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doi:10.2204/iodp.proc.310.103.2007

Methods¹

Expedition 310 Scientists²

Introduction

This chapter documents the primary procedures and methods employed by various operational and scientific groups during the offshore and onshore phases of Integrated Ocean Drilling Program (IODP) Expedition 310. This information concerns only shipboard and Onshore Science Party methods described in the site chapters. Methods for postcruise research conducted on Expedition 310 samples and data will be described in individual scientific contributions to be published after the Onshore Science Party. Detailed drilling and engineering operations are described in the “Operations” sections in the individual site chapters.

Shipboard scientific procedures

Numbering of sites, holes, cores, and samples

Expedition numbers for IODP expeditions are sequential, starting with 301. Drilling sites are numbered consecutively, and for a European Consortium for Ocean Research Drilling (ECORD) Science Operator (ESO)–operated platform, numbering starts with Site M0001 (the “M” indicates the ESO-operated mission-specific platform). For Expedition 310, the first site was Site M0005. Multiple holes may be drilled at a single site. For all IODP drill sites, a letter suffix distinguishes each hole drilled at one site. The first hole drilled is assigned the site number with the suffix “A,” the second hole takes the site number and the suffix “B,” and so forth.

The cored interval is measured in meters below seafloor. Depth below seafloor is determined by subtracting the initial drill pipe measurement to seafloor from the total drill pipe measurement. For Expedition 310, the cored interval normally consisted of the entire drilled section, but in some cases the upper interval was drilled without coring.

If necessary, recovered core is split into sections with a maximum length of 1.5 m and numbered sequentially from the top, starting at 1 (Fig. F1). By convention, material recovered from the core catcher of a sedimentary core is treated as a separate section labeled “CC” (core catcher) and placed below the last section recovered in the liner. The core catcher is assigned to the top of the cored interval if no other material is recovered.

When recovered core is shorter than the cored interval, the top of the core, by convention, is equated to the top of the cored interval to achieve consistency in reporting depth-in-core. Any sample removed from a core is designated by distance measured in centimeters from the top of the section to the top and bottom of the sample removed. A full identification number for a sample consists of the following information: expedition, site, hole, core number, core type, section number, piece number (for hard rock), and interval in centimeters measured from the top of section. For example, a sample identification of “310-M0005A-3R-3, 80–85 cm,” represents a sample removed from the interval 80–85 cm below the top of Section 3, Core 3R (“R” designates that this core was taken using the rotary core barrel [RCB]), from Hole M0005A during Expedition 310 (Fig. F1).

All IODP core identifiers indicate core type. For Expedition 310, the following abbreviations are used:

• R = RCB, and
• M = hammer sample.

Core handling during the offshore phase of Expedition 310

As soon as a core was retrieved on deck, it went through a sequence of processing steps. The core catcher was given to the sedimentologists and coral specialists for description. With the exception of interstitial water (IW) and microbiology, no sampling of the core catchers was undertaken during Expedition 310. Next, the core was marked into section lengths by the curator, each section was labeled, and the core was cut into sections. Samples for IW (using rhizon syringes) and microbiological (by using a spatula through a small window cut in the liner) analyses were taken. Each section was sealed at the top and bottom by attaching color-coded plastic caps: blue to identify the top of a section and clear at the bottom. A yellow cap was placed on section ends where a whole-round sample was removed, and the sample code was written on the yellow cap. Caps were usually secured to liners by coating the liner ends and inside rims of caps with acetone before attaching the caps. Core section liners were permanently labeled with an engraving tool. The length of the core in each section and the core catcher sample were measured to the nearest centimeter; this information was logged into the Offshore Drilling Information System (OffshoreDIS).

No core splitting took place during the offshore phase of Expedition 310. Whole cores were saturated with seawater prior to running through the multisensor core logger (MSCL). Cores that contained unlithified sediments were not saturated. After the MSCL, lithological and sedimentological observations through plastic liners were carried out. Cores were then drained before being stored in the refrigeration container.

Core handling procedures changed partway through Expedition 310, during coring of Hole M0015B: it was decided to use split steel liners instead of regular plastic liners. Cores had to be removed from the steel liner for curation and were carefully transferred into plastic liners by splitting one side of the liner, wedging it open, and sliding the cored material inside. After sealing the split side of the liner with heavy-duty tape, cores were curated and handled as normal.

