Research Note: Transverse isotropy estimation from dipole sonic logs acquired in pilot and production wells

Abstract

Dipole sonic logs acquired in near-vertical pilot wells and over the build section of nearby horizontal production wells are inverted to determine the five elastic constants characterizing a transversely isotropic formation, under the assumption of lateral homogeneity. Slowness values from a single depth in the vertical well are combined with data from the corresponding depth in the deviated well; these data are then inverted using nonlinear optimization to derive the five elastic constants. The technique is demonstrated on data from the Haynesville Shale in Texas. Estimates of the anisotropy are in line with a priori expectations; the Thomsen e and γ parameters are well correlated and generally possess positive anellipticity, with Thomsen’s e greater than Thomsen’s δ.