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Richard Evans1,
J. A. Cartwright2,
H. D. Johnson1,
M. Hartung3,
S. Kelly3,
N. A. Lee1,
L. Lonergan1
(1) T.H. Huxley School, Imperial College, London, United Kingdom
(2) Cardiff University, Cardiff, United Kingdom
(3) Shell U.K. Exploration and Production Ltd, Aberdeen, United Kingdom
Abstract: Impact of structural framework on the geometry and distribution of the Tay Fan, U.K. Central North Sea
The Eocene Tay Fan is a relatively small (60 km2) deep-water fan, which is situated in the Central North Sea, immediately above the western edge of the underlying Mesozoic Central Graben. An extensive well and seismic database provides an opportunity to reconstruct the fan?s depositional geometries and internal reservoir architecture throughout it's full extent, and to assess the geological controls on it's evolution.
The Tay Fan has been cited as a typical ancient deep-water fan, characterised by a predictable network of channels and fan lobes. However, this is not always supported by the complex and, in places, chaotic internal relationships revealed by the 3D seismic data. Instead, these data suggest a potentially more complex interpretation, in which tectonically-induced basin floor topography influenced primary fan geometry, internal architecture and spatial variability. Pre-existing N-S and NNW-SSE trending shear zones relating to underlying Mesozoic faults controlled the fundamental basin configuration and may have influenced sediment transport pathways. Superimposed on this structural control is modification of sandbodies by differential compaction, re-mobilization (de-watering) and local gravitational sliding. Further structural overprinting is characterised by (1) radial fault networks, associated with halokinesis, and (2) polygonal faults, within overlying sealing mudstones, which may, in places, disrupt reservoir continuity at Top Tay level. The influence of these structural features on depositional processes and reservoir continuity, particularly at a field- and prospect-scale remains difficult to assess. However, earlier models of high reservoir homogeneity and continuity may have been an oversimplification, which could impact on field development activity.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana