Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Hole: 504B

Leg: 148

Location: Costa Rica Rift (tropical NE Pacific Ocean)

Latitude: 1° 13.611' N

Longitude: 83° 43.818' E

Logging date: March, 1993

Water depth (from Leg 111): 3474 mbrf

Total penetration: 2111 mbsf

Total core recovered: 9.58 m (8.7 %), 2000-2111 mbsf interval

Logging Runs

Logging string 1: DLL/SDT (3 sections)

Logging string 2: FMS/GPIT/NGT (5 passes)

Logging string 3: WST

Wireline heave compensator was used to counter ship heave resulting from the mild/rough sea conditions.

Casing

The following 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.

DLL/SDT: Casing at ~ 275 mbsf

FMS/GPIT/NGT: Casing at ~ 275 mbsf.

Processing

Depth shift: Original logs have been interactively depth shifted with reference to the shallow laterolog (LLS) from Leg 140 and to the sea floor (- 3474 m). Only the upper part (952.5-3221.5 mbsf) of the FMS/GPIT/NGT could be depth shifted with reference to the GPIT data from leg 140. The NGT was not used for depth correlation because of its very low signature and lack of good repeatability.

A list of the amount of differential depth shifts applied at this hole is available upon request.

Gamma-ray processing: NGT data from FMS/GPIT/NGT run have been processed to correct for borehole size and type of drilling fluid. No NGT data was recorded in the 982-996, 1093-1100, and 1833-1884 mbsf intervals.

Acoustic data processing: The array sonic tool was operated in standard depth-derived borehole compensated mode, including long-spacing (8-10-10-12') logs. The 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. The data has been spliced at 1419.7 and 1300 mbsf.

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 (ex. processed sonic data).

During the processing, quality control of the data is mainly performed by cross-correlation of all logging data. Hole 504B data are generally of very good quality.

Hole diameter was recorded by the 3-arm caliper on the DLL/SDT string and by the caliper on the FMS string (C1 and C2).

The resistivity data has been spliced at 1310 and 1450 mbsf.

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