Standard Wireline Data Processing
IODP drilling and logging
operator: CDEX
Hole: C0020A
Expedition: 337
Location: Offshore Shimokita Peninsula (Japan Sea)
Latitude: 41° 10.5983' N
Longitude: 142° 12.0328' E
Logging date:
Sea floor
depth (driller's):
1208.5 m DRF
Sea floor
depth (logger's):
1208.5 m WRF
Total
penetration: 3674.5 m DRF ( 2466 m DSF)
Total core
recovered: 198.4 m (75.3 % of the 263.5 m cored interval)
Oldest sediment recovered: Oligocene-Early Miocene
Lithologies: Diatom-rich silty clay, shale, sandstone, siltstone, coal-rich horizons
The logging data
was recorded by Schlumberger in DLIS format. Data were processed at the
Borehole Research Group of the Lamont-Doherty Earth Observatory in April 2014.
| Tool string | Pass
|
Top depth (m WSF) | Bottom depth (m WMSF) | Casing depth (m WMSF) | Notes |
1. HRLA/TLD/HGNS/MCFL/HNGS
|
casing
|
1252.9 |
|
||
main
|
|
1252.9 |
|||
repeat
|
1252.9 |
||||
2. FMI/DSI/GPIT/EMS/EDTC |
casing
|
1252.9 |
|||
main
|
1252.9 |
||||
repeat
|
1252.9 |
||||
3. CMR/EDTC |
main
|
1252.9 |
|||
repeat
|
1252.9 |
||||
4. MDT/EDTC |
1252.9 |
6 sampling stations |
|||
5. VSI/EDTC |
1252.9 |
129 stations |
Wireline logging operations started after drilling and coring to a depth of 2466 m DSF. The passive heave compensator was setup in preparation for logging. The 13 3/8" casing shoe was set at 1252.9 m DSF.
The first deployment, consisting of the HRLA/TLD/HGNS/MCFL/HNGS tool string, acquired data in a main and repeat section. Gamma ray data were acquired thru casing as well.
The second tool string, FMI/DSI/GPIT/EMS/EDTC, also acquired a main, repeat and thru-casing sections.
The CMR (Combinable Magnetic Resonance) tool was run next and acquired a main and repeat section. The fourth deployment consisted of the Modular Formation Dynamic Tester (MDT), whose measurements are used to determine the formation's permeability and fluid pore volume. It acquired bottle samples at 6 stations.
The VSI (Versatile Seismic Imager) was run last and acquired data in 129 stations.
The depths in the table are for the processed logs (after depth shift to the sea floor ).
Depth shift to sea floor and depth match. The original logs were shifted to the sea floor (- 1208.5 m). This value corresponds to the sea floor depth given by the drillers (see above), as no logging run reached the sea floor.
The depth-shifted logs did not need to be depth-matched to the gamma ray log from a reference run as there was excellent correlation among all logging passes; therefore, the depths given in the ASCII files are expressed as m WMSF (same as m WSF).
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 no sudden changes in cable speed), and then the features in the
equivalent logs from the other runs are matched to it in turn. This matching is
performed manually. 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, EDTC
and HRLA are typically corrected for hole size during the recording. However, the documentation downloaded from the JAMSTEC SIO7 Data Center web site
Acoustic
data. The dipole shear
sonic imager (DSI) was operated in the following modes: P&S monopole
(all passes), cross-dipole (main and repeat), and upper and lower dipole (partially thru casing). The sonic waveforms were processed onshore by Schlumberger and then delivered via satellite back to the ship. The ASCII files presented in the database include the original delay times (DTCO, DT1, DT2) and the compressional and shear velocities were computed by Schlumberger for the main section. The repeat section includes only the original delay times. The data are
generally of good quality.
The quality of
the data is assessed by checking against reasonable values for the logged
lithologies, by repeatability between different passes of the same tool, and by
correspondence between logs affected by the same formation property (e.g. the
resistivity log should show similar features to the sonic velocity log).
The quality of the logs acquired in Hole C0020A is generally excellent, due to a stable borehole and the absence of washouts or other irregularities of the borehole wall.
Gamma ray logs recorded through the casing should be used only qualitatively, because of the attenuation of the incoming signal and the presence of casing joints. Any acoustic data acquired through casing is also largely affected by the thick (13 3/8") casing walls.
Irregularities and enlargements of the borehole affect most recordings, particularly
those like the TLD (density tool) that require eccentralization and a good contact with the borehole wall. Hole diameter was recorded by the hydraulic caliper on the TLD
tool and by the FMS tool (C1 and C2). The hole is in gauge and shows ideal conditions for logging.
A null value of
-999.25 may replace invalid log values.
Additional information about the drilling and logging operations can be found in the Operations and Downhole Measurements sections of the expedition report, Proceedings of the Integrated Drilling Program, Expedition 337. For questions about the database, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia
For questions about the logs, please contact:
Yoshinori Sanada
E-mail: sanada@jamstec.go.jp
Yukari Kido
Email: ykido@jamstec.go.jp
Yuichi Shinmoto
Email: shinmoto@jamstec.go.jp