| 摘要 |
<p>An electromagnetic method and apparatus for determining the azimuthal orientation of a drill bit instrumentation sub (70), with respect to a borehole bottom drilling assembly (150) includes an electromagnet (152) fastened to the drilling assembly to produce an auxiliary alternating electromagnetic field (162) having an axis (163) that is perpendicular to the borehole axis (160). The direction of the field lines (162) generated by this magnet (152) and the simultaneous measurement of an electromagnetic field (36) generated by current flow in a blowout well casing is measured by electromagnetic field sensors in the drill bit instrument sub (70) to determine the direction to a blowout The direction of the auxiliary field (162) produced by the electromagnet (152) makes it possible to determine the direction to the blowout with reference to the direction of drilling without using an intermediate parameter such as, for example, the direction of gravity.</p> |
