Triassic-Jurassic reservoir quality evolution in Central East Greenland

In the North Atlantic region it is well established that Triassic sandstones form poorer quality reservoirs for hydrocarbon than Jurassic sandstones. However, the reasons for this are not clearly understood. The best place in the region to investigate the cause for this improvement in reservoir quality is the Jameson Land Basin of East Greenland. The Triassic and Jurassic clastic successions are thick, well-exposed and there are few breaks in sedimentation.

The Jameson Land Basin is located between 71º12’ and 72º25’N. It is a north-south aligned rift basin about 280 km long and 80 km wide. Development of accommodation space during the Triassic and Jurassic was driven by rifting in the Early Triassic, Mid Triassic and Middle to Late Jurassic. During this time there is a shift in depositional environment from continental to shallow marine with the transition occurring in the Early Jurassic. Greenland drifted northwards from around 30ºN, in the northern arid climatic belt in the Early Triassic to around 60ºN by the Late Jurassic.

To investigate the changes in reservoir quality, sandstones were analysed petrographically and porosities and permeabilities measured using core plugs. This was combined with clay mineralogical work on sandstones and mudstones throughout the succession and by heavy mineral analysis to investigate the controls on reservoir quality. Petrography, porosity and permeability work indicate the main improvement in reservoir quality occurred between the Late Triassic and Early Jurassic. The clay mineralogical work reveals that this change is controlled by a trend towards more humid climatic conditions. Provenance variations do not have a significant influence. A strong link is therefore shown between climate and the improvements in reservoir quality.