IODP-MSP
drilling and logging contractor: ESO
Hole: M0009E
Expedition: 310
Location:
Latitude: 17° 29.3142' S
Longitude:
149° 24.2121' W
Logging
date: November 9,
2005
Sea
floor depth (driller's): 108.7 mbrf (94.94 mbsl)
Sea
floor depth (logger's): 108.7 mbrf
Total
penetration: 19.4
mbsf
Total
core recovered:
14.11 m (72.73 % of cored section)
Oldest
sediment recovered:
Pleistocene sequence
Lithologies: Reef framework, algal crusts, and
microbialite matrix
The logging data was
recorded by the
Tool string |
Pass |
Top depth
(mbsf) |
Bottom depth
(mbsf) |
Pipe depth
(mbsf) |
Notes |
1. DIL45 |
Pass 2 |
2.89 |
15.09 |
2.55 |
|
2. ABI40 |
|
2.14 |
15.70 |
2.55 |
|
3. OBI40 |
Main |
2.04 |
14.64 |
2.55 |
Poor quality : not used |
4. ASGR |
Main |
0 |
14.92 |
2.55 |
|
5. IDRONAUT |
Main |
1.63 |
14.53 |
2.55 |
|
6. 2PCA |
Main |
1.45 |
14.51 |
2.55 |
|
7. 2PSA |
Pass 1
|
2.55 |
11.39 |
2.55 |
|
8. 2PSA |
|
2.55 |
11.39 |
2.55 |
|
A complete
list of tool and log acronyms is available at http://brg.ldeo.columbia.edu/data/iodp-eso/exp310/exp_documents/iodp-eso-310-acronyms.html.
After completion of the coring, the drill string was pulled and the coring bit was changed for an open shoe casing to provide borehole stability in unstable sections and a smooth exit and entry of logging tools. In addition, a wiper trip was performed with fresh sea water (no drilling mud was used). Difficult borehole conditions often required the boreholes to be logged in key intervals where the HQ drill string was used as a temporary casing. All measurements were performed under open borehole conditions (no casing) with the exception of a few spectral gamma ray logs which were run through the steel pipes to obtain continuous geophysical information over the entire interval cored.
Hole M0009E
was drilled and logged during Expedition 310. Logging operations were conducted
from 14.92 mbsf upwards with data coverage in the open borehole without
repositioning the open shoe casing (fixed at 2.55 mbsf) by all tools except the
OBI40. Borehole conditions were hostile and the borehole was highly unstable,
particularly below 11 mbsf. The calipers show a large increase in borehole
diameter below this depth and the logging tools could not pass an obstruction
at 15 mbsf even after repetitive cleaning and hammering efforts. Although the
optical tool was deployed, the quality is too poor for the log to be used due
to cloudy borehole fluids. Sonic velocities towards the base of the logged
interval are of poorer quality in the regions where the framework is most open.
The depths
in the table are for the processed logs (after applying a depth shift to the
sea floor). 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 the 'bottom felt' depth in soft sediment. However, for
Depth
shift: The original logs were first shifted to the sea floor
using the driller’s depth to seafloor (-108.7 m below rig floor). For
Environmental
corrections: None were applied.
Acoustic data: The 2PSA tool was run at a frequency of 10 kHz in Pass 1 and 1 kHz in Pass 2 in order to calculate compressional and Stoneley velocities respectively. The data was filtered (frequency filter) in such a way that only the energy around the induced frequency (source) was analyzed. Waveform picking was done manually in the LogCrucher software package to ensure good quality data. Time picks were saved and the acoustic velocities were calculated (using the receiver spacing of 1 ft). All presented acoustic data is accurate. Where no clear first arrivals in the waveform were present in at least two receivers, a value of zero was entered in the database.
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 acoustic log).
The quality of the ASGR Spectral Natural Gamma data is
directly related to lithology in combination with logging speed. Despite
logging speeds of 1.1 m/minute and a taking a sample every 10 cm (collecting
gamma ray emissions of the formation for approximately 6 seconds for every
sample) the amount of total counts obtained are still very low. This degrades
the quality of the statistics that separates the raw counts into activity
values of naturally occurring radioactive elements such as potassium (K),
uranium (U) and thorium (Th). Negative K values are indicative of incorrect
statistics. Gamma ray logs
recorded through drill pipe should be used only qualitatively due to
attenuation of the incoming signal. Gamma ray logs recorded through drill pipe
should be used only qualitatively due to attenuation of the incoming signal.
Due to a short time period between the completion of coring
(including wiper trip) and logging, the IDRONAUT data should be treated with
great care. The hydrological properties of the borehole fluid measured with
this tool represent more of a mixture between fresh sea water (used for coring
and for the wiper trips) and true formation pore water.
A wide
and/or irregular borehole affects most recordings, particularly those that
require eccentralization and a good contact with the borehole wall. Hole
diameter was measured by the caliper tool (2PCA) and can also be calculated
from the acoustic imaging tool (ABI40).
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 section of the Site Chapter in IODP Proceedings of Expedition 310.
For further questions about the data, please contact:
Jennifer
Inwood
University
of Leicester
Phone:
011-44-116-252-3327
Fax: 011-44--116-252-3918
E-mail: iodp@le.ac.uk
For any web
site-related problem please contact:
E-mail: logdb@ldeo.columbia.edu