| Summary: | The Triassic Skagerrak deposits of the Crawford Field, northern North Sea (UKCS), were deposited during semi-arid climatic conditions, within an active fault regime. The Triassic sequence represents fluvial alluvial sedimentation ranging from unconfined laterally extensive sheet flood deposits through to more confined small ribbon-like channel deposits. Geomorphologically stable areas demonstrate the development of palaeosols towards the upper regions of the Skagerrak Formation. Given the faunally barren nature and highly complex, fault-controlled sedimentation history, inter-well correlation of the Triassic interval of the field, has been relatively uncertain. The establishment of a well-constrained heavy mineralogical framework allowed a reservoir correlation scheme to be developed across eight of the ten wells present within the field. Sedimentological and petrophysical data were then integrated into this correlation scheme, to produce a high-resolution correlation across the Triassic interval of the field. The applicability of geochemistry to increase the resolution of the correlation scheme achieved across the Crawford Field Skagerrak Formation, was assessed through the analyses of samples on which, a detailed understanding of the heavy mineral assemblage and the sedimentology were known. Three distinct source terrains were identified for the Triassic interval of the Crawford Field. firstly, association 1 was sourced from a mid-Proterozoic hinterland, including the Western Gneiss Region (WGR) and the area to the south of this in Norway. This source terrain was, dominated by low-grade metasediments and higher-grade basic gneisses. Secondly, association 2 was sourced from a dominantly mid-Proterozoic hinterland containing subordinate Archaean and Caledonian age material, existing to the north around East Greenland. This source terrain was, dominated by high-grade metasediemtns and/or charnockites. Thirdly, association 3 was sourced from a mid-Proterozoic hinterland containing subordinate Caledonian age material and existed in the area around the WGR, Norway. This source terrain was, dominated by basic gneisses and rarer pyroxenites and peridotites.
|
|---|
