waveforms for event location and moment-tensor inversion analyses, to account for errors in the velocity models and traveltime picks. We determine the optimal well design by selecting a well geometry that provides balanced minimal errors in both event locations and moment tensors.