Inversion of microseismic data for triclinic velocity models

摘要: Modern downhole microseismic surveys often employ geometries in which ray trajectories generated by a collection of locatable events provide full polar and azimuthal coverage, making it possible to estimate the situ seismic anisotropy. We show that traveltimes particle motions direct P- shear-waves acquired such can constrain stiffness tensors triclinic media. While obtaining all 21 coefficients homogeneous space simultaneously with locating pertinent from data recorded single vertical well is relatively straightforward, same methodology does not necessarily succeed layered formations because combination their heterogeneity anisotropy might invalidate commonly adopted approximation event azimuths those P-wave polarization vectors. When cannot be derived motions, observed two or more wells are required locate build higher-symmetry azimuthally anisotropic velocity models. As our numerical tests indicate, multi-well event-location methods expected perform better than single-well counterparts they rely solely on triangulation eliminate usually pronounced uncertainties locations stem noises adversely affecting hodogram analysis.