IODP-MSP drilling and logging
contractor: ESO
Hole: M0077A
Expedition: 364
Location: Chicxulub Impact Crater (Gulf of Mexico)
Latitude: 21° 27.009' N
Longitude: 89° 56.962' W
Logging date: April 14-15
(upper section), May 1-4 (middle section), May 26-28 (lower section)
Sea floor depth
(driller's): 34.2 m DRF
Sea floor depth
(logger's): 33.94 m
WSF
Total penetration: 1368.89 m DRF (1334.69 m DSF)
Total core
recovered:
839.51 m (100 % of cored section)
Oldest sediment recovered: Paleogene
Lithologies: Carbonates, granite, melt
For Expedition 364, slimhole downhole logging services managed by the European Petrophysics Consortium (EPC) have been contracted by the University of Montpellier (France) for wireline logging and by the University of Alberta (Canada) and Texas at Austin (USA) for the vertical seismic profiling (VSP).
Wireline logging data were acquired in TDF format and processed by the EPC with the log software package WellCad. Raw data are provided online in DLIS format. Processed standard data are available in ASCII format while borehole images are available in JPG and PDF format.
The wireline logs were recorded either with stand-alone logging tools or with stackable tools combined into tool strings.
VSP data were processed by the University of Alberta. Both raw and processed data are provided in SEGY format.
UPPER SECTION
(April 14-15, 2016)
Run 1: DLL3 (standalone tool). Pass 1 and 2
Run 2: ABI40/SGR40. Downlog, Pass 1-3
VSP session
Run 3: EM51 (standalone tool). Downlog and uplog
Run 4: ABI40/SGR40. Pass 4
Run 5: OCEAN40/FWS40/SGR40. Pass 1 and 2
Run 6: OBI40/SGR40. Pass 1 and 2
MIDDLE SECTION
(May 1-4, 2016)
Run 1: DLL3 (standalone tool). Dowlog 1 and 2, Uplog
Run 2: FTC40 FWS40/SGR40. Downlog, Pass 1 and 2
Run 3: ABI40/CAL40/SGR40. Pass 1-9
VSP session
Run 4: ABI40/SGR40. Uplog acquisition test through casing
LOWER SECTION,
INTERVAL A (May 26-28, 2016)
Run 1: DLL3 (standalone tool). Downlog and uplog
Run 2: FTC40/FWS40/SGR40. Downlog, Pass 1 and 2
Run 3: EM51 (standalone tool). Downlog. Pass 1-4
Run 4: ABI40/CAL40/SGR40. Downlog, Pass 1-5
Run 5: OBI40/CAL40/SGR40. Uplog
LOWER SECTION,
INTERVAL B (May 26-28, 2016)
Run 6: DLL3 (standalone tool). Downlog and uplog
Run 7: FTC40/FWS40/SGR40. Downlog and uplog
Run 8: ABI40/SGR40. Pass 1-3
Run 9: EM51 (standalone tool). Downlog and uplog
Run 10: ABI40/CAL40/SGR40. Downlog, Pass 4-7
Run 11: FTC40/SGR40. Downlog 1-3, static
Run 12: OBI40/CAL40/SGR40. Pass 1-4
VSP session
The logging data presented in the following table were processed by the European Petrophysics Consortium.
