Standard Wireline Data Processing
Science operator: JAPEX-JNOC-GSC
Hole: Mallik-2L38
Location: McKenzie Delta, Northwest Territories, Canada
Latitude: 69° 27' 40.71" N
Longitude: 134° 39' 30.37" W
Logging date: March 22-28,1998
Total penetration: 1150 m (from kelly bushing)
Permafrost depth: 640 m
Casing depth: 677 m
Kelly bushing: 8.41 m above sea level. Depth reference for all logs.
Ground elevation: 1.36 m above sea level.
Gas hydrate zones: 891-920 m, 931-993 m, 1010-1032 m, 1040-1056 m, 1060-1110 m (from kelly bushing)
Lithologies: Sand, silty sand, and sandy silt with various amounts of clay.
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 November 2020.
| Tool string |
Top (m)
|
Bottom (m)
|
Casing (m)
|
Notes |
|
1. HALS/MCFL/TLD/HGNS (Platform Express) |
94
|
576
|
Permafrost interval. |
|
|
2. DSI/AMS/SGT |
99
|
579
|
Permafrost interval. |
|
|
3. AIT/EMS/SP/SGT
|
676
|
1150
|
677
|
|
| 4. HALS/MCFL/TLD/HGNS (Platform Express) |
676
|
1150
|
677
|
|
|
5. DSI/AMS/SGT
|
676
|
1150
|
677
|
|
|
6. FMI/GPIT/HNGS
|
Data not available. |
Mallik-2L38 was drilled and logged in 1998. The open-hole logging program consisted of 6 different logging strings, with the first two acquiring data in the permafrost zone before the installation of the casing in the upper part of the hole (casing shoe at 677 m). No proprietary data was available. The permafrost data were obtained from Tim Collett in Novcember 2020.
Depth match. No proprietary data was available, so it is assumed that the data had already been depth matched. A comparison of the available gamma rays and other logs show an excellent depth correlation, therefore no further processing was required.
All logs depths are referred to the kelly bushing, which is 8.41 m above sea level.
Environmental corrections. None was applied to the resistivity and gamma ray logs but some corrections may have been applied previously.
Sampling rates:
- acoustic data: 15.24 cm (DSI)
- caliper data: 15.24 cm (EMS), 2.54 cm (PEX)
- density data: 2.54 cm
- gamma ray: 15.24 cm and 5.08 cm
- porosity: 5.08 cm (HGNS)
- resistivity data: 7.62 cm (AIT), 5.08 cm (HALS, MCFL)
- spontaneous potential: 15.24 cm
Acoustic data. The dipole shear sonic imager (DSI) was operated in the following modes: P&S monopole and upper dipole. The velocities were computed from the delay times. They are generally of very good quality.
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 at the Mallik hole is 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 hydraulic caliper on the TLD (HCAL) and AIT tools (HD1, HD2, HD3). The caliper data acquired by the FMI are not available.
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 544 (https://doi.org/10.4095/210723 ).
For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.