Wireline Standard Data Processing


ODP logging contractor: LDEO-BRG

Hole: 1022C

Leg: 167

Location: q California Margin (tropical NE Pacific)

Latitude: 40° 4.482' N

Longitude: 125° 20.558' W

Logging date: June, 196

Bottom felt: 1937.5 mbrf (used for depth shift to sea floor)

Total penetration: 387.7 mbsf

Total core recovered: 378.8 m (97.7 %)


Logging Runs


Logging string 1: DIT/HLDT/APS/HNGS (2 passes)

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

Logging string 3: GHMT/NGT (2 passes)


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


Bottom-hole Assembly


The following bottom-hole assembly 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.


DIT/HLDT/APS/HNGS: Recorded open-hole (pass 1)

DIT/HLDT/APS/HNGS: Bottom-hole assembly at ~52.5 mbsf (pass 2)

FMS/GPIT/SDT/NGT: Recorded open-hole (pass 1)

FMS/GPIT/SDT/NGT: Bottom-hole assembly at ~ 52.5 mbsf (pass 2)

GHMT/NGT: Recorded open-hole (pass 1)

GHMT/NGT: Bottom-hole assembly at ~ 52.5 mbsf (pass 2)




Depth shift: Original logs have been interactively depth shifted with reference to HNGS from DIT/HLDT/APS/HNGS pass 2, and to the sea floor (- 1937.5 m). 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 from the NGT and/or HNGS 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 and environmental corrections: Corrections for borehole size and type of drilling fluid were performed on the NGT data from the FMS/GPIT/SDT/NGT and GHMT/NGT tool strings. HNGS data from the DIT/HLDT/APS/HNGS tool string were corrected in real-time during the recording.


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. Because the original delay times from both passes are far higher than typical sea water values and are also affected by cycle skips, an attempt has been made using the best long-spacing set of transit times to eliminate some of the 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 results, however, are of very poor quality, because of the difficulty in editing the single transit times. The short-spacing configuration DTL (long-spacing delay time) from both pass 1 and 2, however, displays a decent correlation with the resistivity data and has been selected to derive the velocity profile at this hole. Because the velocity values are lower than the velocity of sea water, the data should be used qualitatively only.


High-resolution data: Bulk density and neutron porosity data were recorded with the HLDT and APS tools at a sampling rate of 2.54 and 5.08 cm respectively. The enhanced bulk density curve is the result of Schlumberger enhanced processing technique performed on the MAXIS system onboard. While in normal processing short-spacing data is smoothed to match the long-spacing one, in enhanced processing this is reversed. In a situation where there is good contact between the HLDT pad and the borehole wall (low density correction) the results are improved, because the short-spacing have better vertical resolution.


Geological Magnetic Tool: The Geological Magnetic Tool collected data at two different sampling rates, the standard 0.1524 m rate and 0.0508 m. Both data sets have been depth shifted to the reference run and to the sea floor. The total magnetic field measurement (MAGB) is invalid due to a technical problem during the recording.


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. Large (>12") and/or irregular borehole affects most recordings, particularly those that require eccentralization (APS, HLDT) and a good contact with the borehole wall. 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 hydraulic caliper on the HLDT tool (CALI) and on the FMS string (C1 and C2). No good caliper measurements were recorded during FMS pass 1.


Details of standard shore-based processing procedures are found in the "Explanatory Notes" chapter, ODP IR Volume 167. For further information about the logs, please contact:


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