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Expedition 332 Scientists2


This chapter documents the methods associated with borehole observatory recovery and deployment during Integrated Ocean Drilling Program (IODP) Expedition 332: the SmartPlug recovery and GeniusPlug deployment in IODP Hole C0010A and the long-term borehole monitoring system (LTBMS) permanent observatory deployment in IODP Hole C0002G. In addition, a suite of logging-while-drilling (LWD) and measurement-while-drilling (MWD) downhole measurements were performed in Hole C0002G in order to identify the best positioning of the LTBMS borehole instruments. Some of those components (tiltmeter, seismometer, and strainmeter) were tested at several stages during LTBMS deployment to confirm the integrity of the instruments and cable connections.

Reference depths

Depths of each measurement are reported relative to both the drilling vessel rig floor (rotary table) and to the seafloor. These depths are determined by drill pipe and correlated by the use of distinct reference points. Depths are reported as LWD depth below seafloor (LSF), core depth below seafloor (CSF), drilling depth below rig floor (DRF) and meters below seafloor (mbsf) (IODP Depth Scales,​program-policies/).

Observatory deployment

Vortex-induced vibration (VIV) is a serious obstacle to deploying sensitive equipment by drill string through the Kuroshio Current, which can reach speeds of more than 5 kt across the entire Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) study area. The temporary and permanent observatories required a special design to resist VIV forces and protect the sensors and instruments, and modification of the drill string in certain sections (i.e., attachment of ropes) was also needed to reduce the effect of VIV forces.

Temporary observatory

A family of simple temporary borehole observatories was designed to be attached to a retrievable casing packer and provide rapid deployment and recovery. The SmartPlug is a temporary borehole observatory developed by the NanTroSEIZE Project Management Team Observatory Team that was installed during IODP Expedition 319 and recovered during this expedition. Onboard data were collected after download in the laboratory. The GeniusPlug is an upgraded version of the SmartPlug that includes a limited suite of biological experiments and geochemical sampling over time.

LTBMS observatory

The LTBMS observatory is an expansion of the circulation obviation retrofit kit (CORK) design developed to link to a seafloor observatory network, transmitting real-time data to a monitoring station on land. A series of systems checks were performed on the data and electrical cables running from the strainmeter, seismometer, and tiltmeter during LTBMS assembly and installation. The separate pressure sensor unit, a self-contained unit attached to the CORK head, was tested before being attached to the CORK head and again after cementing operations were completed. In total, the downhole sensors were checked nine times:

  1. After connection to the cables as the sensor carrier was run down,

  2. Before the cables were run through the swellable packer,

  3. After the cables were run through the swellable packer,

  4. Before the cables were cut prior to termination with the Ocean Design, Inc. (ODI) underwater mateable connectors (UMCs),

  5. After ODI termination was completed,

  6. After mounting ODI connectors on the CORK head,

  7. After the entire assembly was run into the water at ~350 m DRF,

  8. When the CORK head reached final depth before being run into the wellhead, and

  9. After the CORK was run into the borehole.

All tests were performed without encountering any problems.

1 Expedition 332 Scientists, 2011. Methods. In Kopf, A., Araki, E., Toczko, S., and the Expedition 332 Scientists, Proc. IODP, 332: Tokyo (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/​iodp.proc.332.102.2011

2Expedition 332 Scientists’ addresses.

Publication: 11 December 2011
MS 332-102