Standard Wireline Data Processing
Science operator: BP Exploration( Alaska), Inc.
Hole: Mt. Elbert-01
Location: Milne Point, North Slope (Alaska)
Latitude: 70° 27' 20.304" N
Longitude: 149° 24' 38.8434" W
Logging date: February, 2007
Total penetration: 914 m (from kelly bushing)
Permafrost depth: 595 m (from kelly bushing)
Casing depth: 595 m (24.4 cm)
Kelly bushing: 16.8 m above sea level. Depth reference for all logs.
Ground elevation: 6.5 m above sea level
Gas hydrate zones: 649.8-666.3 m (Unit C), 614.4-627.9 m (Unit D)
Lithologies: Clay, silty clay, sand, silty sand, and interbedded pebbles.
The logging data was recorded by Schlumberger in DLIS format. The data wasthen processed by Schlumberger Alaska and the results were reviewed at the Borehole Research Group of the Lamont-Doherty Earth Observatory in January, 2021. see d
| Tool string |
Pass
|
Top (m)
|
Bottom (m)
|
Casing (m)
|
Notes |
|
1. ZAIT/MCFL/TLD/HGNS/GPIT/EPT |
Main
|
571
|
912
|
595
|
|
|
|
Repeat
|
573
|
811
|
595
|
|
|
2. SonicScanner/OBMI/GPIT/EDTC |
Main
|
n/a
|
n/a
|
Tools failed. No data acquired. |
|
|
3. DSI/OBMI/GPIT/EDTC |
Main
|
n/a
|
n/a
|
Tools failed. No data acquired. |
|
|
4. DSI/OBMI/GPIT/EDTC
|
Main
|
582
|
914
|
595
|
|
|
Repeat
|
583
|
915
|
595
|
|
|
|
5. CMR/ECS/HNGS
|
Main
|
586
|
912
|
595
|
CMR tool failed. Only ECS and HNGS acquired. |
|
Repeat
|
593
|
718
|
595
|
CMR tool failed. Only ECS and HNGS acquired. |
|
|
6. CMR/HNGS
|
Main
|
611
|
807
|
open hole
|
|
|
Repeat
|
611
|
672
|
open hole
|
||
|
7. MDT
|
Station 1
|
657.1
|
660.2
|
open hole
|
Gas hydrate Unit C - Center point for test 658.7 m
|
|
Station 2
|
654.1
|
657.1
|
open hole
|
Gas hydrate Unit C - Center point for test 655.6 m | |
|
Station 3
|
622.4
|
625.5
|
open hole
|
Gas hydrate Unit D - Center point for test 623.9 m |
|
|
Station 4
|
615.7
|
618
|
open hole
|
Gas hydrate Unit D - Center point for test 617.2 m |
HGNS/MCFL/TLD = Platform Express
Mt. Elbert was initially drilled with LWD tools from the surface to the bottom of the permafrost at 595 m using a water-based mud. Casing was set at about 595 m and the hole was cemented. Susequent drilling with oil-based mud was carried out to a depth of 760 m, and 131 m of cores were succeesfully recovered. The hole was further deepened to a total depth of 914 m; 6 runs of wireline logging were then completed, followed by testing with the Modular Dynamic Formation Tester in the two gas hydrate reservoirs.
Post-acquisition processing was carried out by Schlumberger DCS Alaska and consisted of the following:
1. Depth control for all acquired runs
2. Processing of the Rt-Scanner (ZAIT) and Combinable Magnetic Resonance (CMR)
3. Spectrolith analysis of the Elemental Capture Spectrometry Sonde data (ECS)
4. Image processing with dips (OBMI)
5. Sonic Waveform Analysis (DSI)
6. Gas hydrate saturation analysis
7. Processing of the Combinable Magnetic Resonance data(CMR).
Depth match. The depth match reference was initially set to the gamma ray curve from the ZAIT/MCFL/TLD/HGNS/GPIT/EPT run. However, no depth match was necessary due to the excellent correlation between runs.
All logs depths are referred to the kelly bushing, which was 9.29 m above sea level.
Environmental corrections. Corrections for environmental conditions and type of mud used during the drilling were carried out by Schlumberger on density, neutron porosity and gamma ray logs. It is assumed that the logs reviewed by LDEO include data with such corrections.
Sampling rates:
- acoustic data: 15.24 cm (SonicScanner)
- caliper data: 15.24 cm (PPC), 2.54 cm (PEX)
- density data: 5.08 cm (TLD)
- gamma ray: 15.24 (and 5.08 cm (EDTC, HGNS), 15.24 cm (HNGS)
- geochemistry: 15.24 (ECS)
- inclinometry: 15.24 cm (GPIT)
- magnetic resonance: 5.08 cm (CMR)
- porosity: 15.24 and 5.08 cm (HGNS)
- resistivity data: 7.62 cm (RtScanner), 5.08 cm (MCFL)
Acoustic data. Both sonic data processed by Schlumberger and by Gilles Guerin at LDEO are inlcuded as output.
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). The data from the M Elbert-01 hole are of excellent quality.
Gamma ray logs recorded through the casing should be used only qualitatively, because of the attenuation of the incoming signal.
Hole diameter was recorded by the caliper on the TLD-PEX (HCAL) and by the Power Positioning Caliper tool (HD1, HD2, HD3) on the OBMI tool string. )
A Null value of -999.25 may replace invalid log values.
Additional information about the drilling and logging operations can be found in the Geological Survey of Canada Bulletin 601 (https://doi.org/10.4095/291751).
For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.