Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Well name: 759B

Leg: 122

Location: Exmouth Plateau (tropical SE Indian Ocean)

Latitude: 16¡ 57.25' S

Longitude: 115¡ 33.61' E

Logging date: July, 1988

Bottom felt: 2103 mbrf (used for depth shift to sea floor)

Total penetration: 28 mbsf

Total core recovered: none

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 ~66 mbsf.

Processing

Depth shift: Original logs have been depth shifted to the sea floor (- 2103 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 short spacing sonic logs have been processed to eliminate some of the noise and cycle skipping experienced during the recording. 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.

The results of acoustic processing are questionable, due to the poor quality of the original data; no processing has been performed in the 97.5-120 and 195-208 mbsf intervals were the original data was extremely degraded. Invalid sonic data were recorded in the 145-160 mbsf interval.

Invalid resistivity data were recorded in the 145-173 mbsf interval.

Data recorded through bottom-hole assembly, such as the gamma ray data above 66 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