Apparatus for measuring the diameter of a borehole
AssigneeDresser Industries, Inc.
InventorHeinz D. Lichtenberg
Life of this patent
Estimating the term…
Abstract
A well logging instrument has a plurality of contact arms which are forced against the sidewall of the borehole. The contact arms are pivotally attached to a first collar fixed to a central shaft and are pivotally attached to a second collar slidably mounted on the central shaft. Radial movement of the center of the contact arms moves a slidable collar member over an electrical coil assembly emitting an alternating magnetic flux field. The movement of the slidable collar over the electrical coil assembly alters the eddy current loading of a coil. The position of the contact arms and thus the position of the slidable collar attached thereto can be measured by detecting the eddy current loading of the coil.
Claims9
A borehole caliper apparatus comprising:
- an elongated body member adapted to traverse said borehole;
- and electric coil assembly including first and second electric coils mounted within a section of said body member for simultaneously emitting an alternating magnetic flux field around each of said coils of said coil assembly;
- a first collar member fixedly attached to said body member;
- a second collar member longitudinally slidably mounted about said body member, said second collar member being constructed of highly conductive material and slidable within the magnetic flux field of one of said first and second electric coils;
- a plurality of borehole-engaging members bridgingly supported between said frist and second collar members;
- and
- circuit means for generating an electrical signal functionally related to the eddy current loading on said one coil in response to the movement of said second collar member within said magnetic flux field of said one coil, said signal being representative of the diameter of said borehole.
Apparatus for measuring the diameter of a borehole traversing subsurface earth formations, comprising:
- an elongated body member adapted to traverse a borehole, said body member including a non-ferromagnetic portion;
- an electrical coil assembly mounted within said non-ferromagnetic portion of said body member, said coil assembly including first and second electrical coils wound on a core;
- an oscillator circuit for simultaneously generating an alternating magnetic flux field about said first and second coils;
- a first collar member longitudinally and slidably fixed on said body member;
- a second collar member longitudinally slidable about said body member and said first electrical coil, said second collar member having a substantially uniform outer diameter portion and a tapered contour portion;
- a plurality of equispaced borehole-engaging members pivotally attached to and bridgingly supported between said first and second collar members;
- a spring biasing assembly for outwardly biasing said borehole-engaging members;
- and
- an electrical circuit coupled to said coil assembly for generating an electrical signal functionally related to the eddy current loading on said first coil in relation to said second coil, said loading resulting from the movement of said second collar member in relation to said first coil.
Dependencies are inferred from the claim text.