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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 su

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.

대표청구항 ▼

Information while drilling apparatus for detecting electrical data reflective of geological conditions generally ahead of a drill bit in a well and communicating such data to ground surface via an electrically conductive drill string comprising: excitation source means for inducing alternating elect

Information while drilling apparatus for detecting electrical data reflective of geological conditions generally ahead of a drill bit in a well and communicating such data to ground surface via an electrically conductive drill string comprising: excitation source means for inducing alternating electrical excitation currents to flow through earth strata surrounding the drill bit; an elongated, electrically conductive, cylindrical module forming a drill collar means connected in the drill string proximate said drill bit at the lower end of said drill string having, a passive current sensing means disposed at the lower end of said module for detecting excitation currents flowing to and from earth strata generally adjacent to and ahead of the drill bit through said drill bit and for developing corresponding logging signals, a first detecting means responsive to said logging signals and operative to develop corresponding first data signals, and a first signal coupling means for coupling said first data signals into said drill string; and communication means coupled to said drill string for receiving said first data signals; a bi-directional remote coupler means including, an electrically conductive cylindrical coupler housing forming a part of said conductive drill string above the module; a remote relay toroidal transformer means encircling a cross-sectional area coaxially within said coupler housing and having one lead of its toroidal winding electrically connected to said coupler housing; an insulated conductor of predetermined length electrically connected between the other lead of the toroidial winding and a wiper contactor contacting said module at a point below said first signal coupling means, said first signal coupling means inducing said data signals in said insulated conductor, said conductor communicating the data signals to said remote relay toroidal transformer means which in turn couples said data signals into said drill string.