Core handling during the Expedition 310 Onshore Science Party

After being taken out of refrigerated storage, cores were split lengthwise into working and archive halves. Sections containing significant lengths of massive coral were treated slightly differently (see “Specialist sampling of massive Porites”). Harder cores were split with a diamond saw. Softer cores, less common in this expedition, were split with a wire or saw, depending on the degree of induration. Wire-cut cores are split from bottom to top, so investigators should be aware that older material could have been dragged up the core on the split face of each section.

Archive halves were described visually. Thin sections were made from specific samples when requested by the scientists. Digital images of archive halves were made with a digital imaging system followed by discrete color reflectance measurements. Archive halves were then photographed using a color digital camera. Close-up color photographs were taken of particular features for illustrations in the summary of each site, as requested by individual scientists.

The working half of the core was sampled for both the Onshore Science Party and postcruise studies. Each sample was logged into OffshoreDIS by location and by the name of the investigator receiving the sample. The IODP curator and database maintain information about all samples taken. Samples are sealed in plastic vials, cubes, or bags, labeled, and stored as appropriate. Samples were routinely taken for Onshore Science Party physical property studies, which are described below.

Following initial Onshore Science Party measurements and sampling, both halves of the cores were shrink-wrapped in plastic to prevent rock pieces from vibrating out of sequence during transit. Both halves were then placed in labeled plastic D-tubes, sealed, and transferred to refrigerated storage at the Bremen Core Repository.

Operations equipment

Drilling platform

Water depths at the drill sites ranged from 41.65 to 117.54 m and required the use of a mission-specific platform. The DP Hunter, a dynamically positioned (DP) vessel with a large moonpool, was contracted as the drilling vessel (Fig. F2). The drilling contractor was Seacore of Gweek, Cornwall (UK), who installed a drilling rig on the DP Hunter over the moonpool and onto part of the aft deck. The DP Hunter is a Class 2 DP vessel, and as such has a minimum dual redundancy in propulsion and navigation systems that met IODP and international environmental requirements for the coring operation.

Coring system

From the outset, it was determined by the Operations Superintendent that the coring tools used during Expedition 310 should be of mining type, suitably prepared and installed to operate from a heaving vessel holding station using DP. This decision was based on the previous operational experiences of coring coral formations at Enewetak in the Marshall Islands and on the Great Barrier Reef in Australia and from stationkeeping using DP while coring in various water depths worldwide.

Seacore was contracted to carry out all drilling operations. They installed and operated their R100 rig, previously constructed for IODP Expedition 302, together with a Wirth mining-style rig suitably adapted for offshore and piggyback coring (where the mining coring rig is installed on top of the conventional R100 rig) (Fig. F3). An American Petroleum Institute (API) drill string set by the R100 was used as the conductor pipe for all operations. A drilling and reentry template (DART), constructed for earlier works in high tidal regimes, was deployed on the API pipe as the seabed connector and reaction force for the secondary drill string (Fig. F4).

Drilling and reentry template

The DART is a heavy circular template with a hollow internal section and cutting teeth on the basal circumference to allow the DART to be drilled into the seabed for stability (Fig. F4). The DART is attached to the API drill string to form a connection between the vessel and the seabed that can be held in tension to allow a mining drill string to pass through it and core the formations below. Two different configurations of the DART were used. The first was with three legs sitting on the seabed, but this proved to be too unstable. The second, more stable, configuration was with a short stinger fitted through the DART and attached to the API pipe. The whole assembly was then drilled ~1 m into the seabed. This effectively leveled the DART and allowed it to lock into the seabed.

Drill string/Conductor pipe

A 5 inch API drill string with 4½ inch internal flush tool joints was used between the DART and the R100 top drive. This was deployed conventionally and used to drill the DART into the seabed in all but the first borehole (see “Drilling and reentry template”). The drill string was tensioned between the DART and the top drive, under compensated conditions, to stabilize the conductor pipe into which the coring string was run. Approximately 8 T of pullback was held in compensation, allowing 8 T of reaction force for the coring rig. Heave conditions were variable from 0.5 to 3.5 m stroke on the compensator.

Coring tools

A standard Longyear HQ3 3 m long core barrel assembly was used. This comprised an outer core barrel and a wireline interchangeable inner assembly fitted with a plastic liner. This was run on HRQHP drill pipe set in stands of two for running pipe.

The coring bits used with the system were all standard HQ3 pattern with a 96 mm outer diameter and 62 mm inner diameter. A corresponding reaming shell was also fitted to the outer core barrel above the bit. A selection of natural, synthetic, and impregnated diamond bits was carried to allow for optimum coring in any formation. Core was initially collected in an industry-standard HQ3 polyvinylchloride (PVC) liner tube, which served as the triple tube of the HQ3 system. However, because of the nature of the coral formation, this plastic liner was often crushed or torn and contributed to early bit blocking. After discussion with the expedition scientists, a traditional stainless steel or chromed steel split liner insert was trialed. The trials were successful, with demonstrable improvements in core recovery, core quality, and rates of penetration. The split liner insert was used for the rest of the expedition.

