Abstract: An MWD EM data/control telemetry link between down-hole instruments and ground surface instruments dynamically adapts to the underground electrical environment utilizing a down-hole microprocessor unit and a surface data processing unit (computer) each of which continuously monitors, probes and sweeps the frequency spectrum with EM signals to determine an optimum frequency for signal transmission between the respective units via either the drill string, the surrounding strata, or both, and then generates and digitally modulates a carrier signal at such optimum frequency with data/control signals.

Abstract: Measurement while drilling apparatus for detecting and communicating information relative to downhole parameters and/or characteristics of the earth strata via an electrically conductive drill string composed of a plurality of lengths of metallic pipe connected end-to-end in series and through which a drilling fluid is caused to flow and then return to the surface through the well cavity formed between the exterior wall of the drill string and the interior wall of the well comprising a DC voltage supply for establishing a unidirectional biasing current passing through the electrically conductive drill string, drill bit and surrounding earth strata, a colloidal suspension of ferro-magnetic particles coated with a non-conductive coating forming a part of the drilling fluid and carried by the drilling fluid through the well cavity wherein the ferromagnetic particles are caused by the magnetic field to migrate toward the outer surface of the drill string and to form an insulative coating thereon, a downhole modul

Abstract: A device for measuring the weight and torque on bit while drilling includes an outer bored cylindrical sleeve coaxially connectable into a drill string above a drill bit and an inner bored cylindrical sleeve welded coaxially within the outer sleeve. Strain gages located on the exterior surface of a necked-down section of the inner sleeve are isolated in an ambient pressure environment within annulus between the sleeves. Temperature compensation is accomplished by resistance temperature detectors sensing temperatures at the exterior surfaces of the respective sleeves.

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.