Evaluating the effects of velocity models and array configuration on induced seismic event locations in the Permian Basin
by
Xinding Fang, PhD
CTO of SensorEra
Dr. Xinding Fang received his PhD in Geophysics from MIT in 2013 and has 10+ years of experience in geophysics, petrophysics, and geomechanics and has participated in multiple projects related to seismic characterization, well logging, and geomechanical analysis. He worked at Chevron as a researcher in the Drilling Department 2014~2017 and spent 5 years at the University of Houston and SUSTech conducting research and exploring new technologies in many different areas such as multi-physics sensing technology and data fusion, internet-of-things (IoT) hardware and software development and advanced acoustic/seismic sensing technologies. He has a proven academic experience and is the author or co-author of over 70 research publications and multiple patents in the areas of seismic characterization, borehole geophysics, rock physics, and rock mechanics. He received the 2019 SEG J. Clarence Karcher Award in recognition of his excellent contributions to exploration geophysics.
Abstract
State-wide monitoring of induced seismic events mainly relies on public regional seismic arrays, which are composed of seismic stations that are normally tens of kilometers apart from each other. Accurate hypocenter determination of the induced events is crucial as it provides insight into the triggering mechanism, enabling operators and regulators to develop effective mitigation strategies. However, there are debates regarding the accuracy of the publicly reported induced event data due to discrepancies between public reports of event hypocenters and those determined using local dense arrays operated by private companies. The primary objective of this study is to identify the underlying causes of the discrepancies between results obtained from the public regional array in West Texas and local dense arrays. Through modeling and analysis of field data collected by a local dense array in the Permian Basin, we determine that three critical factors influence the reliability of induced event results. First, the accuracy of the velocity model used for event location is the most crucial factor. Second, the distance between a station and an event plays a crucial role in determining the sensitivity of the data to the hypocenter depth. Finally, consistency between the observed and modeled wave propagation behavior is crucial for ensuring the validity of the objective function in the inversion. Our findings indicate that it is challenging to obtain reliable hypocenters using a regional sparse array with station spacing on the order of tens of kilometers. The best practice for obtaining accurate event hypocenter and magnitude is to monitor induced seismicity using a local dense array and process the data with a velocity model that fully characterizes the local basin’s geology.
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