A new approach, loading a logging source down through the center of a measurement-while-drilling (MWD) collar, offers features that address both radiation safety and environmental issues. This technique reduces crew exposure, allows for safe and timely procedures on the rig floor, and enables fishing of the sources should the bottomhole assembly (BHA) have to be abandoned. After the sources are fished, actions to recover the BHA, abandon the BHA or sidetrack the well are not restricted by the presence of these logging sources.

The new source handling approach includes:

  • - A fishable dual source assembly.

    The gamma ray source and the neutron source are mechanically linked together. This permits them to be simultaneously loaded, unloaded or fished if the BHA becomes stuck.

  • - An integrated collar/shield design.

    The dual source assembly is loaded directly through its transport shield into the drill collar. At no time is the source unshielded on the rig floor. This reduces the total source loading time and minimizes crew exposure, resulting in a safe and timely operation.

  • - Auxiliary safety equipment.

    In the event that a source cannot be unloaded after the job is finished, collar shields are clamped into place for safe handling and transport of the collar.

  • - Source security and integrity.

    The risk of erosion due to mud flow against the source receptacle is quantified. Tests conducted show no erosion problems at rated flow rates with up to 3% fracture sand by volume in the mud.

The system has been tested extensively in the laboratory and in the field for both fishability and erosion resistance, and has proven to an efficient and reliable approach.

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