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doi:10.14379/iodp.sp.356.2014

Downhole measurements strategy

Formation temperature measurements

While APC coring in Hole A, a series of formation temperature measurements using the advanced piston coring temperature tool (APCT-3) are planned. If deemed necessary, the Sediment Temperature Tool may be deployed for additional temperature measurements.

Core orientation

All APC cores will be oriented with the FlexIT tool and will use nonmagnetic core barrels as much as possible.

Downhole wireline logging

At the time of writing this Scientific Prospectus, the contract for providing wireline logging services is not yet in place, but anticipated usage of basic wireline logging tools is similar to those provided during the Integrated Ocean Drilling Program. Wireline logging is currently planned for the deepest hole at each of our primary sites (Hole C or D), but implementation will actually depend on hole conditions. The wireline logging plan aims to provide information on in situ formation properties (lithologies, structures, and petrophysics) and orbital-scale cyclicities.

Three standard IODP tool string configurations will be deployed: the triple combination (triple combo), Formation MicroScanner (FMS)-sonic, and Versatile Seismic Imager (VSI).

At each site, the first tool string deployed will be the triple combo, which measures density, neutron porosity, resistivity, and natural and spectral gamma ray, along with calipers. The caliper log provided by the density tool will allow an assessment of hole conditions and the potential for success of subsequent logging runs. The second run will be the FMS-sonic and will record gamma ray, sonic velocity (for compressional and shear waves), and high-resolution electrical images. The compressional velocity logs will be combined with the density logs to generate synthetic seismograms for detailed seismic-log correlations. To calibrate the integration of well and seismic data, the third run in each hole will be a vertical seismic profile (VSP) recorded with the VSI, which requires the use of a seismic sound source. The expected spacing between stations is 25 m over the entire open interval of each hole logged. Spacing could be adjusted for specific targets or hole conditions. The seismic sound source used during the VSP survey will be subject to the IODP marine mammal policy, including daylight-only operation of the sound source, and may have to be postponed or canceled if certain policy conditions are not met. For more information on specific logging tools, please refer to iodp.ldeo.columbia.edu/TOOLS_LABS/.

Downhole measurements will be the only data available where core recovery is incomplete. Moreover, the data will provide common measurements for core-log integration (density, natural gamma radiation, and magnetic susceptibility) and establish the link between borehole and core features and reflectors on seismic profiles by synthetic seismograms and VSP.

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