Standard Wireline Data Processing
IODP logging
contractor: USIO/LDEO
Hole: U1440B
Expedition: 352
Location: Izu-Bonin Forearc (Philippine Sea)
Latitude: 28° 26.9976' N
Longitude: 142° 45.2244' E
Logging date:
Sea floor
depth (driller's):
4785.8 m DRF
Sea floor
depth (logger's):
4780.5 mWRF (FMS/DSI/GPIT/EDTC-B/HNGS Pass 2)
Total
penetration: 5169.4 m DRF (383.6 m DSF)
Total core
recovered: 34.71 m (12.3%)
Oldest sediment recovered: no data available
Lithologies: Volcanic basement overlain by 15 m of silty mud with volcanic gravel
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 August 2014.
| Tool string | Pass
|
Top depth (m WMSF) |
Bottom depth (m WMSF) |
Pipe depth (m WMSF) |
Casing depth (m WMSF) |
Notes |
1. UBI/HRLA/HLDS/GPIT/EDTC-B/HNGS
|
Downlog
|
94.5 |
99 |
Invalid caliper, HLDS and UBI | ||
Pass 1
|
open hole |
|||||
Pass 2
|
94.5 |
99 |
||||
2. FMS/DSI/GPIT/EDTC-B/HNGS
|
Downlog
|
213 |
94.5 |
99 |
Invalid FMS |
|
Pass 1
|
open hole |
|||||
Pass 2
|
94.5 |
99 |
Reference log |
The first tool string included the UBI/GPIT in addition to the HLDS/HRLA/EDTC-B/HNGS. No APS (porosity) tool was included. The tool string cleared the bit and casing shoe without incidents and reached a depth of 5039 m WRF, about 130 m above the hole total depth. After three attempts to pass a bridge failed, two uplogs were recorded. The FMS/DSI/GPIT/EDTC-B/HNGS tool string followed, which recorded one downlog and two uplogs without major incidents. Because of the calm sea conditions no WHC (Wireline Heave Compensator) was used during the logging operation.
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 reading 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 (-4780.5 m). The sea floor depth
was determined by the step in gamma ray values at 4780.5 m WRF on the FMS/DSI/GPIT/EDTC-B/HNGS (pass 2) logs. This differs by 5.3 m from the sea floor depth given by the drillers (see
above). The depth-shifted logs have then been depth-matched to the gamma ray log from pass 2 of the FMS/DSI/GPIT/EDTC-B/HNGS tool string.
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
and HRLA data were corrected for hole size during the recording. The HLDS data were corrected for hole size during the
recording.
High-resolution
data. High-resolution bulk density
(HLDS) data with a sampling rate of 2.54 cm were acquired for pass 2 only. They were missing for pass 1 due to an incorrect setting in the acquisition software.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 are smoothed to match the long-spacing ones, 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.
Gamma ray data from the EDTC-B tool were recorded with an additional sampling rate of 5.08 cm on all passes except for the downlog and first pass of the UBI/HRLA/HLDS/GPIT/EDTC-B/HNGS.
Acoustic data. The dipole shear sonic imager (DSI) was operated in the following four modes: P&S and upper dipole in low-frequency mode, lower dipole in standard frequency mode, and Stoneley for all passes. The sonic velocities were computed from the compressional (DTCO), shear (DT1 and DT2) and Stoneley (DTST) slownesses. Sonic data from the P&S and the lower dipole are generally better than that from the upper dipole and also in agreement with the resistivity data. However, reprocessing of the original sonic waveforms is highly recommended to obtain more reliable velocity results.
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).
Gamma ray logs
recorded through bottom hole assembly (BHA) and drill pipe should be used only
qualitatively, because of the attenuation of the incoming signal. The
thick-walled BHA attenuates the signal more than the thinner-walled drill pipe.
A wide
(>12") and/or irregular borehole affects most recordings, particularly
those that require eccentralization and a good contact with the borehole wall
(HLDS). Hole diameter was recorded by the hydraulic caliper on the HLDS
tool (LCAL) and by the FMS tool (C1 and C2). The hole size is about 11-14" for
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 352.
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