| 摘要 |
A method for determining the direction of a borehole during drilling comprises determination of inclination angle .theta. and highside angle .PHI. from gravity acceleration (?) measurements and determination of azimuth angle ? from magnetic field (B) measurements, the determinations being carried out in conventional XYZ-and-NEV coordinate systems coupled by Euler-angle coordinate transformations. In particular ? and B are measured at least at two borehole depths such that .PHI.i ? .PHI.i+1, ?i and ?i+1 being calculated from Bi = ¢.PHI.i!T ¢.theta.i!T{¢?i!TBe} + Bp and sin2?i + cos2?i= sin2?i+1 + cos2?i+1, with i as number of measurement, Be as local earth magnetic field, and Bp as perturbating magnetic field. As a result perturbating magnetic fields, for example caused by hot spots or nearby magnetic steel components in the drilling or logging string nearby the B-measuring device, are determined accurately.
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