Use of magneto-resistive sensors for borehole logging
AssigneeBaker Hughes Incorporated
InventorHelmut Lechen
Life of this patent
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Abstract
A downhole caliper instrument utilizing a linear or arcuate magneto resistive sensor to determine the position of one or more caliper arms which extend from a carrier tool to touch the surface of a borehole wall. A processor and firmware are included to calculate and plot the borehole radius. A plurality of magneto resistive sensors are provided to calculate the sine, cosine and tangent for accurate motion of each independent arm. The magneto resistive sensors sense the position a precise magnetic ruler linked to the caliper arm. The position of the caliper arm determines the radius of the borehole. Calculation of Radius/Diameter is preferably performed in the computer on surface. The downhole controller's firmware controls the multiplexer switching, A/D conversion and other functions.
Claims20
A caliper instrument for calculating the radii and diameter of a bore hole comprising:
- an instrument body having at least one arm pivotably attached to the body for contacting the surface of the bore hole wall;
- a magnetic ruler linked to the arm;
- and
- a magneto resistive sensor for sensing the position of the magnetic ruler for determining the position of the arm.
A method for calculating the diameter of a bore hole comprising:
- for contacting the surface of the bore hole wall with an instrument body having at least one arm attached to a body;
- sensing a magneto resistive sensor signal to determine the position of a magnetic ruler for determining the position of the arm;
- and
- calculating a diameter of the borehole, from the signal .
Dependencies are inferred from the claim text.