Integrated analysis of vitrinite reflectance, Rock-Eval 6, gas chromatography, and gas chromatography-mass spectrometry data for the Reindeer D-27 and Tununuk K-10 wells, Beaufort-Mackenzie Basin, northern Canada
Authors: Issler D R , Jiang C , Reyes J , Obermajer M 
Published: April 2016

Core and cuttings samples were selected from the Reindeer D-27 and Tununuk K-10 wells for detailed Rock-Eval/TOC, vitrinite reflectance, gas chromatography, and gas chromatographymass spectrometry analysis as part of a regional thermal maturity study of the
Beaufort- Mackenzie Basin in Arctic Canada. These deep and extensively cored wells, located at the southern end of Richards Island in the thrusted eastern margin of the Taglu Fault Zone (Tununuk High), provide a useful reference for interpreting new and legacy Rock-Eval data for cuttings samples
that are known to be susceptible to contamination. Organic petrological observations and elevated Rock-Eval Tmax values indicate that recycled organic matter is common in the Iperk, Richards and Taglu sequences of the Reindeer D-27 well, and the Iperk, Aklak, Fish River and Arctic Red successions of
the Tununuk K-10 well. Samples from both wells show evidence of contamination based on anomalous Rock-Eval pyrograms (e.g. multi-modal, asymmetric) and anomalous Rock-Eval parameters such Tmax, S1 and PI. For the Reindeer D-27 well, oil staining, hydrocarbon fluid inclusions, exudatinite (early and
locally generated waxy oil from terrestrial organic matter) and bitumen have been observed in samples from the Taglu, Aklak and Arctic Red successions and these are associated with elevated PI and reduced Tmax values. Oil staining and bitumen have been observed in some samples from the Tununuk K-10
well also. Tmax values are low and decrease with increasing TOC content in the abundant, immature to marginally mature coal-rich samples of the Taglu Sequence in the Reindeer D-27 well. Some post-drilling contamination of samples is indicated by the presence of the plasticizer, dibutylphthalate
(from plastic sample vials), in extracts of cuttings samples from the Reindeer D- 27 well. Although such contamination can contribute to anomalous Rock-Eval parameters, the observed elevated S1 values and reduced Tmax values for cuttings samples relative to core samples for both wells suggests that
drilling mud additives are the main source of contamination.
Measured mean random reflectance for indigenous vitrinite varies from 0.37 %Ro (Richards Sequence) to 0.79 %Ro (Arctic Red Formation) for the Reindeer D-27 well and 0.39 %Ro (Aklak Sequence) to 1.30 %Ro (Arctic Red Formation) for the Tununuk K-10 well. The unconformably overlying
Iperk Sequence in both wells is thermally immature and dominated by recycled vitrinite. Rock-Eval, apatite fission track, and biomarker (sterane and terpane) isomer ratio data provide independent confirmation of organic maturity levels. In accordance with previous published studies, petrological,
Rock-Eval and organic geochemical data indicate that the Cretaceous Smoking Hills/Boundary Creek and Arctic Red Formations are dominated by marine (Type II) organic matter whereas the overlying mainly Cenozoic, deltaic sediments contain abundant terrestrially-derived organic matter (Type III).
Thermal modelling, constrained using maturity and biomarker data, suggests that marine Cretaceous rocks in both wells entered the oil window at 135°C and reached peak generation at approximately 145°C during late Eocene-Oligocene time. The distribution of n-alkanes and alkyl naphthalenes
in extracts of Taglu cuttings samples suggests that oil migrated from the Arctic Red Formation into the overlying Taglu and probably Aklak sequences in the Reindeer D-27 well. Good results are achieved using the new basin%Ro kinetic model for vitrinite reflectance with constant geothermal
gradients equal to present values of 25.2°C/km and 28.6°C/km, and with pre-Iperk eroded thicknesses of 2200 m and 2300 m, for the Reindeer D-27 and Tununuk K-10 wells, respectively. The popular EASY%Ro kinetic model gives poorer results that may indicate a systematic miscalibration of
vitrinite reflectance with respect to temperature for this model.