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doi:10.2204/iodp.sp.335.2010

Risks and contingencies

Operational risks

The following operational risks were identified at the precruise meeting, based on past experience at ODP Holes 504B, 735B, and 1256D:

  1. The hole is not accessible because of formation collapse and cannot be cleaned to the bottom of the hole.

  2. Drilling equipment failure in the hole.

  3. Wireline tools stuck in the hole.

  4. Hole rectification operations that require specialist tools, equipment, or personnel not available during Expedition 335.

Weather-related risks are negligible and essentially avoided. Site 1256 has a 12 month weather window, and previous cruises to the site have not been affected by adverse conditions.

Risk responses

The above listed operational risks must be accepted and dealt with as they occur. The probability of the risks can be reduced to some degree by good operational practices. One of the reasons for success in Hole 1256D has been a prudent approach to operations, and to date there have been relatively few drilling equipment failures compared with other igneous crust holes. Aggressive drilling tactics have not been employed to increase penetration at the cost of core recovery. An appropriate suite of pre- and postcoring wireline operations have been conducted so that maximum scientific information has been gained at this important legacy site. We will continue with this philosophy and attempt to both deepen Hole 1256D and keep the hole intact for future drilling. The drilling operations team, led by Ron Grout, will ensure that Expedition 335 will sail with the best possible arsenal of fishing tools (fishing jars and intensifiers) to recover or mill out drilling or logging equipment potentially lost in the hole. However, situations may arise that are impossible to anticipate and plan for.

The success of Expedition 335 will be judged based on the added depth of penetration in Hole 1256D and the rate of core recovery. The scientific ocean drilling community has invested significant time and resources to establish and drill Hole 1256D to 1507 mbsf. Hence, the stabilization and remediation of this important legacy hole will be the primary objective should we encounter operational difficulties. Expedition 335 will take as much time as is available to explore all approaches for cleaning and/or stabilizing Hole 1256D until there is agreement that available options are exhausted. We do not envisage that we could reach such a situation in <10 days.

We may conclude that further operations in the hole will jeopardize future attempts to resuscitate Hole 1256D. In that case, it would be prudent to wait for a return to Hole 1256D with an appropriate armory of hole cleaning/fishing tools and/or specialist personnel. Should this case arise, we will suspend cleaning/stabilization activities, complete science operations at the site (e.g., wireline logging), and then move on to our contingency program.

Contingency program

For the worst-case scenario, where operations in Hole 1256D must be abandoned for some reason, a contingency plan has been mandated by the Science Planning Committee (SPC) of the IODP Science Advisory Structure (SAS). The SPC instructions call for the JOIDES Resolution to transit to the Costa Rica Seismogenesis Project (CRISP) operational area and continue operations from where Expedition 334 left off (SPC Motion 0908-14; SPC Consensus 0908-16). The general scientific and operational objectives of the CRISP program can be found in the Expedition 334 Scientific Prospectus (Vannucchi et al., 2010). The detailed coring and/or logging activities for a potential contingency operation cannot be anticipated until Expedition 334 is concluded.

In case the contingency plan is executed, the following rules and protocols apply:

  1. The priorities for CRISP contingency operations, to be finalized at a joint meeting of Co-Chief Scientists and Expedition Project Managers (EPMs) in port after Expedition 334, should favor coring of basement intervals in order to take advantage of the Expedition 335 scientific staff expertise. Expedition 335 will not include any sedimentologists or paleontologists.

  2. Expedition 335 Superfast scientists will become Expedition 334 CRISP shipboard science party members by virtue of recovering cores and executing basic shipboard measurements. However, they will not incur any obligation to conduct postcruise research and publish for Expedition 334 unless they explicitly choose to do so with a proposed research title (and associated sample request) no later than the last day of the cruise. Such proposals and sample requests must be in consideration of the existing CRISP proposed postcruise projects and collaborative in nature as appropriate according to general IODP practices.

  3. All CRISP science party members (i.e., those from Expeditions 334 and 335) will have moratorium access to Expedition 334 sample material. The postcruise moratorium is set no earlier than the end of Expedition 335. It could be delayed further if deemed necessary to allow all party members to adequately review and sample CRISP cores.

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