Patent ID: 6794875
Filing Date: 2004-09-21
Classification: G01V

Abstract:
A method of induction well logging comprising:transmitting a first signal at a frequency Æ’1 from a first transmitter coil; transmitting a second signal at a frequency Æ’2 from a second transmitter coil; transmitting a third signal at a frequency Æ’3 from a third transmitter coil; wherein each of said first, second, and third transmitter coils is energized with its own distinct input signal and wherein said first, second, and third coils comprise one or more elliptical conductive loops, each lying in a plane tilted substantially from the principal axis, each coil positioned symmetrically, about the principal axis, and each coil being centered on substantially the same point; receiving said first, second, and third signals at a receiver coil arrangement comprising three coils, each coil comprising one or more elliptical conductive loops, each loop lying substantially in a plane tilted substantially from the principal axis, each coil positioned symmetrically about, the principal axis, and each coil being centered on substantially the same point to receive said first, second and third transmitter signal; and recording each of the received signals, wherein said transmitted signals are generated by a digital waveform generator and said received signals are sampled at a rate r selected so that sampled signals are locked in phase with said transmitted signals; and further wherein N1 successive samples of said received signal are stored in a first set of accumulators, where N1 is an integer; N2 successive samples of said received signal are stored in a second set of accumulators, where N2 is an integer; and N3 successive samples of said received signal are stored in a third set of accumulators, where N3 is an integer; wherein said frequency Æ’1 is selected so that M1 complete cycles of said first signal are contained in said first set of accumulators, where M1 is an integer, where Æ’1=rM1/N1, N1/M1&gE;2, and where M1 and N1 have no common factors; wherein said frequency Æ’2 is selected so that M2 complete cycles of said second signal are contained in said second set of accumulators, where M2 is an integer, where Æ’2=r M2/N2, N2/M2&gE;2, and where M2 and N2 have no common factors; and wherein said frequency f3 is selected so that M3 cycles of said third signal are contained in said third set of accumulators, where M3 is an integer, where Æ’3=rM3/N3, N3/M3&gE;2, and where M3 and N3 have no common factors.