The Silurian shales of central and western North Greenland: evaluation of hydrocarbon source rock potential

H Nøhr-Hansen,F.G Christiansen

doi:10.34194/rapggu.v143.8057

Abstract

The Silurian shales of central and western North Greenland form a more than 400 m thick succession which contains some potential hydrocarbon source rock intervals. Deposition of these organic-rich units was restricted in both time and space and potential source rocks only formed when and where black shales covered wide areas of sballow-water carbonates. Such deposition started in the middle Llandovery in Washington Land and continued tboughout the region in the late Llandovery. Neither the Wenlock nor the Ludlow shales contain sufficient organic matter to be considered as potential source rocks. The potential source rocks are dominated by oil-prone organic matter (large amorphous kerogen particles, mainly type Il) and typically show TOC values between 2% and 6%. The generative potential of immature to early mature samples is high with values up to 30 mg Hag rock. A drastic increase in thermal maturity of surface rocks is observed from south to north and most of the potential drainage area is thermally mature to postmature. This leaves only few chances of finding trapped hydrocarbons sourced by Silurian shales in North Greenland.

Highlights

The Silurian shales of central and western North Greenland form a more than 400 m thick succession which contains some potential hydrocarbon source rock intervals
The potential source rocks are dominated by oil-prone organic matter and typically show Total Organic Carbon (TOC) values between 2% and 6%
A drastic increase in thermal maturity of surface rocks is observed from south to north and most of the potential drainage area is thermally mature to postmature

Summary

CARBONATE MUOSTONE

Few samples from the mature area in Nares Land have slightly higher values Both the group C and D shales have a poor potential with values lower than 2 mg HC/g rock (figs 13 and 14). The early mature source rocks from Washington Land (Tmax = 438°C) have generated minar amounts of hydrocarbons which locally have migrated into interbedded conglomerates The remaining postrnature samples (Tmax = 477°C) have no residual potential, all hydrocarbons having been expelled or cracked These values indicate that very large amounts of hydrocarbons were generated in the group A shales before and during the time of deepest subsidence and strongest thermal alteration. 5) The organic matter in the source rocks is dominated by large amorphous kerogen particles, probably with marine algae as precursor

OB oCl

Findings

65 APPENDIX Sedimentary logs of the six Silurian cores