Barbados - Rio de Janiero

January 13 - March 8, 2003

Personnel:

• Brice Rea, Logging Staff Scientist

Planned Tool Deployments

• Triple Combo
• FMS/Sonic
• MGT

LOGGING PLAN
Logging operations are scheduled to take place at all of the primary sites (DR-8B, DR-3C, DR-5B and DR-2). The two standard ODP tool string configurations will be deployed. The triple combination (triple combo) tool string logs formation resistivity, density, porosity, natural gamma ray, and borehole diameter, and will be run first, followed by the Formation MicroScanner (FMS)-Sonic tool string, which provides an oriented 360^o resistivity image of the borehole wall, logs of formation acoustic velocity, natural gamma ray, and borehole diameter. The Lamont-Doherty Earth Observatory (LDEO) high-resolution Multisensor Gamma Tool (MGT) will be deployed on the top of the triple combo tool string and run on a separate pass at all of the primary sites. In addition, the Well Seismic Tool (WST) is scheduled for use at primary Sites DR-2 and DR-8B. This tool will be used to undertake a checkshot survey, providing accurate traveltime data for calibrating the velocity logs.

The main aims of the leg are the recovery of Paleogene and Cretaceous fossiliferous oozes and chalks and Cretaceous black shales. Borehole logging will provide continuous in situ measured physical properties, which can be used to assess the physical, chemical, and structural characteristics of the formation. Even in the event of complete core recovery, the expansion of sediments resulting from elastic strain recovery requires core data to be depth-shifted (compressed), which can be accomplished by depth matching core multisensor-track (MST) data (density, porosity, and gamma ray) to equivalent log data using the Sagan core-log integration program. The situation is reversed when incomplete core recovery occurs. The recovery of black shale intervals may be problematic, but they should be clearly identifiable using the natural gamma, density, and porosity logs. The continuous logs of density, porosity, gamma ray, and resistivity are readily amenable to cyclostratigraphic analysis, which can identify the influence of orbital forcing on climate cycles evident in sedimentary deposits. Formation density and velocity profiles (derived by splicing core and log data) will be calibrated using the checkshot surveys and used to produce formation acoustic impedance profiles, depth/time models, and synthetic seismograms. The synthetic seismograms provide a direct link between the depth domain core data and the time domain seismic data, allowing the accurate location, dating, and interpretation of the reflectors seen in the regional seismic data.

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