Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Hole: 1219A

Leg: 199

Location: Paleogene Equatorial Transect (Equatorial E Pacific Ocean)

Latitude: 7° 48.009' N

Longitude: 142° 0.9390' W

Logging date: 25-26 November, 2001

Bottom felt: 5074 mbrf (logger's sea floor = 5073.5 mbrf)

Total penetration: 250.8 mbsf

Total core recovered: 241.1 m (96.1 %)

Logging Runs

Logging string 1: DIT/HLDT/APS/HNGS/MGT (4 passes, MGT only on pass 3 and 4)

Logging string 2: FMSDSI/GPIT/NGT (2 passes)

No major problems were encountered while logging Hole 1219A. The wireline heave compensator was used to counter ship heave.

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: Bottom hole assembly at ~ 83 mbsf (pass 1).

FMS/DSI/GPIT/NGT: Bottom hole assembly at ~ 83 mbsf.

Processing

Depth shift: The original logs were depth matched to the HSGR from DIT/HLDT/APS/HNGS pass 1 and were then shifted to the sea floor (-5073.5 m). The sea floor depth was determined by identifying the step in gamma ray values at the sediment-water interface. The logging sea-floor depth differs 0.5 m from the "bottom felt" depth given by the drillers (see above).

Depth matching is typically done in the following way. One log is chosen as reference (base) log (usually the total gamma ray log from the run with the greatest vertical extent), and then the features in the equivalent logs from the other runs are matched to it in turn. This matching is performed automatically, and the result checked and adjusted as necessary. The depth adjustments that were required to bring the match log in line with the base log are then applied to all the other logs from the same tool string. In Hole 1219A, the gamma radiation values are quite low (<20 API unitsq), and common features are not always easy to identify in all passes. For the two FMS/DSI/GPIT/NGT passes, the caliper logs were used for depth matching, because they gave clearer results than the gamma logs and were more likely to lead to well-matched FMS images.

Gamma-ray processing: NGT data have been processed to correct for borehole size and type of drilling fluid. The HNGS data were corrected for hole size during the recording.

Acoustic data: The DSI tool was operated in three modes for both passes: P&S mode (medium frequency for pass 1, high frequency for pass 2), dipole mode (upper dipole for pass 1, lower dipole for pass 2), and FMD (first motion detection) mode. The P&S mode compressional wave velocities are valid in only a few places. The dipole mode gave shear wave velocities in about 10% of the hole. The FMD mode essentially replicates the functioning of the LSS (long-spaced sonic logging tool), and the compressional wave results are generally good for the whole hole: the two passes yield similar logs, and both show features observed in other porosity-sensitive logs. The FMD compressional and dipole shear results are presented in the data files. Both the original travel time data and the edited velocity data (derived from the travel time data) are included.

High-resolution data: Bulk density and neutron porosity data were recorded 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 has better vertical resolution.

Quality Control

Null value=-999.25. This value generally replaces invalid log values or results.

During the processing, quality control of the data is mainly performed by inter-comparison 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). The hole size was near bit size in the lowermost 20 m of the hole and between 145 and 195 mbsf. Elsewhere the hole is wider, reaching beyond the maximum extent of the HLDT caliper arm (18 inches) between 209 and 223 mbsf. The hole is rough between 85 and 115 mbsf.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP Leg 199 IR volume. For further questions about the logs, please contact:

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