Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Hole: 1198B

Leg: 194

Location: Marion Plateau (tropical SW Pacific Ocean)

Latitude: 20°57.930' S

Longitude: 152°44.005' E

Logging date: February 10, 2001

Bottom felt: 330.5 mbrf

Total penetration: 522.6 mbsf

Total core recovered: 116.6 m (35.7 %)

Logging Runs

Logging string 1: DIT/HLDS/APS/HNGS (one pass)

The DIT/HLDS/APS/HNGS reached only 234.5 mbsf before being stopped by an obstruction at the same place the drill had become stuck while drilling the hole.

The wireline heave compensator was used to counter ship heave.

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, use of wireline heave compensator, and drill string and/or wireline stretch.

DIT/HLDS/APS/HNGS: Bottom-hole assembly at 74 mbsf.

Processing

Depth shift: The logs were shifted to the sea floor (-331.5 m). The sea floor depth is determined by the step in gamma ray values at the sediment-water interface. It differs by 1 m from 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 generally replaces recorded log values or results which are considered invalid.

Large (>12") and/or irregular borehole affects most recordings, particularly those that require eccentralization (APS, HLDS) and a good contact with the borehole wall.

Data recorded through bottom-hole assembly 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). Hole 1198B was wider than 18" between 100-192 mbsf and narrower than the bit-size below that.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP Leg 194 IR volume. For further questions about the logs, please contact:

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