Geometrical instruments – Indicator of direction of force traversing natural media – Borehole direction or inclination
Patent
1987-01-20
1989-04-11
Martin, Jr., William D.
Geometrical instruments
Indicator of direction of force traversing natural media
Borehole direction or inclination
33313, E21B 47022
Patent
active
048193364
ABSTRACT:
For the purposes of determining the orientation of a surveying instrument in a borehole, while compensating for the effects of perturbing magnetic fields associated with magnetized sections of the drill string both above and below the instrument, the inclination angle .theta. and the highside angle .phi. of the instrument are determined, together with two transverse components Bx and By of the local magnetic field as measured at the instrument in the borehole. Additionally either a single component of, or the magnetide of, the true earth's magnetic field at the location of the borehole is ascertained from a look-up table or directly by measurement away from the influence of the drill string. A value .PSI.a for the azimuth angle of the instrument is then determined from the inclination and highside angles, the measured component(s) of the local magnetic field, and only the single component of, or the magnitude of, the true earth's magnetic field.
REFERENCES:
patent: 3935642 (1976-02-01), Russell
patent: 4163324 (1979-08-01), Russell et al.
patent: 4510696 (1985-04-01), Roesler
Martin, Jr. William D.
NL Sperry-Sun, Inc.
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