Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Hole: 504B

Leg: 140

Location: Costa Rica Rift (tropical NE Pacific Ocean)

Latitude: 1° 13.611' N

Longitude: 83° 43.818' E

Logging date: November, 1991

Bottom felt: 3474 mbrf (used for depth shift to sea floor)

Total penetration: 2000.4 mbsf

Total core recovered: 47.7 m (12.6 %).

NOTE: Interval cored during Leg 140: 378.9 m

Logging Runs

Logging string 1: FMS/GPIT/NGT

Logging string 2: ACT/GST/NGT (3 passes)

Logging string 3: DLL/SDT

Wireline heave compensator was used to counter ship heave.

Bottom-hole Assembly/Casing

The following bottom-hole assembly/casing 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.

FMS/GPIT/NGT: Logged open-hole

ACT/GST/NGT: Logged open-hole

DLL/SDT: Bottom-hole assembly at ~275 mbsf. Casing shoe at 274 mbsf.

Processing

Depth shift: DLL/SDT logs have been interactively depth shifted with reference to DLL from Leg 111 and to the sea floor (- 3474 m). Because of the low gamma ray signature and the lack of repeatability between some of the runs, it has not been possible to depth-shift all the runs. The DLL from leg 111 has been used as reference for the depth shift of the lower and upper section of the DLL/SDT runs. Pass 2 of the ACT/GST/NGT run has been shifted with reference to the CSIG (capture cross section) curve from leg 111. Later, during the processing of the geochemical logs, it has been noted that there is a good correlation between the aluminum and the shallow laterolog (LLS), but the former is offset with respect to the laterolog. Therefore, the processed geochemical logs have been further shifted with reference to the shallow laterolog.

The upper part of the FMS/GPIT/NGT run has been shifted with reference to the SGR from Leg 111.

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.

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: Because of the extremely noisy character of the sonic logs, no processing has been performed.

Quality Control

null value=-999.25. This value generally appears in discrete core measurement files and also it may replace recorded log values or results which are considered invalid.

During the processing, quality control of the data is mainly performed by cross-correlation of all logging data. Large (>12") and/or irregular borehole affects most recordings. Hole deviation can also affect the data negatively; the FMS, for example, is not designed to be run in holes deviated more than 10 degrees, as the tool weight might cause the caliper to close.

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 caliper on the FMS string (C1 and C2).

During this leg GPIT data such as FX, FY, FZ and FNOR have been recorded in milli-amperes/meter instead of oersted. This explains the unusually large numbers present in the GPIT ascii files.

Additional information about the logs can be found in the ≥Explanatory Notes≤ and Site Chapter, ODP IR volume 140. For further questions about the logs, please contact:

Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia