Kerogen-rich shales are characterized by strong elastic anisotropy. When hydraulically fractured, they tend to become azimuthally anisotropic. As illustrated on a microseismic data set acquired in the Bakken Field, North Dakota, USA, accounting for azimuthal anisotropy of hydraulically treated formations yields several practical benefits. Those benefits include proper handling of the observed shear-wave splitting, improvements in the velocity model constructed to locate the microseismicity, and relocation and tightening of the cloud of recorded microseismic events. 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.

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