Patent ID: 9581721
Date: 2017-02-28
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 first and second transmitters and first and second receivers axially spaced apart from one another, each of the first and second transmitters and first and second receivers including an axial antenna and collocated first and second transverse antennas, the first and second transverse antennas in the first receiver being rotationally offset by a predefined angle from the first and second transverse antennas in the first transmitter; (b) acquiring a plurality of electromagnetic voltage measurements from the first and second receivers while rotating in (a); (c) processing the voltage measurements acquired in (b) to compute harmonic coefficients; (d) mathematically rotating the harmonic coefficients through at least the predefined angle to obtain rotated coefficients; and (e) processing ratios of selected ones of the rotated coefficients to compute gain compensated measurement quantities.