| 摘要 |
<p>A method for determining the azimuth angle of a borehole being drilled, whilst a drillstring is rotating about the axis of the borehole, by means of an instrument which is carried by the drillstring down the borehole, and which is rotating with the drillstring, comprising the steps of:- … … (a) sensing on a plurality of occasions during a cycle of rotation of the drillstring the instantaneous components of the gravitational field in the direction of the drillstring axis and in a direction perpendicular thereto; … (b) sensing on a plurality of occasions during a cycle of rotation of the drillstring the instantaneous components of the magnetic field in the direction of the drillstring axis and in a direction perpendicular thereto; … (c) determining the time average of the gravitational component in the direction of the drillstring axis; … (d) determining the time average of the magnetic field component in the direction of the drillstring axis; … (e) determining the real and imaginary parts of the discrete fourier transform of said gravitational field component in a direction perpendicular to the drillstring axis as a function of time; … (f) determining the real and imaginary parts of the discrete fourier transform of said magnetic field component in a direction perpendicular to the drillstring axis as a function of time; and … (g) determining the azimuth angle from said time averaged gravitational component and said time associated magnetic field component in the direction of the drillstring axis, and from said real and imaginary associated with said gravitational field component in a direction perpendicular to the drillstring axis and with said magnetic field component in a direction perpendicular to the drillstring axis. … </p> |
