Uncertainty Analysis Method for Intersecting Process of U-Shaped Horizontal Wells

Accurate monitoring and determination of the trajectory and relative position are two very important concerns during drilling the connection of two wells to form a U-shaped horizontal well. The composite error circle based on trajectory uncertainty analysis is introduced. The timing of using the magnetic ranging tool is established by comparing the diameter of the composite error circle with that of the ranging scope of the magnetic ranging tool. The profile is designed, and the key extension formula is given according to the characteristics of the magnetic ranging tool. The measurement principle of a Rotating Magnetic Ranging System, which is widely used during the drilling of U-shaped wells, is introduced in order to analyze the relative position uncertainty. Through analysis of the error sources, a covariance matrix of the relative position uncertainty is constructed, and its error ellipsoid and error ellipse are determined. The error ellipse is found to be beneficial in using the magnetic ranging tool during the drilling of U-shaped horizontal wells by comparing the semi-axis of the error ellipse and the radius of the borehole.

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