Sedimentary Evolution and Reservoir Prospective of Bashkirian-Moscovian Mixed Siliciclastic-Carbonate Deposits in the Loppa High (Norwegian Barents Sea)

Di Lucia, Matteo ¹; Sayago, Jhosnella ¹; Mutti, Maria ¹; Cotti, Axum ²; Broberg, Kjetil ²; Sitta, Andrea ²
(1)Institut für Erd- und Umweltwissenschaften, Universitaet Potsdam, Potsdam, Germany. (2) Edison International S.p.A (Norway Branch), Stavanger, Norway.

The Loppa High, in the Norwegian Barents Sea, is a buried isolated structural feature. The sedimentary evolution of the Bashkirian-Moscovian sequence shows, in addition to eustatism, the effects of local to regional tectonic starting from the Late Carboniferous. This study has investigated a core section (283 m thick) characterized by Late Bashkirian conglomerate-dominated marine to continental deposits, which develop upwards to cyclically interbedded marine siliciclastics and subtidal carbonates. The upper interval is exclusively dominated by Early Moscovian peritidal carbonates of the Gipsdalen Group, considered a major reservoir-prone unit of the Upper Paleozoic of the Barents Sea. On the other hand, the Bashkirian-Moscovian units of the reservoir-prone Gipsdalen Group have received little interest in the Barents Sea region, and even less on the Loppa High.

This study has been focused in a first step on the identification of the main features such as lithology, texture, visible porosity and permeability, sedimentary structures and biotic content. Eight Lithofacies Associations (LAs) have been then identified, and have provided the basis to define depositional facies models that reflect the environmental evolution of the complex Loppa High system through time. Metric to decametric shallowing- and deepening- upward trends have been individuated, superimposed on a 3rd order Bashkirian to Early Moscovian transgressive depositional trend, also recognizable in other areas of the western Barents Sea. The post-depositional history of the section reveals a strong diagenetical overprint mainly affecting the carbonates deposits through different phases of extensive dolomitization and silicification. The analysis of measured porosity and permeability trends of the carbonate sediments across the section and through cross-plots shows that the two parameters are mostly independent by facies variations across the section. This allows developing preliminary conclusions about a potential strong control of post-depositional processes on the reservoir potential of these rocks.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.