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Center for Deep Earth Exploration (CDEX)

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Site Survey

A site survey is a review, carried out before drilling begins, of the proposed drill site to assess the safety of drilling operations. All available past survey reports and geological data, either from this site, or from nearby sites, are reviewed as part of this safety assessment. Seafloor bathymetry and water depths are examined for suitable drilling locations and sea floor hazards. Piston cores acquired from the drill site are used for geotechnical analysis to evaluate formation strength for supporting the heavy BOP (Blow Out Preventer) on the seafloor. Multi-channel seismic reflection surveys are used to assess potential geological and drilling hazards such as fractures and possible gas reserves. Past review and future prediction of weather and sea current records are used to assess operational risks.

  • Survey purpose Survey methods
    Collect geological data Collect past survey reports and geological data.
    Seafloor map Multi narrow beam acoustic surveywindow produces a seafloor map from acoustic reflection waves.
    Formation strength of the seafloor Piston core sampleswindow used to measure the strength of the seafloor formation.
    Geohazard Multi-channel seismic reflection surveywindow which are used to interpret subsurface geology.
    Weather and metocean (Records of wind speed, typhoon, wave height, etc) Collect past records of weather and metocean data.
    Sea current Collect past records of sea currents. Survey with mooring system and analyze data. Sea currents are measured during the cruise with laser doppler anemometer by Chikyu and by supply boat.
  • A schematic overview of a typical mooring system. The mooring system is fixed by a weight to the sea floor. A buoy supports the sensors in the water column. After the survey is complete, the system is recovered by releasing the anchor (via acoustic signal). Mooring system survey data are available from JAMSTEC’s DARWIN data website

    A schematic overview of a typical mooring system. The mooring system is fixed by a weight to the sea floor. A buoy supports the sensors in the water column. After the survey is complete, the system is recovered by releasing the anchor (via acoustic signal).

Mooring system survey data are available from JAMSTEC’s DARWIN data website

JAMSTEC’s DARWIN data websitewindow

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