Use of magneto-resistive sensors for borehole logging
AssigneeBaker Hughes Incorporated
InventorHelmut Lechen
Life of this patent
Estimating the term…
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.
Claims16
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;
- a processor associated with the instrument body for calculating the radius of the borehole from the position of the arm;
- and
- first and second magneto resistive sensors associated with the instrument body for sensing the position of the magnetic ruler for determining the position of the arm, said first and second sensors located relative to each other to produce a first and second signal, respectively, wherein said first signal is shifted in phase 90° from said second signal for calculating the tangent of the sensed signals.
A method for calculating the diameter of a bore hole comprising:
- contacting the surface of the bore hole wall with an instrument body having at least one arm attached to the body;
- sensing magneto resistive sensor signals to determine the position of a magnetic ruler associated with the arm for determining the position of the arm;
- calculating a diameter of the borehole, from the signal;
- calculating the diameter of the bore hole from the position of the arm;
- and
- wherein the step of sensing the signals comprises sensing a signal from a first and a second magnetic pole sensor located 90° apart for calculating the tangent of the sensed signals.
Dependencies are inferred from the claim text.