A hammer sampler was made up from a spare HQ overshot assembly to allow attempts to be made to clear the bit while coring and to remove bridges while logging. Normally, such a tool is always carried for geotechnical operations, and its successful use during the expedition suggests it is a useful and versatile tool and should be carried at all times, whatever suite of coring equipment is being deployed.

Incorporated into the landing/​latching assembly of the inner core barrel was a ball valve that had to be pressurized and then released to indicate that a positive latch had been made between the outer and inner core barrels. This system worked well and dramatically reduced mislatching problems associated with wireline operations.

Combinations of bits and catchers were used to maximize core recovery as the expedition progressed and more knowledge was gained about the lithologies being cored. Impregnated diamond bits of medium to medium-hard matrix were used together with a corresponding reaming shell.

Combination basket/​core spring catchers were used in the top-hole sections, core springs with a small finger set of catchers were used in friable formations, and conventional core springs were used in competent formations. In all cases, a clear PVC liner or a split steel liner was used to collect the core, but core was always curated and stored in a plastic liner. Two core barrel assemblies were set up for running to minimize changeover time during trips. Variable-length liners and spacers were used to keep from wasting plastic liner if it was used in short core runs.

For open-hole drilling, where there was a danger of bit blocking, a full-face insert bit was carried, allowing retention of the coring facility further downhole. This technique was used on a number of occasions and worked effectively.

Wireline retrieval was by means of a standard Longyear HQ overshot deployed by wire from a hydraulic wireline winch. An overshot release sleeve system was also carried for “dry hole” emplacement of the core barrels.

Downhole logging tools

Downhole logging services were contracted and managed by the European Petrophysics Consortium (EPC). Details and results of the expedition logging program are given in “Downhole logging” and in the “Downhole logging” sections in the individual site chapters.

Through-pipe underwater video camera

The IODP Environmental and Pollution Safety Panel (EPSP) specified that ESO should have a facility to inspect the seabed before and after coring to ascertain that minimal damage would be done to any living coral present at the drill site. In addition, EPSP also allowed a “clearance zone” with a 150 m radius for drilling around each proposed site (which was increased to 350 m around proposed Site TAH-02A 4) so that patches of living coral could be avoided while drilling proceeded.

The British Geological Survey (BGS) provided an underwater color video camera system and manufactured a deployment frame to allow it to work inside the drill pipe. It is based on diver helmet–operated systems. The system worked well, and good video coverage was obtained from a number of sites. Importantly, the video demonstrated that it is possible to drill in a reef setting with minimal disturbance to the environment. Additionally, the camera was used for pipe and seabed slope examination when there were technical issues associated with deployment at a particular site. A similar camera system was carried by Seacore as a backup. The Seacore cable was used until an issue with the resistance of the ESO cable was resolved.

The camera could be further developed to provide scale, direction, and possibly an angled view. Assuming that proper site surveys have been conducted, this is a more cost effective tool to carry than a remotely operated vehicle (ROV), which requires more expenditure, additional organization, and an infrastructure (including deck space) to meet the same objective.

Echo sounder

It became obvious partway through the expedition that site survey information was not detailed enough and was often misleading. Various attempts were made by the Co-Chief and Staff Scientists to obtain both further data and the parameters surrounding collection of the previous data. Much of this was forthcoming and allowed laybacks of seismic lines to be calculated and better images to be made of the bathymetry from additional raw data.

However, even after additional refinements, the mapped bathymetry did not agree with manual spot checks (using the tautwire and lead line) at many sites, especially on the shelf edge. With the help of the Co-Chief Scientists, a high-resolution shallow-water echo sounder was located onshore and purchased by the Operations Superintendent for the expedition. A transducer pole was made up on board from which to deploy the transducer in the moonpool. After some trials to obtain the best settings, the echo sounder was used systematically across survey grids, and the data collected allowed suitable drilling sites to be located.

Data handling, database structure, and access

Data management during offshore and onshore phases of Expedition 310 had two overlapping stages. The first stage was the capture of metadata and data during the expedition (offshore and onshore). Central to this was OffshoreDIS, which stored drilling information, core curation information, and primary measurement data. The second stage was the longer term postexpedition archiving of Expedition 310 data sets, core material, and samples. This function was performed by the World Data Center for Marine Environmental Sciences (WDC-MARE) and the Bremen Core Repository (BCR).

