John R. Underhill1
(1) The University of Edinburgh, Edinburgh, United Kingdom
ABSTRACT: Controls on the Genesis and Prospectivity of Paleogene Palaeogeomorphic Traps, East Shetland Platform, UK North Sea
A seismic stratigraphic interpretation of the Bressay area of the East Shetland Platform demonstrates the key role that fluctuations in relative sea-level had in the development and evolution of Paleogene deposition in proximal parts of the Viking Graben. Relative sea-level fall, probably driven by igneous underplating, enabled a Late Palaeocene-Early Eocene coarsening-up deltaic system to initially prograde and offlap as part of a forced regressive wedge. Coeval and subsequent erosion led to deep (>250m) incision of the delta and formation of a significant drainage system consisting initially of a dendritic incised valley network and a major, deep, low sinuosity channel, all of which fed sediment into distal parts of the basin. Structural relief on the surface that incised the delta together with either the onlapping, fine-grained tuffaceous valley fill or compactional drape above the coarse axial fill of the main low-sinuosity channel system combine to form good reservoir-seal pairs in two, distinctive and mutually exclusive palaeogeomorphic play types. A third closure exists associated with activity on a prominent reverse fault that appears to have initiated in response to rejuvenation of the Bressay Granite. Present-day hydrocarbon charge from the basin and the occurrence of heavy oil and gas in both of the subtle stratigraphic trap types and the independent structural closure has the potential to provide new exploration opportunities in the mature North Sea hydrocarbon province.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado