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doi:10.14379/iodp.sp.354.2014 Risks and contingencyWe consider that unconsolidated sediments (rapidly accumulating silt and sand, etc.) could create unstable borehole conditions that negatively impact core recovery/quality and may prevent reaching our depth objectives. If this occurs at our deep penetration site (MBF-3A), we have the possibility of deploying a reentry cone and casing to stabilize the upper part of the hole, thereby enhancing our ability to recover deeper cores and logs. However, this would take an additional ~1 week of time. In addition, if this occurs at any of the other sites (MBF-6A, MBF-5A, MBF-4A, and MBF-1A), we might have to switch to RCB coring to reach the depth objectives—this would require an additional trip of the drill string. As neither of these operations are included in the current time estimate, other planned operations would therefore have to be reduced or eliminated. If unconsolidated sands cause problems in APC core recovery and/or quality, we might choose to deploy the half-length APC system. We may also do this to extend high-quality piston cores to deeper depths. This will result in increased wireline times and is not currently in our time estimate; other planned operations would therefore have to be reduced or eliminated. |
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