Subsurface formation parameters from tri-axial measurements

摘要

Systems and methods are provided for determining various subsurface formation parameters from electromagnetic measurements. Formulas are disclosed for field components in a coordinate system tied to the logging tool. Closed form expressions for a magnetic field distribution in a homogeneous anisotropic medium are derived from Moran-Gianzero formulas. A complete coupling of a tri-axial system of transmitters and receivers is derived in the tool coordinate system, allowing direct inversion of the measurements for horizontal and vertical conductivity and dip and strike (dip-azimuth) angles. Closed form expressions for these four quantities in the low frequency limit are also derived.