Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Hole: 1199A

Leg: 194

Location: Marion Plateau (tropical SW Pacific Ocean)

Latitude: 20°58.692' S

Longitude: 152°54.947' E

Logging date: February 21-22, 2001

Bottom felt: 327 mbrf

Total penetration: 419.5 mbsf

Total core recovered: 92.2 m (22 %)

Logging Runs

Logging string 1: DIT/HLDS/APS/HNGS (one pass)

Logging string 2: FMS/GPIT/NGT/LSS (one pass)

The DIT/HLDS/APS/HNGS went to the bottom of the hole and data were excellent except for two wide sections near the top of the hole. Hole conditions had degraded for the FMS/GPIT/NGT/LSS run; it reached only 129 mbsf even after a wiper trip.

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/HLDS/APS/HNGS: Bottom-hole assembly at 70 mbsf

Processing

Depth shift: The original logs were depth matched to the HSGR log from the DIT/HLDS/APS/HNGS run. The logs were then shifted to the sea floor (-326 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 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 processing: The travel time logs from SDT tool 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, eight 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 original data only covered a 35m section, and was very noisy. However, good velocities were obtained for the majority of this interval. The number of reasonable measurements at each depth (#POINTS) is a measure of the confidence of the velocity determination: 8 is best and 0 or 1 are very uncertain. The derived velocities should be used with 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 1199A was in gauge for most of the bottom section, but was wider than 18" between 118-130 and 155-219 mbsf.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP Leg 194 IR volume. For further questions about the logs, please contact:

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