Dynamic borehole azimuth measurements

摘要

A method for making dynamic borehole azimuth measurements while drilling includes processing cross-axial magnetic field measurements in combination with accelerometer measurements to compute the dynamic borehole azimuth. In one or more embodiments, the cross-axial magnetic field measurements and the accelerometer measurements may be used to compute the magnitude of a cross-axial magnetic field component, a toolface offset, and a borehole inclination, which may in turn be used to compute the dynamic borehole azimuth. The disclosed methods may utilize near-bit sensor measurements obtained while drilling, thereby enabling a near-bit dynamic borehole azimuth to be computed while drilling.

主权项

1. A method for making a dynamic borehole azimuth measurement while rotating a downhole measurement tool in a borehole, the method comprising:
(a) rotating a downhole tool in the borehole, the downhole tool including a cross-axial magnetic field sensor and an axial accelerometer; (b) obtaining a set of cross-axial magnetic field measurements and a set of axial accelerometer measurements while the downhole tool is rotating in (a); (c) processing the set of cross-axial magnetic field measurements obtained in(b) to compute a magnitude of a cross-axial magnetic field component; and (d) processing the magnitude of the cross axial magnetic field component computed in (c) and the set of axial accelerometer measurements obtained in (b) to compute the dynamic borehole azimuth, wherein the dynamic borehole azimuth is computed in (d) according to the following equation:cos⁢⁢Azi=B2-Bxy2B-AzG⁢sin⁢⁢Dsin⁡[arccos⁡(AzD)]⁢cos⁢⁢D wherein Azi represents the dynamic borehole azimuth, Bxy represents the magnitude of the cross-axial magnetic field component computed in (c), Az represents an axial accelerometer measurement, G represents the magnitude of the earth's local gravitational field, B represents the magnitude of the earth's local magnetic field, and D represents the local magnetic dip angle.