Method for Locating Casing Downhole Using Offset XY Magnetometers

摘要

An apparatus, method and computer-readable medium for locating a joint of a casing disposed in a borehole are disclosed. The apparatus includes a sensor oriented in a plane orthogonal to a longitudinal axis of the casing. The sensor measures a magnetic field induced in the casing by the earth's magnetic field. A tool conveys the sensor through the casing along a path that is radially offset from a longitudinal axis of the casing. Transverse magnetic field measurements are obtained by the sensor at a plurality of depths along the casing. A change in the transverse measurements is identified and used to determine the location of the casing joint.

主权项

1. A method of locating a joint of a casing disposed in a borehole, comprising:
conveying a sensor through the casing along a path radially offset from a longitudinal axis of the casing, wherein the sensor is oriented in a plane orthogonal to the longitudinal axis of the casing; detecting by the sensor a change in a transverse component of an earth-induced magnetic field in the casing as the sensor is conveyed along the path; and locating the casing joint using the detected change in the transverse component.