An inversion scheme to model subsurface fracture systems using shear wave splitting polarization and delay time observations simultaneously

Abstract

Shear wave splitting polarization (p) and delay time (Δt) observations are used to invert for fracture orientation and intensity of fracturing, simultaneously. By addressing the different levels of uncertainty involved in measurements of these two parameters, as well as their dissimilar relationships to fracture configuration, we have developed an inversion algorithm which reduces the primary double-response inversion to two connected single-response ones. We show that its inherent non-linearity complicates this problem, which therefore requires a more sophisticated attack than conventional inversion schemes. It will be shown that the construction of residue function contours in the model plane and the generation of surrogate data by simulation process are essential to this approach. We illustrate the capabilities of this technique by inverting shear wave splitting data from The Geysers geothermal reservoir in California. In principle the method should be useful for characterizing fractured reservoirs, whether geothermal or hydrocarbon. © 2005 RAS.