Standard Wireline Data Processing
IODP logging
contractor: USIO/LDEO
Hole: U1362A
Expedition: 327
Location: NE Pacific Ocean
Latitude: 47° 45.6628' N
Longitude: 127° 45.6720' W
Logging date: August 12, 2010
Sea floor
depth (driller's):
2672 m DRF
Sea floor depth (logger's): 2673.5 m WRF
Casing shoe (driller's):
Casing shoe (logger's):
Total
penetration: 3200 m DRF (528 m DSF)
Total core
recovered: 44.4 m (
30 % of cored section)
Oldest
sediment recovered:
N/A
Lithologies:
Highly fractured and altered basalt, both pillow and massive.
The logging data
were recorded by Schlumberger in DLIS format. Data were processed at the
Borehole Research Group of the Lamont-Doherty Earth Observatory in August 2010.
| Tool string | Pass
|
Top depth (m WMSF) | Bottom depth (m WMSF) | Casing depth (m WMSF) |
Notes |
1. UBI/HLDS/GPIT/HNGS/MTT
|
Downlog
|
305.5 |
Invalid HLDS |
||
2. UBI/HLDS/GPIT/HNGS/MTT |
Pass 1
|
307.5 |
|||
3. UBI/HLDS/GPIT/HNGS/MTT
|
Pass 2
|
275 |
308.5 |
Reference |
|
4. UBI/HLDS/GPIT/HNGS/MTT
|
Pass 3
|
Open hole |
Hole U1362A was cased with 16 in casing to a depth of 308.5 m DSF. Before logging, the hole was cleaned up through four wiper trips, but not displaced with drilling mud. The logging operations consisted of a downlog with the UBI/HLDS/GPIT/HNGS/MTT tool string, followed by three uplogs. All four passes reached close to the total depth without problems. The fourth uplog failed due to slightly damaged HLDS caliper arms.
The wireline heave compensator was run during the entire logging operation, though peak-to-peak heave was only about 0.5 m.
The depths in
the table are for the processed logs (after depth shift to the sea floor and depth matching between passes). Generally, discrepancies may exist between the
sea floor depths determined from the downhole logs and those determined by the
drillers from the pipe length. Typical reasons for depth discrepancies are ship
heave, wireline and pipe stretch, tides, and the difficulty of getting an
accurate sea floor from a 'bottom felt' depth in soft sediment.
Depth shift to sea floor and depth match. The original logs were first shifted to the sea floor (2673.5 m WRF). The sea floor depth was determined by the step in gamma ray values at 2673.5 m WRF from the downlog. This differs about 1.5 m from the sea floor depth given by the drillers (see above). The depth-shifted logs were then depth-matched to the gamma ray log from pass 2 (during which UBI images were aquired), which represented the best dataset.
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. Both HNGS and HLDS data were corrected for borehole size during the recording.
Temperature. Borehole temperature was recorded by the MTT tool (WTEP).
Quality Control
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 (HLDS) and a good contact with the borehole wall. Hole deviation can also affect the data negatively from UBI tool, which requires centralization of the tool string. Data recorded through casing 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 is about 12-18" for most of the section below the casing shoe (at 308.5 m WMSF). A slightly narrow and smooth section occurs at 456-472 m and a bridge at 376-379 m WMSF.
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 reports,
Proceedings of the Integrated Ocean Drilling Program, Expedition 327.
For further questions about the logs, please contact:
Tanzhuo Liu
Phone: 845-365-8630
Fax: 845-365-3182
E-mail: Tanzhuo Liu
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia