An experimental pulsed-neutron logging-while-drilling (LWD) tool is currently under field test. The tool provides a suite of nuclear measurements that include neutron porosity, thermal neutron capture cross section (i.e. sigma), pulsedneutron density and the relative abundance of certain elements (e.g., calcium, silicon, iron, sulfur, etc) that are used to calculate mineralogy. The tool provides azimuthal measurements in real time that are useful for geosteering applications.

Use of a pulsed-neutron source eliminates the need for radioactive-chemical sources that are used in conventional nuclear LWD tools. This results in increased wellsite safety and efficiency. Procedures and equipment required for radioactive-source handling, storage and retrieval are also eliminated.

The experimental LWD tool is the result of a joint collaboration that began in 1995 between the Japan National Oil Corporation and Schlumberger. The primary goal of the tool is to demonstrate feasibility of pulsed-neutron measurements in the hostile LWD environment.

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