Standard Wireline Data Processing
Science operator: Imperial Oil Ltd.
Hole: Mallik-L38
Location: McKenzie Delta, Northwest Territories, Canada
Latitude: 69° 27' 44" N
Longitude: 134° 39' 25" W
Logging date: 1972
Total penetration: 1843 m (from kelly bushing)
Permafrost depth: 640 m
Casing depth: 896.8 m
Kelly bushing: 9.9 m above sea level. Depth reference for all logs.
Ground elevation: 0.9 m above sea level.
Gas hydrate zones: 819.1-826 m, 889-914.4 m, 919.3-934.5 m, 945.5-957.1 m, 960.1-963.5 m, 972.3-982.4 m, 987.6-996.7 m, 1012.2-1015.3 m, 1075.9-1082.7 m, 1091.2-1111.3 m (from kelly bushing).
Lithologies: Sand, silty sand, and sandy silt with various amounts of clay.
Mallik-L38 was drilled and logged in 1972. The hole was logged in two phases: the permafrost interval was logged first with the DIL/LL8/BHC/SP/GR tools before the casing was installed at 896.8 m. The remainder of the hole from a total depth of 1399 m was logged with DIL/LL8/BHC/SP/GR/FDC/SNP/GR. No proprietary data in DLIS format was available; the following data were obtained from Tim Collett as Excel files and were edited and formatted at the Borehole Research Group of the Lamont-Doherty Earth Observatory in November 2020 to meet the requirements of the LogDB database.
| Tool |
Top (m)
|
Bottom (m)
|
Casing (m)
|
Notes |
|
BHC |
163
|
1399
|
896.8
|
Permafrost + sub-permafrost, merged |
|
CALI-FDC |
906
|
1399
|
896.8
|
Sub-permafrost |
|
CALI-SNP
|
347
|
585
|
open hole
|
Permafrost. Caliper only, no porosity data. |
| DIL |
165
|
1399
|
896.8
|
Permafrost + sub-permafrost, merged |
|
FDC
|
907
|
1399
|
896.8
|
Sub-permafrost |
|
GR
|
25
|
1399
|
896.8
|
Permafrost + sub-permafrost, merged |
| LL8 |
165
|
1399
|
896.8
|
Permafrost + sub-permafrost, merged |
|
SNP
|
920
|
1399
|
896.8
|
Sub-permafrost |
|
SP
|
164
|
1399
|
896.8
|
Permafrost + sub-permafrost, merged |
Depth match. No proprietary data was available, therefore no depth match is possible. It is possible that the available data was previously depth-matched.
All logs depths are referred to the kelly bushing, which is 9.9 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: all data have a sampling rate of 15.25 cm.
Acoustic data. The velocity was computed from the BHC delay time.
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 sonic velocity log). The quality of the logging data at the Mallik hole was locally greatly degraded by the size and rugosity of the hole. Hole stability was a recurrent problem in Mallik L38; the breakdown of gas hydrates contributed to the development of large breakouts. In the gas-hydrate bearing units below 897 m the quality of the acoustic data is severely affected by the presence of gas, as shown by the frequent cycle skipping. The user is cautioned to use acoustic data quantitatively.
An indication of the condition of the hole is given by the caliper measurement, which was obtained by the FDC tool in the sub-permafrost interval. In addition, a caliper measurement was also obtained by the SNP tool. The dataset received from Tim Collett, however, includes only a partial SNP caliper in the permafrost interval, and no caliper in the sub-permafrost section. Since no porosity data were acquired in the upper part of the hole, the SNP caliper measurement was possibly obtained while the SNP radioactive source was turned off.
A Null value of -999.25 may replace invalid log values.
Additional information about the drilling and logging operations can be found in Collett and Dallimore, 1998 (https://www.arlis.org/docs/vol1/ICOP/40770716/CD-ROM/Proceedings/PDF001189/030018.pdf).
For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.