Schlumberger Technology Corporation

Heather A Campbell

Guy P Vachon

Terry L Mayhugh

Marvin W Rasmussen

A method and apparatus for detecting magnetic marks on a wireline logging cable and for more accurately making depth measurements during logging is described. The method uses depth-based, rather than time-based, samples and calculations. A Hall Effect sensor samples the cable at regular depth intervals approximated by an encoder mechanism. The signal values from the Hall Effect sensor are signal processed to better discriminate the precise location of the magnetic marks on the cable. The location of the magnetic marks is used to refine the depth measurements from the encoder mechanism. Depth-based sampling eliminates detection dependence on cable speed, enhances detection ability, reduces computational load, and leads to more accurate determination of the location of magnetic marks.

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Cambridge, MA, United States of America

Heather A Campbell