Importance

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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 module for detecting downhole parameters and/or characteristics of the surrounding earth strata and for developing a communication current flow commensurate therewith in the conductive drill string, and a communication electronics coupled to the drill string at a point remote from the module for receiving the communicative current flow.

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First Claim