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US 4,491,796 AGranted
Borehole fracture detection using magnetic powder
AssigneeShell Oil Company
InventorDan G. Smith
Life of this patent
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Abstract
A method for detecting fractures in a formation penetrated by a borehole wherein the fracture is first filled with a magnetic material and the formation then logged with an instrument that responds to the earth's magnetic field. The fracture can be filled with a magnetic material by including it in the drilling mud when the well is drilled and changing the mud system before logging. The logging tool can comprise a simple compass or a magnetometer.
Claims6
A method for locating a fractured formation penetrated by a borehole comprising:
- removing the mudcake from the wall of the borehole;
- introducing a magnetic powder in the range of 5 to 10 microns into the borehole so as to penetrate the fracture;
- removing all magnetic material from the borehole;
- and
- logging the borehole with an instrument that is responsive to the earth's magnetic field to detect any distortions in the earth's normal magnetic field caused by the magnetic powder in the fracture.
2 more elements
Dependencies are inferred from the claim text.