Seismic Anisotropy Characterization in Heterogeneous Formations Using Borehole Sonic Data

Abstract

Abstract Inverting borehole sonic data for anisotropic elastic parameters requires data acquired in, at least, two different orientations. In practice this often means combining acquisitions from two offset wells, which is only straightforward if the encountered formations are laterally continuous. If wells do not tie laterally, or if data acquired at different depths in vertically heterogeneous strata need to be combined, then an inversion strategy is required that explicitly takes heterogeneity into account. This short note outlines such a strategy on the basis of borehole sonic and conventional petrophysical data, structural information, and well surveys. A new and sophisticated workflow was developed to estimate TI anisotropic parameters from borehole sonic logs, adopting a smart data clustering approach. Among other things, the output consists of elastic properties as a function of independently acquired data such as shale volume and density. In turn, these expressions constitute a model that is driven by measurements instead of assumptions, that can be established also in the presence of lateral and vertical heterogeneity, and that can be applied in neighboring wells where the amount of sonic data are insufficient for a complete inversion.