Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Hole: 1189B

Leg: 193

Location: Manus Basin (Bismarck Sea)

Latitude: 3° 43.236' S

Longitude: 151° 40.506' E

Logging date: December 25-26, 2000

Bottom felt: 1693 mbrf

Total penetration: 206 mbsf

Total core recovered: 13.7 m (7.8 %)

Logging Runs

Logging string 1: HTGC (one main and one repeat pass)

Logging string 2: DIT/HLDS/APS/HNGS/HTGC (main and repeat pass)

Logging string3: FMS/GPIT/NGT/DSI/HTGC (2 passes)

The HTGC was run first to measure the borehole fluid temperature in order to prevent subsequent tool strings from being cooked by temperatures outside their tolerance range. The maximum temperature was about 45 °C on the first run.

The wireline heave compensator was used to counter ship heave.

Bottom-hole Assembly-Casing

The following bottom-hole assembly and 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.

HTGC (main pass): Bottom-hole assembly at 26 mbsf

DIT/HLDS/APS/HNGS/HTGC (main pass): Bottom-hole assembly at 26 mbsf

FMS/GPIT/NGT/DSI/HTGC (pass 1): Bottom-hole assembly at 26 mbsf.

FMS/GPIT/NGT/DSI/HTGC (pass 2): recorded open-hole.

Casing at 34 mbsf.

Processing

Depth shift: The original logs were depth matched to the HSGR log from the main pass of the DIT/HLDS/APS/HNGS/HTGC run. The logs were then shifted to the sea floor (-1692 m). The sea floor depth is determined by the step in gamma ray values at the sediment-water interface. It differs by 1 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.

Gamma ray processing: NGT data from FMS/GPIT/NGT/DSI/HTGC Pass 2 have been processed to correct for borehole size and type of drilling fluid. No processing could be performed on Pass 1 due to repeated crashes of the GeoFrame module used in the processing. The HNGS data were corrected for hole size during the recording. The HTGC gamma ray was not corrected for borehole size.

Acoustic data processing: The DSI was run in P&S, Stoneley, and Crossed Dipole modes for the first run, and in P&S, Stoneley, and Lower Dipole low frequency modes for the second run. The P&S and Stoneley wave velocities were derived using a slowness time coherence technique on the recorded waveforms. This was done in near-real time during the logging operation on the Schlumberger MCM unit. The data from this hole are often invalid and should therefore be used only with extreme caution.

DIT data: The SFLU log contains anomalous spikes, due to a tool malfunction.

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 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 generally replaces recorded log values or results which are considered invalid.

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). Hole 1189B was between 10 and 14.5 inches wide for most of the logged interval.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP Leg 193 IR volume. For further questions about the logs, please contact:

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