Integrated analysis of vitrinite reflectance, Rock-Eval 6, gas chromatography, and gas chromatography-mass spectrometry data for the Mallik A-06, Parsons N-10 and Kugaluk N-02 wells, Beaufort-Mackenzie Basin, northern Canada
Authors: Issler D R , Obermajer M , Reyes J , Li M 
Published: June 2012

Core and cuttings samples were selected from the Mallik A-06 (Mackenzie Delta), Parsons N-10 (Tuktoyaktuk Peninsula) and Kugaluk N-02 (Anderson Plain) wells of the Northwest Territories for Rock-Eval/TOC and vitrinite reflectance analysis. Selected Rock-Eval
samples were extracted and analysed using gas chromatography and gas chromatographymass spectrometry. Rock-Eval parameters are strongly affected by sample contamination from drilling mud additives and migrated oil. For the Mallik A-06 well, most Rock-Eval pyrograms in the Iperk, Mackenzie Bay and
Kugmallit sequences show evidence of drilling mud contamination. Approximately 50% of the pyrograms in the Richards and Taglu sequences are anomalous and GC-MS and GC-MS-MS analysis for selected extracts indicate extensive contamination by migrated and biodegraded Upper Cretaceous (Boundary
Creek/Smoking Hills formations) derived oil. For the Parsons N-10 well, coal samples within the Iperk and Aklak sequences have anomalous pyrograms that are probably related to their low level of maturity. However, most pyrograms from the Cenozoic (Iperk and Aklak sequences) and Upper Cretaceous
(Mason River, Smoking Hills and Boundary Creek sequences) successions show evidence of significant sample contamination. The upper part of the Albian Arctic Red formation shows similar contamination but there is an abrupt change below a depth of 2195 m where most pyrograms appear to be normal within
the Lower Cretaceous-Upper Jurassic succession. For the Kugaluk N-02 well, all pyrograms have been disturbed by contamination from oil-based mud and yield low Tmax values as a result.
Tmax thermal maturity estimates for the least disturbed pyrograms show very good agreement with measured vitrinite reflectance values for the Mallik A-06 and Parsons N-10 wells. Measured mean random vitrinite reflectance varies from 0.23 (Iperk Sequence) to 0.65 %RoR (Taglu Sequence) for the
Mallik A-06 well and 0.25 (Iperk Sequence) to 0.66 %RoR (Husky Formation) for the Parsons N-10 well. A number of vitrinite reflectance measurements for samples from the Richards and Taglu sequences in the Mallik A-06 well have been suppressed due to staining by migrated Cretaceous-derived oil.
The Paleozoic succession in the Kugaluk N-02 well is overmature with measured vitrinite reflectance values ranging from 1.6 (Imperial Formation) to 2.0 %RoR (Landry Formation) over a 960 m depth interval. Extrapolated maturity is 2.7 %RoR in the Franklin Mountain Formation at the base of
this well. There is qualitative agreement between the expected and observed degree of apatite fission track annealing for apatite fission track samples in all three wells and this provides independent support for the thermal maturity estimates. Exponential curves were fit to the %RoR-depth data
and extrapolated to an initial surface value of 0.2 %RoR to obtain estimates on the magnitude of erosion at each well location. For the Mallik A-06 and Parsons N-10 wells, the estimated thickness of strata eroded prior to the deposition of the Iperk Sequence is approximately 700 and 1300 m,
respectively. For the Kugalik N-02 well, the modest maturity gradient implies that up to 8 km of strata may have been removed by erosion.