Offshore drilling information system

OffshoreDIS is a flexible and scalable drilling information system, originally developed for the International Continental Drilling Program (ICDP). The underlying data model for OffshoreDIS is compatible with Janus, the BCR, PANGAEA, and the Lac-Core in Minneapolis (Minnesota, USA). For the specific expedition platform configuration and offshore and onshore workflow requirements of Expedition 310, the OffshoreDIS data model, data pumps, and user interfaces were adapted. Offshore, the system was used to capture basic information related to core and sample curation, core photographs, and section and sample label printing. In addition, the database also stored primary data measurements. These included

• Geophysical downhole logging data (from the EPC management office, carried out by University of Montpellier II, ISTEEM),
• MSCL data,
• Visual core descriptions (VCDs) of core sections (in liner) and core catchers,
• IW analysis, and
• Microbiological data.

Also, scientists produced a variety of spreadsheet files, text documents, and graphics containing data, descriptions, and interpretations in different formats. Therefore, in addition to OffshoreDIS, all data files were stored in a structured file system on a shared hard drive. A specific Web interface for OffshoreDIS (XDIS) was used to distribute OffshoreDIS content via an intranet to all networked computers.

Expedition 310 data were then transferred to the information system of WDC-MARE during the second phase. WDC-MARE was founded in 2000 and is a member of the International Council of Scientific Unions World Data Center system. PANGAEA is the geoscience information system used by WDC-MARE. It has a flexible data model that reflects the information processing steps in the earth science fields and can handle any related analytical data (Diepenbroek et al., 1999, 2002). It is used for processing, long-term storage, and publication of georeferenced data related to earth sciences. Essential services supplied by WDC-MARE/​PANGAEA are project data management and distribution of visualization and analysis software. Data management functions include quality checking, data publication, and metadata dissemination that follows international standards. Data captured by OffshoreDIS were transferred to this long-term archive following initial validation procedures as soon as they became available; data transfer was completed by the time of publication of this volume. Until the end of the moratorium period, the data were not public and access was restricted to the expedition scientists. However, following the moratorium, the data were published on the Internet (www.wdc-mare.org), and WDC-MARE will continue to acquire, archive, and publish new results derived from Expedition 310 samples and data sets.

Hardware installation

OffshoreDIS was implemented in SQLServer-2000 with Microsoft-based client PCs connecting to the system through a Microsoft Access–like user interface. For the offshore phase of the expedition, OffshoreDIS was installed on a server on the DP Hunter. A second server was used as a hot-standby and data backup system. Incremental backups and full backups were made regularly, along with additional tape backups. These backups comprise OffshoreDIS and the shared file server.

Core, section, and sample curation using OffshoreDIS

Expedition 310 followed IODP procedures and naming conventions in core, section, and sample handling (see “Shipboard scientific procedures”). OffshoreDIS handled data curation and printed the appropriate labels also to IODP standards. The curation data comprise

• Expedition information,
• Site information (latitude, longitude, water depth, start date, and end date),
• Hole information (hole naming by a letter, latitude, longitude, water depth, start date, and end date),
• Core data (core number, core type, top depth, bottom depth, number of sections, core catcher availability, curator, core on deck, date and time, and additional remarks),
• Section data (section number, section length, curated length, curated top depth of section, section length, and curated length),
• Sample information (repository, request, request part, code observer, expedition, site, hole, core, section, half, sample top, sample bottom, and sample volume),
• Calculated core recovery percentage on the basis of the drilled or cored length and the curated recovery, and
• Calculated section recovery on the basis of the section length and the curated length.

No correction was made in cases where the recovery exceeded 100%. Top and bottom depth of the section (in meters below seafloor) was calculated from core-top depth. The section and sample label formats follow the standard Ocean Drilling Program (ODP)/IODP convention. They include barcodes of the section/​sample code and the complete section/​sample code (Expedition-Site-Hole-Core-Core type-Section-Half-Interval and sample request code). This standardization guarantees data exchange among the repositories and enables information flow between the implementing organizations.

¹Expedition 310 Scientists, 2007. Methods. In Camoin, G.F., Iryu, Y., McInroy, D.B., and the Expedition 310 Scientists. Proc. IODP, 310: Washington, DC (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/​iodp.proc.310.103.2007

²Expedition 310 Scientists’ addresses.

Publication: 4 March 2007
MS 310-103

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