Moment tensor inversion of perforation shots using distributed-acoustic sensing

Abstract

Distributed-acoustic-sensing (DAS) fibers have enabled various geophysical applications in unconventional reservoirs. Combined with perforation shots, a DAS fiber can record valuable guided waves that propagate in the reservoir formation and carry information about its properties. However, the representation of perforation shots as seismic sources, needed to conduct quantitative analysis, remains unknown. We model such sources using a superposition of three mechanisms for which we derive the moment-tensor (MT) representation. Using field DAS data recorded in the same well where the perforations are located, we establish a workflow to invert the resolvable components of the total MT for 100 different perforation shots. By scrutinizing the inversion results, we conjecture that the MT can indicate how effectively a perforation shot creates microcracks in the surrounding rock. Furthermore, we observe a regular spatial pattern in the inverted MTs, which correlates with the relative location of the perforation shot within each stimulation stage.