Azimuthal anisotropy in microseismic monitoring: A Bakken case study

Abstract

Hydraulic fracturing, routinely applied for enhancing the permeability of unconventional oil and gas reservoirs, is one of the possible causes for azimuthal anisotropy of the treated formations. Accounting for both naturally occurring and completion induced azimuthal anisotropy leads to marked improvements in the results of microseismic data processing. As illustrated on a data set acquired in the Bakken Field, North Dakota, USA, those improvements include the possibility of modeling the observed shear-wave splitting, reduction of misfit between the picked and modeled traveltimes of microseismic events, and relocation and tightening of the spatial distribution of the event hypocenters. In addition and perhaps most importantly for the development of microseismic technology, the feasibility of joint inversion of field microseismic data for the event locations and azimuthally anisotropic velocity model containing triclinic layers is demonstrated.