ODP logging contractor: LDEO-BRG

Hole: 1224F

Leg: 200

Location: Hawaii-2 Observatory (central tropical N Pacific)

Latitude: 27° 53.3634' N

Longitude: 141° 58.7567' W

Logging date: 20-21 January 2002

Bottom felt: 4978 mbrf (used to shift to sea floor)

Total penetration: 174.5 mbsf

Total core recovered: 37.7 m (25.7%)

Logging Runs

Logging string 1: DIT/HLDT/APS/HNGS

Logging string 2: FMS/DSI/GPIT/NGT (3 passes)

No major problems were encountered while logging Hole 1224F, and good quality logs were recorded. A third logging string (the WST3, for a checkshot survey) was attempted but had to be abandoned because the tool telemetry was working only intermittently, and the airgun and hydrophone were also experiencing problems. The wireline heave compensator was used to counter ship heave.

Bottom-hole Assembly

The following bottom-hole assembly/pipe depths are as they appear on the logs after differential depth shift (see "Depth shift" section) and depth shift to the sea floor. As such, there might be a discrepancy with the original depths given by the drillers onboard. Possible reasons for depth discrepancies are ship heave, use of wireline heave compensator, and drill string and/or wireline stretch.

DIT/HLDT/APS/HNGS: Bottom hole assembly at ~ 35 mbsf.

FMS/DSI/GPIT/NGT: Bottom hole assembly at ~ 33 mbsf.

Processing

Depth shift: The original logs were depth matched to the HSGR from the DIT/HLDT/APS/HNGS run and were then shifted to the sea floor (-4978 m). The sea floor depth could not be determined from the step in gamma ray values at the sediment-water interface, because the signal was too weak. Therefore the "bottom felt" depth given by the drillers (see above) was used as the logging sea-floor depth.

Depth matching is typically done in the following way. One log is chosen as reference (base) log (usually the total gamma ray log from the run with the greatest vertical extent), and then the features in the equivalent logs from the other runs are matched to it in turn. This matching is performed automatically, and the result checked and adjusted as necessary. The depth adjustments that were required to bring the match log in line with the base log are then applied to all the other logs from the same tool string.

Gamma-ray processing: NGT data have been processed to correct for borehole size and type of drilling fluid. The HNGS data were corrected for hole size during the recording.

Acoustic data: The DSI tool was operated in the following modes. Pass 1, P&S and lower dipole; Pass 2, cross dipole; Pass 3, P&S, upper dipole, and Stoneley mode. The data from Pass 1 and 3 are of fair quality: the rough hole and fractured basalt made for difficult acoustic logging conditions. For the cross dipole mode (Pass 2), waveforms were recorded but the shear wave velocities will only be determined after post-cruise work.

High-resolution data: Bulk density and neutron porosity data were recorded at a sampling rate of 2.54 and 5.08 cm, respectively. The enhanced bulk density curve is the result of Schlumberger enhanced processing technique performed on the MAXIS system onboard. While in normal processing short-spacing data is smoothed to match the long-spacing one, in enhanced processing this is reversed. In a situation where there is good contact between the HLDT pad and the borehole wall (low-density correction) the results are improved, because the short spacing has better vertical resolution.

Quality Control

Null value=-999.25. This value may replace recorded log values or results that are considered invalid (ex. processed sonic data).

During the processing, quality control of the data is mainly performed by inter-comparison of all logging data. Large (>12") and/or irregular borehole affects most recordings, particularly those that require eccentralization (APS, HLDT) and a good contact with the borehole wall. Hole deviation can also affect the data negatively; the FMS, for example, is not designed to be run in holes deviated more than 10 degrees, as the tool weight might cause the caliper to close.

Data recorded through bottom-hole assembly should be used qualitatively only because of the attenuation on the incoming signal.

Among the resistivity logs, the deep and spherically focused logs provide better measurement than the medium resistivity, which often presents spikes and does not correlate well with any other log.

Hole diameter was recorded by the hydraulic caliper on the HLDT tool (CALI) and on the FMS string (C1 and C2). Above 102 mbsf the hole is about 12 inches in diameter with only a few thin wider intervals; below this depth, the hole is rougher and wider, reaching 17 inches at 148-150 mbsf. The FMS caliper arms do not appear to have fully opened; the measurement made does not match the hole diameter as given by the HLDT caliper log.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP Leg 200 IR volume. For further questions about the logs, please contact:

Trevor Williams
Phone: 845-365-8626
Fax: 845-365-3182
E-mail: Trevor Williams

Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia