“Multicomponent induction response in a biaxially anisotropic formation,” SEG Annual Conference, San Antonio, Texas, USA, August 2007.
Advances in multicomponent induction logging data acquisition and processing make possible the characterization of biaxially anisotropic formations. However, understanding of induction response in a biaxially anisotropic formation lags behind. In this paper, analytic formulas are proposed that allow us to quickly model multicomponent induction responses in a biaxially anisotropic formation. The formula is accurate for the coaxial component and the ones for the coplanar components are reasonably accurate over the entire range of relative dip angles. The theory suggests that for a tool tilted in the xoz plane, the XX- and YY-responses are affected primarily by Rx and Rz and have little dependence on Ry, the resistivity normal to the tool deviation plane. An immediate observation made from the theory is that in a vertical and near vertical well, a full tensor measurement may not be sufficient to resolve a biaxially anisotropic formation. Measurements at higher frequencies must be made to resolve the ambiguity.