Wireline Standard Data Processing


ODP logging contractor: LDEO-BRG

Hole: 1115C

Leg: 180

Location: Woodlark Basin (tropical SW Pacific Ocean)

Latitude: 9° 11.385' S

Longitude: 151° 34.42' E

Logging date: July, 1998

Water depth (as seen on logs): 1162.5

Total penetration: 802.5 mbsf

Total core recovered: 291.5 m (56 %)



Logging Runs


Logging string 1: DIT/APS/HLDS/HNGS

Logging string 2: FMS/SDT/GPIT/NGT (3 passes and downlog)

Logging string 3: UBI-GPIT/NGT (failed)

Logging string 4: WST

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/HLDS/HNGS: Bottom-hole assembly at ~79.5 mbsf

FMS/SDT/GPIT/NGT: Recorded open-hole (passes 1-2).

FMS/SDT/GPIT/NGT: Bottom-hole assembly at 79.5 mbsf (pass 3).




Depth shift: Original logs have been interactively depth shifted with reference to NGT from the FMS/SDT/GPIT/NGT runs and to the sea floor (- 1162.5 mbrf). This amount corresponds to the mudline as seen on the logs, which differs 2.2 from the "bottom felt" depth given by the drillers (see above). 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 (HSGR or SGR) from the HNGS or NGT 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 processing: NGT data from FMS/GPIT/SDT/NGT runs have been processed to correct for borehole size and type of drilling fluid. The HNGS data from DIT/HLDS/APS/HNGS was corrected for hole size during the recording.


Acoustic data processing: The array sonic tool was operated in linear array mode, with the 8-receiver array used in short and long spacing mode to provide full waveform analysis. Long-spacing (8-10-10-12') and short-spacing (3-5-5-7') data from pass 3 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, 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. Short and long-spacing data have been merged as follows:


top-450 mbsf: long spacing

450-537 mbsf: short spacing

537-575 mbsf: long spacing

575-600 mbsf: short spacing

600-616 mbsf: long spacing

616-640 mbsf: short spacing

640-bottom: long spacing


High-resolution data: Neutron porosity data were recorded at a sampling rate of 5.08 cm.


Quality Control


null value=-999.25. This may replace recorded log values or results that 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-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, such as the gamma ray data above 79.5 mbsf, 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).


Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 180. For further questions about the logs, please contact:


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