Well logging apparatus having toroidal induction antenna for measuring, while drilling, resistivity of earth formations
First Claim
1. Apparatus for determining the resistivity of formations surrounding an earth borehole, comprising:
- an electrically conductive metal body movable through the borehole;
a toroidal coil antenna disposed on said body;
means for energizing said toroidal antenna to induce a current which travels in a path that includes said body and said formations;
an electrode disposed on said body; and
means for measuring at said electrode an electrical signal resulting from said current, said electrical signal being an indication of the resistivity of said formations.
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Accused Products
Abstract
Apparatus is disclosed for determining the resistivity of formations surrounding an earth borehole. An electrically conductive metal body, such as a drill collar on a drill string, is movable through the borehole. A transmitting toroidal coil antenna is disposed on the body and is energized to induce a current which travels in a path that includes the body and the formations. An electrode is disposed on the body, and an electrical signal resulting from said current is measured at the electrode to obtain an indication of the resistivity of the formations. In a disclosed embodiment, one or more electrodes can be mounted on a blade that is mechanically coupled to the body.
255 Citations
52 Claims
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1. Apparatus for determining the resistivity of formations surrounding an earth borehole, comprising:
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an electrically conductive metal body movable through the borehole; a toroidal coil antenna disposed on said body; means for energizing said toroidal antenna to induce a current which travels in a path that includes said body and said formations; an electrode disposed on said body; and means for measuring at said electrode an electrical signal resulting from said current, said electrical signal being an indication of the resistivity of said formations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A measurement-while-drilling system for determining the resistivity of formations surrounding a borehole being drilled in the earth by a drill bit at the end of a drill string, comprising:
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a drill collar in said drill string, said drill collar comprising an elongated tubular body formed of an electrically conductive material; a toroidal antenna mounted on said body in an insulating medium, said antenna comprising a coil mounted on a toroidal core having an axis substantially coincident with the drill collar axis; means for energizing said toroidal antenna to induce a current which travels in a path that includes said body and said formations; an electrode disposed on said body; and means for measuring at said electrode an electrical signal resulting from said current, said electrical signal being an indication of the resistivity of said formations. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
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Specification