Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Well name: 747C

Leg: 120

Location: Kerguelen Plateau (central S Indian Ocean)

Latitude: 54° 48.68' S

Longitude: 76° 47.64' E

Logging date: March, 1988

Bottom felt: 1705.7 mbrf (used for depth shift to sea floor)

Total penetration: 350.5 mbsf

Total core recovered: 49.5 m (34 %)

Logging Runs

Logging string 1: DIT/SDT/NGT

Wireline heave compensator was not used to counter ship heave; heave was about 20 ft.

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/SDT/NGT: Bottom-hole assembly at ~108 mbsf.

Processing

Depth shift: Because only one run was recorded, no differential depth shift was required. The original logs have been depth shifted to the sea floor (- 1705.7 m).

Gamma-ray processing: NGT data have been processed by Schlumberger to correct for borehole size and type of drilling fluid.

Acoustic data processing: The array sonic tool was operated in standard depth-derived borehole compensated mode, including long-spacing (8-10-10-12') and short-spacing (3-5-5-7') logs. Because of the extremely noisy character of the sonic logs, processing was performed by Schlumberger.

Quality Control

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

During the processing, quality control of the data is mainly performed by cross-correlation of all logging data. The processed acoustic data show little or no correlation with the other data and therefore should be used with caution.

The focused resistivity log was affected by frequent spikes and is not included in the database.

Hole diameter was recorded by the 3-arm mechanical caliper device (MCD).

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 120. For further questions about the logs, please contact:

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