Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Hole: 1195B

Leg: 194

Location: Marion Plateau (tropical SW Pacific Ocean)

Latitude:  20°24.283' S

Longitude: 152°40.243' E

Logging date: January 29, 2001

Bottom felt: 430.8 mbrf

Total penetration: 520.44 mbsf

Total core recovered: 399.3 m (76.6 %)

Logging Runs

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

Logging string 2: WST (3 stations in the upper part of the hole)

After some problems getting out of the end of the pipe, the DIT/HLDS/APS/HNGS reached the bottom of the hole without further difficulty. The logging data are excellent. The MGT tool was present in the DIT/HLDS/APS/HNGS tool string, but did not collect data (it requires a separate pass of its own) because of concerns about hole deterioration and obtaining the higher priority WST data. Even after hole cleaning, the WST could not progress below 121 mbsf.

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 79.5 mbsf.

Processing

Depth shift: The logs were shifted to the sea floor (-430 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 1195B was less than 12" below 240 m and very smooth: excellent conditions for logging. Between 110 and 202 m the hole was wider than 18", apart from two sections where the hole had closed in (127-130 and 190-197mbsf).

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP Leg 194 IR volume.

For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.