Patent ID: 9720129
Date: 2017-08-01
CPC Classifications: E21B,G01V,H02J,H04L,H04W

Claim:
1. Apparatus for measuring electrical conductivity of a rock formation surrounding a wellbore, comprising: a housing adapted for operation of electronic apparatus in a wellbore; means for generating a linear amplitude modulated multi-amplitude sine wave at variable amplitudes enveloped within pulse compressed time intervals and pulse widths, wherein a phase accuracy of electronic circuits for generating sine wave and pulse signals is designed for stability over a range of wellbore temperatures; a differentially driven transmitter coil disposed at a selected location on the housing connected for receiving and transmitting the signals from the first electronic circuits; a plurality of mutually balanced fully differential receiver coils disposed at selected locations on the housing, each coil connected to second digitally-controlled electronic circuits for amplifying and filtering signals from the receiver coils; a phase-sensitive detector and low pass filter for receiving signals from the second electronic circuits and the first electronic circuits and producing in-phase and quadrature out-of-phase signals as an analog signal; and an analog-to-digital converter to process the analog signal and produce a digital signal for transmission.