Schlumberger Technology Corporation

Edouard Marienbach

Peter D Wraight

Jean-Michel Hache

Erik Rhein-Knudsen

Mike Evans

A measurement while drilling nuclear tool adapted to be coupled in the drill string to make formation evaluations and methods of using are described. A neutron source is positioned on the cylindrical axis of the tool while a connected gamma ray source is eccentered against an interior side of the cylindrical tool. Both sources can be axially removed from the tool along its interior. Novel source-detector configurations are provided in order to accommodate the constraints of the MWD environment. Gamma ray transparent windows are provided through both the drill collar and an external fluid excluder (stabilizer) at the positions of the gamma ray source and scintillator detectors. Neutron detectors may be of two different types at the same spacing from the source. Corrections are made for microphonic noise that arises while drilling and for natural gamma ray background. A drilling fluid density determination is made and is utilized to compensate for 'borehole' or 'standoff' effects.

Method and apparatus for subsurface formation evaluation

A borehole logging apparatus for performing radiation based measurements has a tubular body for movement through a borehole. The tubular body includes an upwardly opening passage and an interior chamber for accommodating the positioning and lengthwise insertion and removal of an energy radiating source. The radiation source includes an uppermost portion which may be remotely engaged by a source removing device for its removal in the event the tool becomes stuck in the borehole and in order to facilitate source handling at the earth's surface.

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Houston, TX, United States of America

Edouard Marienbach