Detector
AssigneeSchlumberger Technology Corporation
InventorsGerald Meeten, Michael Paul Barrett
Life of this patent
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Abstract
A casing position locator for detecting structural features of a borehole casing, the locator including: a plurality of field generators for generating respective dynamic magnetic fields which combine to provide a dynamic test magnetic field to interact with the casing, where the test field includes a magnetic field null point located where the respective dynamic magnetic fields substantially cancel each other out; and a sensor for detecting a change in the position of the null point, relative to the sensor, due to the interaction.
Claims17
A method for determining structural features of a borehole casing, comprising:
- using a first field generator to generate a first dynamic magnetic field;
- using a second field generator to generate a second dynamic magnetic field;
- configuring the first and the second dynamic field generators such that the first and the second dynamic field generators produce a dynamic magnetic test field, wherein the test field includes a magnetic field null point where the first and the second dynamic magnetic fields substantially cancel each other out;
- passing the first and the second dynamic field generators through the borehole casing;
- and
- sensing at least one of a change in location of the null point or a change in magnetic field strength at the null point resulting from a change in permeability of the casing;
- using at least one of the sensed change in the location of the null point or the change in the magnetic field strength at the null point to detect changes in the permeability of the casing;
- and
- using the changes in the permeability to determine the structural features of the casing.
Dependencies are inferred from the claim text.