Operational strategy

IODP Expedition 347 will be implemented as a Mission Specific Platform (MSP) expedition, where the platform and coring services are contracted from the industry market and scientific services are provided by ESO. At the time of writing, the tendering exercise for platform and coring services was in progress. Therefore, many operational details such as the drilling platform, coring rig, coring methodology, logging tools, measurements plan, and core workflow will not be available until the contract for the primary infrastructure is in place.

The latest platform, facilities, coring strategy, measurements plan, scheduling, and port call information will be updated on the ESO Expedition 347 web page (​expeditions/​347/​347.php).

Drilling platform

Because of the range in water depths at the proposed sites (23–451 m), the drilling platform is likely to be a dynamically positioned geotechnical vessel equipped with piston and rotary coring tools. The chosen platform will have sufficient capacity by way of food and accommodation for 24 h operation.

Coring rig and coring methodology

Details of the coring rig and coring methodology will be published on the ESO Expedition 347 web page once the vessel and coring contractors have been selected (​expeditions/​347/​347.php).

It is planned that, during coring of the microbiology boreholes, a perfluorocarbon tracer and/or microspheres will be continuously injected into the drill fluid for contamination testing.

Coring strategy

It is planned to core at least two boreholes at each primary site for the paleoceanographic objectives. These will be supplemented by as many as five short cores that will capture an undisturbed record of the water/sediment interface and the upper 0.75 m of the sedimentary sequence. Additionally, a microbiology-dedicated borehole will be cored at four microbiology sites in order to recover a useful volume of material for microbiological analyses. Please consult the ESO Expedition 347 web page for up-to-date coring strategy details (​expeditions/​347/​347.php).

Core on deck

Once the drilling operation commences and core begins to arrive on deck, after initial labeling of cores, the operations team will be responsible for delivering the cores to the curation container. The operation will proceed using a changeover of inner core barrels to ensure continuity of the coring operation in as timely a fashion as possible. The deck operators will deploy an empty core barrel immediately after the previous one has been retrieved, and then address core removal and subsequent readying of that core barrel for reuse. As the cores will be collected in plastic liners, the usual IODP curation procedures will be followed (​en/​Offshore_core_curation_and_measurements.html). After curation, core materials are passed to the Science Party members for onboard description, analysis, and sampling as described in “Science operations,” below.

Downhole logging

During all MSP expeditions, the downhole logging program is integrated with the scientific objectives to ensure maximum scientific output. This may include the use of specialist third-party tools.

To facilitate downhole measurements and core petrophysics for MSPs, the European Petrophysics Consortium (EPC) has been developing protocols for use both offshore and in collaboration with the Center for Marine Environmental Sciences (MARUM) team during the Onshore Science Party.

Unlike the R/V Chikyu and riserless vessels where the pipe size is constant and allows a standard set of logging tools to be deployed, MSPs have variable pipe sizes and drill in a variety of water depths, each of which provides constraints on the anatomy of logging operations. Pipe diameter is the controlling factor, and it is envisaged that a wide range, from slimline memory-mode tools to standard oil-field tool suites, may be utilized. Water depth is also an important constraint because some MSP expeditions will operate in very shallow territorial waters where the deployment of nuclear sources may be prohibited or severely restricted.

Logging services will be contracted as part of the services for IODP Expedition 347 and will be managed by the EPC. The logging equipment and team will be constructed to allow for a seamless operation on the platform, ready to undertake any requirements as the project progresses.

Because the choice of logging tools depends on the platform and coring tool set up, details of the wireline logging program will be published on the ESO Expedition 347 web page once the vessel and coring contractors have been selected.