Assessment of hydraulic fracture complexity and stress field variability in an unconventional reservoir from composite moment tensor of double-couple microseismic events

摘要

Hydraulic fracturing generally creates a network of fractures of variable orientations and sizes, which depend on the pre-existing stress field and prevailing geomechanical conditions in the stimulated volume. We demonstrate that the compensated linear vector dipole of the composite moment tensor and the seismic consistency of induced microseismic events can be used to characterize fracture complexity and stress field variability in the stimulated volume. In the case study presented, the group of micro-earthquakes is dominated by strike-slip events with N-S striking rupture planes, resulting in a small CLVD component in the composite moment tensor. Nevertheless, the presence of few events with different mechanism types suffices to lower the value of the seismic consistency for the study volume. This demonstrates how sensitive this parameter is to variations of the stress field. The so inferred hydraulic fracture complexity may be used to evaluate the effectiveness of the stimulation, from which implications for well production can be inferred, and strategies for field management developed.