| 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 (g &cir& NOt ) measurements and determination of azimuth angle psi from magnetic field (B &cir& NOt ) measurements, the determinations being carried out in conventional XYZ-and-NEV coordinate systems coupled by Euler-angle coordinate transformations. In particular g &cir& NOt and B &cir& NOt are measured at least at two borehole depths such that phi i NOTEQUAL phi i+1, psi i and psi i+1 being calculated from B &cir& NOt i = [ phi i]<T> [ theta i]<T>{[ psi i]<T>B &cir& NOt e} + B &cir& NOt p and sin<2> psi i + cos<2> psi i = sin<2> psi i+1 + cos<2> psi i+1, with i as number of measurement, B &cir& NOt e as local earth magnetic field, and B &cir& NOt p 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. |
