Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG
Hole: 1171D
Leg: 189
Location: South Tasman Rise (Tasman Sea)
Latitude: 48° 29.9975' S
Longitude: 149° 6.7222' E
Logging date: April, 2000
Bottom felt: 2159 mbrf
Total penetration: 958.8 mbsf
Total core recovered: 525.40 m (73.9 %)

Logging Runs

Logging string 1: DIT/APS/HLDS/HNGS

The DIT/APS/HLDS/HNGS tool string reached the bottom of the hole without problem, and recorded good logs. A malfunction of the head tension gauge on the GHMT tool string as it was being lowered down the hole, combined with the tool string landing on a bridge, caused the logging cable to over-spool and kink. The kinked cable had to be cut. On lowering the pipe to clear the bridge, the end of pipe deviated from the borehole and became plugged. Significant over pull was required to remove the pipe, and logging operations at Hole 1171D were terminated.

Bottom-hole Assembly

The following bottom-hole assembly 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 and drill string and/or wireline stretch.

DIT/APS/HLDS/HNGS: Bottom-hole assembly at 151 mbsf

Processing

Depth shift: The original logs were shifted to the sea floor (-2159 m). The sea floor depth is determined by the step in gamma ray values at the sediment-water interface. It coincides with the "bottom felt" depth given by the drillers (see above).

Gamma-ray processing: The HNGS data were corrected for hole size during the recording.

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 HLDS 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 invalid log values or results.

Large (>12") and/or irregular borehole affects most recordings, particularly those that require eccentralization (APS, HLDS) and a good contact with the borehole wall. In general, Hole 1171D was fairly smooth, with borehole diameter ranging from 11 to 14 inches. Above 250 m, the hole is washed out beyond the maximum extent of the caliper arm (19 inches).

The SFLU resistivity log contains anomalous spikes from 298 and 307 mbsf.

The wireline heave compensator stopped at certain intervals during logging, because of excessive ship heave. Depth control is degraded in these intervals (813-840, 851-881, 916-934 mbsf)

Data recorded through bottom-hole assembly, such as the gamma ray data, should be used qualitatively only because of the attenuation on the incoming signal.

Hole diameter was recorded by the hydraulic caliper on the HLDS tool (LCAL).

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 189. For further questions about the logs, please contact:

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