Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Hole: 1243B

Leg: 203

Location: Equatorial Pacific Ion (equatorial NE Pacific)

Latitude: 5° 18.0543' N

Longitude: 110° 4.2544' W

Logging date: June 24-25, 2002

Water depth: 3868 mbrf (used for depth shift to sea floor)

Total penetration: 195.3 mbsf

Total core recovered: 26.17 m (30.19 %)

Logging Runs

Logging string 1: DIT/APS/HLDS/HNGS (main and repeat)

Logging string 2: FMS/GPIT/DSI/SGT (2 passes)

Logging string 2: WST (basement section only)

The TAP tool was included in the DIT/APS/HLDS/HNGS tool string but the data could not be downloaded.

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/APS/HLDT/HNGS: Bottom-hole assembly at ~ 82 mbsf (main pass)

FMS/DSI/GPIT/SGT: Bottom-hole assembly at ~82 mbsf (both passes).

Processing

Depth shift: The DIT/APS/HLDS/HNGS repeat pass was depth matched to the DIT/APS/HLDS/HNGS main run using the SFLU log. The ECGR log from the FMS/GPIT/DSI/SGT pass 1 was depth matched to the HSGR log from the DIT/APS/HLDS/HNGS main run, with some cross-checking with the caliper logs. The match between gamma ray logs is not always clear, particularly near the base of the hole. The ECGR log from FMS/GPIT/DSI/SGT pass 2 was matched to the shifted ECGR log from pass 1. All logs were then shifted to the sea floor (-3868 m). The sea floor depth is usually determined by the step in gamma ray values at the sediment-water interface, but in this case there is no clear step in gamma ray values, so the driller's mudline depth (3868 mbrf) was used.

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.

Environmental corrections: The HNGS and SGT data were corrected for hole size during the recording. The APS and HLDS have been corrected for standoff and hole diameter respectively during the recording.

Acoustic data processing: The dipole shear sonic imager (DSI) was operated in three modes: P&S monopole (both passes), high frequency upper dipole (both passes), and lower frequency lower dipole (pass 1). The lower dipole data has not been included in the online database because of its poor quality. The data from the upper dipole and monopole modes is of slightly better quality. First motion detection mode was also attempted but could not collect any usable data.

High-resolution data: Bulk density and neutron porosity data were recorded at a sampling rate of 2.54 and 5.08 cm, respectively. SGT gamma ray data were sampled every 5.08 cm. 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 HLDS 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 may replace invalid log values or results.

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, HLDS) 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 HLDS tool (LCAL) and on the FMS string (C1 and C2). The hole is mostly in gauge below 114.5 mbsf, and wider than the caliper maximum above 114.5 mbsf: the log data is excellent below 114.5 mbsf.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 203. For further questions about the logs, please contact:

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