IODP Expedition 325, Hole M0054B - Wireline Standard Data
IODP-MSP drilling and logging contractor: ESO
Hole: M0054B
Expedition: 325
Location: Great Barrier Reef (tropical SWF Pacific Ocean)
Latitude:17 ° 6.0425' S
Longitude: 146° 34.60458' E
Logging date: March 30, 2010
Sea floor depth (driller's): 110.33 m DSL
Sea floor depth (logger's): 126.25 m WRF on ASGR; 120 m WRF on all other tools
Total penetration: 33.2 m DSF
Total core recovered: 8.25 m 24.85 ( % of cored section)
Lithologies: carbonate sand, corals, bioclastic sediments
The logging data was recorded by the
|
Tool string |
Pass |
Top depth (m WMSF) |
Bottom depth (m WMSF) |
Pipe depth (m WMSF) |
Notes |
|
1. ASGR |
Uplog |
0 |
33.2 |
Recorded through pipe |
|
|
2. DIL45 |
Downlog |
0 |
26.3 |
17.52
|
|
|
3. DIL45 |
Uplog |
0 |
26.3 |
17.52
|
|
|
4. ABI40 |
Uplog |
16.3 |
25.5 |
17.52
|
|
|
5. OBI40 |
Uplog |
15.5 |
25.2 |
17.52 |
|
|
6. ASGR |
Uplog |
0 |
26.3 |
17.52 |
|
|
7. 2PSA |
Uplog |
2.1 |
23.6 |
17.52 |
|
|
8. EM51 |
Downlog |
0 |
24.2 |
17.52 |
|
|
9. EM51 |
Uplog |
0 |
23.9 |
17.52 |
|
|
10. IDRONAUT |
Uplog |
17.5 |
26 |
17.52 |
|
|
11. 2PCA |
|
13.6 |
24 |
17.52 |
|
Hole M0054B was the first hole where geophysical wireline operations could be performed in a HQ ("logging") hole, ideal to run the high-priority imaging tools. Logging operations began with a through-pipe spectral gamma ray log (ASGR) followed by open-hole logs: resistivity (DIL45), acoustic borehole televiewer (ABI40), optical borehole televiewer (OBI40), spectral gamma (ASGR), sonic (2PSA), magnetic susceptibility (EM51), Idronaut and caliper (2PCA) sondes. Hole stability for open-hole logging was relatively good.
Depth shift: The original logs were corrected for tool zero (ASGR TP: +0.19 m, DIL45: +0.12 m, ABI40: +0.38 m, ASGR OH: +0.16 m 2PSA: +0.26, EM51: +0.27, Idronaut: +0.2, 2PCA: +0.16) and shifted to the sea floor (- 126.25 m WRF for ASGR256 TP, - 120 m WRF for all other logs). At this hole, each tool was run on an individual string with no repeated measurements between strings; the open hole (OH) gamma ray log was matched to the gamma ray log measured through pipe, and then the pipe depth kick in all other logs were matched to the pipe kick of the OH gamma log (additional small shifts were made to specific logs: deep conductivity: -13.54 m UL, -15.28 m DL; medium conductivity: -15.45 m UL, -15.39 m DL; magnetic susceptibility: -15.97 m DL, -15.92 m UL; IL: -15.24 m DL, -15.24 m UL, FWS sonic: -15.2 m UL; ASGR256 OH: -3.4 m UL; ABI40: -15.331 m UL; OBI40: -15.008 m UL, Caliper: -15.64 m UL; Idronaut: -13.15 m DL, -11.98 m UL). Due to shallow water and hole depths and maintaining a fixed zero position at the top of the drill pipe, depth discrepancies between logs are minimal.
Environmental corrections: None were applied.
Acoustic data: The 2PSA tool was run at a frequency of 15 kHz. 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).
The quality of the data is assessed by checking against reasonable values for the logged lithologies 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 data allows for the identification of two logging units, though lithostratigraphic and logging unit boundaries do not perfectly concur. However, core recovery in this hole was only 29 %.
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.
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 325.
For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.