Communications: electrical – Wellbore telemetering or control – Pulse or digital signal transmission
Patent
1982-09-30
1986-03-25
Jordan, Charles T.
Communications: electrical
Wellbore telemetering or control
Pulse or digital signal transmission
166 66, 175 50, 324342, 324356, G01V 100, G01V 310, E21B 2902
Patent
active
045786755
ABSTRACT:
An information while drilling apparatus and method for characterizing strata in the vicinity of a drill bit at the lower end of a drill string, including a down-hole module unit and surface receiving and control units. Excitation currents are caused to pass through the drill string, drill bit and surrounding strata and the current flowing through the drill bit is sensed by a first toroidal transformer that encircles the drill string immediately above the drill bit. The sensed current, which characterizes the strata adjacent to and below the drill bit, is detected to form logging signals. A second toroidal transformer couples the logging signals to the electrically conductive drill string for transmission to the surface receiving unit. The frequency of the excitation current is adjustable to permit characterization of the strata at various distances from the drill bit. The frequency of the transmitting signal is also adjustable to compensate for varying degrees of signal attenuation along the transmission path. Control of the excitation and transmission frequencies is effected by communications from the surface control unit in response to stored operating instructions or operator inputs.
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Hamrick Claude A. S.
Jordan Charles T.
MacLeod Laboratories, Inc.
Steinberger Brian S.
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