Electromagnetic lithosphere telemetry system
Patent 4087781 Issued on May 2, 1978. Estimated Expiration Date: 
May 2, 1995. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
May 2, 1995. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesInventorsAssigneeApplicationNo. 682417 filed on 05/03/1976US Classes:340/853.7, Repeater in subsurface link (e.g., cable, etc.)340/854.5, Wellbore casing or ground340/854.6, Electromagnetic energy (e.g., radio frequency, etc.)340/855.5, Digital signal processing in subsurface transmitter455/40Earth or water mediumExaminersPrimary: Birmiel, Howard A.Attorney, Agent or FirmInternational ClassG01V 001/40AbstractA lithospheric electromagnetic telemetry system specifically adapted for telemetry of oil well drilling parameters from well bottom to surface of the earth. Sensors measure such parameters as pressure, temperature, salinity, direction of well bore, bit conditions, as well as the standard well logging parameters. The sensor outputs are converted to digital form and stored in a local memory until they are transmitted upon a triggering signal from a surface station. Transmission is accomplished by phase shift modulating an ELF (Extra Low Frequency) or ULF (Ultra Low Frequency) carrier, preferably in the range of 1-30 Hz. Repeater stations which delay and retransmit the signal are spaced along the oil well drill pipe as required. Both the well bottom station and repeaters are mounted inside the oil well drill pipe without substantially decreasing clearance for mud flow.Other References
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