| 摘要 |
A method for determining the orientation of the axis of a borehole with respect to an Earth-fixed reference coordinate system at a selected series of locations in the borehole, the borehole having a trajectory, and adapted to receive a drill string, comprising defining a model for the influence of magnetic interference from elements of the drill string on the measurement of components of the Earth's magnetic field in the borehole in terms of an unknown vector, a measurement vector, and a measurement matrix relating the unknown vector and the measurement vector; measuring at two or more selected locations along the borehole trajectory: 1) at least one of: i) two cross-borehole components of the Earth's gravity field at the selected locations in the borehole, and ii) two cross-borehole components and an along-borehole component of the Earth's gravity field at the selected locations in the borehole; 2) two cross-bore hole components of the Earth's magnetic field and an along-borehole component of the Earth's magnetic field at the selected locations; computing the elements of the measurement vector and the measurement matrix from the measured Earth's gravity and Earth's magnetic field components for the selected locations; solving for the unknown vector using the measurement vector And the measurement matrix; computing for each of the selected locations corrected values for the Earth's magnetic field components using the unknown vector, the model, and the measured Earth's magnetic field components; and determining a value for the azimuthal orientation of the borehole axis at each the selected locations using the corrected values for the Earth magnetic field components and the measured gravity components.
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