Processed Logging Data
|
Tool |
Section/Interval |
Top
depth (m WSF) |
Bottom
depth (m WSF) |
Pipe
depth (m WSF) |
Remarks |
|
DLL3 |
UPPER |
21 |
465 |
20.1 |
merged, pass 1-2
|
ABI40
|
UPPER
|
0
|
498
|
20.1
|
merged,
pass 1-4
|
|
EM51 |
UPPER |
21 |
498 |
20.1 |
uplog
|
|
OBI40 |
UPPER |
56 |
91 |
20.1 |
merged, pass 1-2
|
|
OCEAN40 |
UPPER |
20 |
463 |
20.1 |
pass 2
|
FWS40
|
UPPER
|
461
|
490
|
20.1
|
pass 1 |
|
SGR40 |
UPPER |
0 |
496 |
20.1 |
merged, pass 1-4 from ABI40 string
|
|
EM51 |
MIDDLE |
507 |
696 |
507.3
|
uplog |
|
FTC40 |
MIDDLE |
507 |
698 |
507.3
|
pass 1
|
|
FWS40 |
MIDDLE |
508 |
697 |
507.3
|
pass 1 |
ABI40
|
MIDDLE |
506
|
697
|
507.3
|
merged, pass 1-8
|
|
SGR40 |
MIDDLE |
503 |
694 |
507.3
|
merged, pass 1-8 from ABI40 string
|
|
DLL3 |
LOWER/A |
940
|
1333 |
938.7
|
uplog |
FTC40
|
LOWER/A
|
939
|
1334
|
938.7
|
pass 1
|
FWS40
|
LOWER/A
|
939
|
1333
|
938.7
|
pass 1
|
|
EM51 |
LOWER/A |
940 |
1333 |
938.7
|
merged, |
ABI40
|
LOWER/A
|
939
|
1334
|
938.7
|
merged, pass 1-4
|
CAL40
|
LOWER/A
|
941
|
1112
|
938.7
|
|
|
OBI40 |
LOWER/A |
938 |
1044 |
938.7
|
uplog |
|
SGR40 |
LOWER/A |
940 |
1331 |
938.7
|
merged, pass 1-4 from ABI40 string |
DLL3
|
LOWER/B
|
701
|
955
|
700.8
|
uplog
|
EM51
|
LOWER/B
|
701
|
956
|
700.8
|
uplog
|
FTC40
|
LOWER/B
|
698
|
1332
|
700.8
|
merged,
pass 1-3 downlog
|
FWS40
|
LOWER/B
|
700
|
934
|
700.8
|
uplog
|
|
ABI40 |
LOWER/B |
682 |
936 |
700.8
|
merged, pass 1, 4-7
|
|
CAL40 |
LOWER/B |
698 |
848 |
700.8
|
merged, pass 4 and 6
|
|
OBI40 |
LOWER/B |
694 |
767 |
700.8
|
merged, pass
1-4
|
|
SGR40 |
LOWER/B |
678 |
932 |
700.8
|
merged, pass 1, 4-7 from ABI40 string |
The depths in the table above 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 and tides, but as the logging for Expedition 364 was performed from a platform resting directly on the sea floor no such corrections were necessary. Other reasons for depth discrepancies are wireline and pipe stretch, and the difficulty of getting an accurate sea floor form the 'bottom felt' depth in soft sediments.
Depth shift and depth match: One main processing task involves evaluating the depth of each logging run and referencing the data to the rig and sea floor. During the deployment of each stand-alone tool or tool string during the same logging session, a fixed zero-depth position (logger's zero) was maintained either at the top of the drill pipe or at the drill table. Using WellCad, the original logs were depth-adjusted to the rig floor (in meters wireline log depht below the rig floor, m WRF). This adjustment included several corrections:
Logs were subsequently shifted to the sea floor (meters wireline log depth below the sea floor, m WSF), which was recognized as the step in gamma radiation at the sediment/water interface. The applied vertical shift was 33.94 m for the entire log dataset.
Invalid log values have been replaced by a null value of -999.25. Invalid log values can include the following: 1) log data in pipe (DLL, EM51, ABI40, OBI40, some channels of the OCEAN40 and FWS40); 2) the effect on the tool response when approaching the steel pipe (DLL3, EM51 and some channels of the ABI40 and OBI40) in open hole conditions and 3) the lowermost data points in each logged interval.
Environmental correction: Environmental corrections are designed to remove any effect from the borehole (size, roughness, temperature, and tool standoff) or the drilling fluid that may partially mask or disrupt the log response from the formation. No post-acquisition corrections were applied at this hole.
Acoustic borehole images: Several corrections have been applied to the ABI40 data using WellCad software, including bad trace interpolation and image centralization. Images available in any format have been oriented with respect to the magnetic North. In some intervals, several passes have been oriented and merged on the same presentation. Images provided in PDF format (1:5 and 1:50 scales) are depth-corrected to the sea floor (m WSF) and are displayed as an unwrapped borehole cylinder.
