Magnetic logs are commonly used in wild-well kill operations to guide a relief well to a blowout well. Estimates of distance and direction to the blowout well are highly dependent on the assumed magnetic model of the blowout well casing. Theoretical and experimental results show that the magnetic poles of a long magnetized cylinder fit an exponentially distributed model rather than the standard impulsive-pole model. Magnetic techniques for determining range and direction from a relief well to a blowout well are explained, and modifications of these techniques based on the new magnetic model are developed. The techniques presented can be used during drilling operations with data from most measurement-while-drilling (MWD) tools. Substantial improvements in range estimates are achieved for near- and medium-range targets.
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