Patent ID: 7990153

Claim:
A method for making a directional resistivity measurement in a subterranean borehole, the method comprising: (a) rotating a directional resistivity tool in a borehole, the directional resistivity tool including (i) at least first and second transmitting antennae configured to transmit corresponding substantially pure z-mode and x-mode electromagnetic waves and (ii) at least first and second receiving antennae longitudinally spaced from the transmitting antennae, the first and second receiving antenna configured to receive corresponding substantially pure z-mode and x-mode components of an electromagnetic wave; (b) causing the first and second transmitting antennae to sequentially transmit corresponding first and second z-mode and x-mode electromagnetic waves; (c) causing the first and second receiving antennae to receive substantially pure z-mode and x-mode components of each of the first and second electromagnetic waves transmitted in (b); and (d) computing a composite ratio of the z-mode and x-mode components received in (c).