Acoustic caliper values were obtained in WellCad with the Travel Time-to-Caliper Module using the WndTime log and assuming an acoustic wave velocity through the borehole fluid of 1,500 m/s .
Optical borehole images: Brightness and contrast of the OBI40 images have been automatically adjusted. Images available in any format have been oriented with respect to the magnetic north. In some intervals, several passes have been oriented and merged on the same presentation. Images provided in PDF format (1:5 and 1:50 scales) are depth-corrected to the sea floor (m WSF) and are displayed as an unwrapped borehole cylinder.
Sonic data: The FWS40 data were processed in WellCad to calculate the compressional velocity. Due to the good data quality below 460 m WSF, waveform picking was done automatically with the Standard Threshold Pickup Algorithm module and manually corrected or adjusted where needed. Time picks were saved and the acoustic velocities were calculated using the R1 and R2 receivers (spacing=20 cm). All the compressional velocities are accurate and correlate well with either the resistivity log or the acoustic borehole images. In the upper ~460 m of the hole the data quality was not good enough for automatic picking of the first arrival and therefore no data is provided. Further post-expedition processing is necessary for manual picking of the waveforms.
Spectral gamma ray data: Gamma ray logs recorded through drill pipe should be used
qualitatively only, due to attenuation of the incoming signal.
The spectral components of the gamma ray (U, Th, K) should be used with care since the total counts in the formation were low, with frequent negative values indicative of incorrect statistics. Potassium and Thorium values are below 3 cps and Thorium is null over the logged interval. Nonetheless the total gamma ray values appear to be reliable and correlate well with the NGR data measured on cores.
Resistivity and conductivity data: The DLL3 performs well in high resistivity formations. Due to the borehole width and the low resistivity of the formation in the upper interval, the DLL3 provides measurements that are not qualitatively reliable, especially the shallow readings. The induction conductivity measured by the EM51 tool (magnetic susceptibility and conductivity), which is more effective in high-conductivity formations, should be preferred in the upper interval.
Both the DLL3 and the EM51 worked well in the lower part of the hole.
In the middle interval, the DLL3 was not run. Due to tool communication issues, the EM51 data are of bad quality. Only a few data points have been acquired, every 1 to 5 meter. The processed logs contain interpolated data (maximum gap=2 m). The resulting data set, however, shows that the general log trend is in good agreement with one of the petrophysical measurements made on whole round cores, though the induction and magnetic susceptibility logs have a poor vertical resolution and show values that are lower than those from the cores.
Caliper data: Due to tool communication issues, the caliper arms did not open properly over some logged intervals. Data indicating diameters smaller than 15 cm have been deleted.
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 log).
The main influence on log quality are the borehole conditions. In Hole M0077A the borehole quality is generally excellent, with the exception of the upper 400 m, where the hole has an elliptical shape and karsts in the carbonatic formation are present. Both the sonic (FWS40) and acoustic televiewer (ABI40) logs were affected by the borehole quality over this interval. Measurements with a deeper depth of investigation were generally less sensitive to these borehole conditions. Below 400 m WSF the hole is almost in gauge with the drill bit diameter and the log data quality is generally excellent, with the exception of the EM51 and CAL40 logs, which presented communication issues during acquisition.
The response from the SGR40 tool should be used with care, especially through the pipe, where it has only a qualitative value.
The OCEAN40 and the FTC40 recorded uphole should be used qualitatively as well; the quality of these logs is best when they are acquired downhole once the borehole fluid has reached an equilibrium temperature with the formation and before other runs that may alter such an equilibrium.
Additional
information about the drilling and logging operations can be found in the
Operations section of the Site Chapter in IODP Proceedings of Expedition 364.
For
further questions about the logging data, please contact:
Johanna
Lofi
Géosciences Montpellier - UMR 5243 - CC 060 - Bat. 22
Université de Montpellier 2
Place E. Bataillon
34095 MONTPELLIER Cedex 05
France
Phone: 011-33-467-149-309
E-mail: johanna.lofi@gm.univ-montp2.fr
For any
web site-related problem please contact:
E-mail: logdb@ldeo.columbia.edu