Patent ID: 9618647
Date: 2017-04-11
CPC Classifications: G01V

Claim:
1. A method for making downhole electromagnetic logging while drilling measurements, the method comprising: (a) rotating an electromagnetic logging while drilling tool in a subterranean wellbore, the logging tool including a plurality of transmitter antennas and a plurality of receiver antennas symmetrically spaced along a logging while drilling tool body, the plurality of transmitter antennas including at least one axial transmitter antenna and at least one transverse transmitter antenna, the plurality of receiver antennas including at least one axial receiver antenna and at least one transverse receiver antenna; (b) acquiring a plurality of electromagnetic voltage measurements from the plurality of receiver antennas while rotating in (a); (c) processing the voltage measurements acquired in (b) to compute harmonic voltage coefficients; (d) processing ratios of selected ones of the harmonic voltage coefficients to compute gain compensated symmetrized and anti-symmetrized quantities and angles; and (e) processing the gain compensated symmetrized and anti-symmetrized quantities and angles to compute rotated symmetrized and anti-symmetrized quantities, the rotated symmetrized and anti-symmetrized quantities being rotated to align with heterogeneities of a subterranean formation surrounding the wellbore.