Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Well name: 767B

Leg: 124

Location: Celebes Basin (Celebes Sea)

Latitude: 4° 47.49' N

Longitude: 123° 30.30' E

Logging date: November, 1988

Bottom felt: 4916 mbrf

Total penetration: 739 mbsf

Total core recovered: 585 m (79 %)

Logging Runs

Logging string 1: DIT/SDT/NGT

Logging string 2: ACT/GST/NGT

No information available could be found about use of wireline heave compensator to counter ship heave.

Bottom-hole Assembly/Drill Pipe

The following bottom-hole assembly and drill pipe 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 and drill string and/or wireline stretch.

DIT/SDT/NGT: Bottom-hole assembly at ~106 mbsf

DIT/SDT/NGT: Drill pipe at ~50 mbsf

ACT/GST/NGT: Bottom-hole assembly at ~ 106 mbsf

ACT/GST/NGT: Bottom-hole assembly at ~ 80 mbsf.

Processing

Depth shift: Original logs have been interactively depth shifted with reference to NGT from ACT/GST/NGT run and to the sea floor (- 4915 m). This value corresponds to the water depth as seen on the logs and differs 1 meter from the "bottom felt" depth (see above) given by the drillers. The program used is an interactive, graphical depth-match program, which allows to visually correlate logs and to define appropriate shifts. The reference and match channels are displayed on the screen, with vectors connecting old (reference curve) and new (match curve) shift depths. The total gamma ray curve (SGR) from the NGT tool run on each logging string is used to correlate the logging runs most often. In general, the reference curve is chosen on the basis of constant, low cable tension and high cable speed (tools run at faster speeds are less likely to stick and are less susceptible to data degradation caused by ship heave). Other factors, however, such as the length of the logged interval, the presence of drill pipe, and the statistical quality of the collected data (better statistics is obtained at lower logging speeds) are also considered in the selection. A list of the amount of differential depth shifts applied at this hole is available upon request.

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

Acoustic data processing: The SDTlogs 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.

Geochemical data: Due to technical problems, no geochemical data from this hole could be migrated into the online database. The results of the processing, however, can be viewed in the paper by Pratson, E. et al. (1991), Data Report: geochemical; results from wireline logs in the Celebes Sea, Sites 767 and 770 of Leg 124. In Silver, E. A., Rangin, C., von Breymann, M. T. et al., Proc. ODP, Sci. Results, 124: College Station, TX (Ocean Drilling Program): 541-552.

Quality Control

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

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 3-arm mechanical caliper device.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 124. For further questions about the logs, please contact:

Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia