WRIGLEY, RICHARD, British Gas, Reading, Berkshire, England; and DAVID PHILLING and ANGELA MELVIN, PM GEOS, Aberdeen, Scotland

ABSTRACT: Rotliegende Group Event Stratigraphy, Quadrants 42 and 47, Southern North Sea

The Easington Catchment Area is located in United Kingdom continental shelf Quadrants 42 and 47, 40 km offshore north Humberside, in the Southern North Sea basin. The area is located on the northern margin of the Rotliegende play fairway, where reservoir development, facies and quality is highly variable.

Conventional lithostratigraphic nomenclature for the Lower Permian of the United Kingdom continental shelf Southern North Sea basin proposes a twofold subdivision of the Rotliegende Group with the boundary between the Leman Sandstone Formation (LSF) and the Silverpit Claystone Formation (SCF), often portrayed on wireline logs as a sharp contact. Analysis of core and log data from wells in the area demonstrates that the boundary is diachronous. Given the complexity of the depositional environment, the adoption of a sharp boundary is potentially misleading when correlating wells and predicting reservoir trends.

This paper describes the development of a tectonic and climatically controlled event stratigraphy for the Rotliegende Group. In the absence of biostratigraphic data, sabkha and lacustrine intercalations have been interpreted as isochronous markers which equate to maximum flooding surfaces in marine sequences. Where sabkha intercalations are absent, laterally equivalent sand sheet packages or fluvial events have been used for correlation.

A series of paleogeographic models and well correlations have been produced which are highly predictive in terms of facies distribution. The results of the study also highlight the diachronous nature of the LSF and SCF and the control of Carboniferous paleorelief on facies and thickness variations in the Rotliegende Group.

The results of the study have been used to predict Rotliegende Group facies and reservoir quality on a regional basis, a critical play element for successful exploration in this mature area.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.