KARL FOX KIEFER
Pilots at Scatterwood Ct, Spring, TX

5467083, Nov 14, 1995

Aug 26, 1993

8/111915

William J. McDonald - Houston TX
Gerard T. Pittard - Houston TX
Charles G. Steele - Houston TX
Karl F. Kiefer - The Woodlands TX
Terry P. Clifton - Houston TX
Curtis E. Leitko - Houston TX

Electric Power Research Institute - Palo Alto CA

G01V 140

3408546

A wireless downhole electromagnetic data transmission system and method utilizes microprocessor controlled frequency synthesis for two-way communication between the surface and a downhole guided boring or drilling apparatus in the range of from 100 Hz to 100 KHz. A non-magnetic downhole probe unit connected between a drill motor or drill bit and the drill string contains data gathering and transmission components including accelerometers which measure the earth's gravity vector and fluxgate magnetometers which read the earth's magnetic field and serve as power line proximity sensors. The drill pipe acts as an electrical lossy, single conductor with the earth forming the electrical return path. Sensory data gathered by the downhole probe is encoded in digital format and impressed upon the drill string using frequency shift keying of the electromagnetic energy waves and is picked off at the surface by a signal receiver-demodulator and message processor unit. The surface unit instructs the downhole probe to transmit multiple frequencies and selects one or more frequencies with the most favorable signal-to-noise ratio(s) in response to local conditions to maximize the transmission distance at a selective frequency band range and given transmitter power level and baud rate.