Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Well name: 763B

Leg: 122

Location: Exmouth Plateau (tropical SE Indian Ocean)

Latitude: 20¡ 35.19' S

Longitude: 112¡ 12.52' E

Logging date: August, 1988

Bottom felt: 1378.9 mbrf (used for depth shift to sea floor)

Total penetration: 653.5 mbsf

Total core recovered: 376.36 m (81 %)

Logging Runs

Logging string 1: DIT/SDT/NGT

There are no information in the logging report from this hole about use of wireline heave compensator to counter ship heave.

Bottom-hole Assembly

The following bottom-hole assembly depth is as it appears on the logs after 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/SDT/NGT: Bottom-hole assembly at ~375.5 mbsf

Processing

Depth shift: Original logs have been depth shifted to the sea floor (- 1378.9 m).

Gamma-ray processing: NGT data have been processed 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. The data are of very poor quality, as the tool failed to pick the acoustic signal in most of the hole. Only the data The long spacing data recorded in the 374-386, 476--529, and 553-570 mbsf intervals have been processed in an attempt to improve the quality of the logs. Using two sets of the four transit time measurements and proper depth justification, four independent measurements over a -2ft interval centered on the depth of interest are determined, each based on the difference between a pair of transmitters and receivers. The program discards any transit time that is negative or falls outside a range of meaningful values selected by the processor.

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. With the exception of acoustic data, the logs recorded are generally good.

Data recorded through bottom-hole assembly, such as the gamma ray data above 198 mbsf, should be used qualitatively only because of the attenuation on the incoming signal.

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

Additional information about the logs can be found in the ÒExplanatory NotesÓ and Site Chapter, ODP IR volume 122. For further questions about the logs, please contact:

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