John R. Underhill1, John Argent2, Simon Stewart3, Paul Green4
(1) The University of Edinburgh, Edinburgh, United Kingdom
(2) Amerada Hess, London, United Kingdom
(3) Amerada Hess, United Kingdom
(4) Geotrack International, Melborne, Australia
ABSTRACT: Role of Strain Partitioning and Fault Reactivation during Basin Inversion: Implications for seal breach and hydrocarbon leakage in the North Sea Basin
Integration of regional seismic interpretation, sonic velocity, vitrinite reflectance and apatite fission track (AFTA) studies in the North Sea Basin have demonstrated that western areas of the Moray Firth rift arm experienced uplift during the Cenozoic. Although the results have previously been considered to be consistent with a regional, gradual increase in uplift, well-calibrated seismic interpretations of regional 2-D and local 3-D surveys from the Inner Moray Firth demonstrate that current understanding is over-simplified. Instead, it can now be shown that highly-localised, differential uplift characterised the basin, the effects of which are primarily expressed through the extensional reactivation of Late Jurassic rift structures. Whilst throws on the rejuvenated normal faults are usually in the range of 100-300m (e.g. the Smith Bank Fault and along the Central Ridge), throws are known to exceed 1km either side of the Sinclair Horst, a pronounced E-W trending ridge in the basin. Reactivation of the faults created a significant seal risk to valid hydrocarbon prospects, several of which appear to have been breached as a result. The best known exception is the Beatrice Field, the bounding fault to which remained entirely dormant during Cenozoic events. The results from the Moray Firth suggest that differential uplift due to strain partitioning should be expected in other inverted sedimentary basins.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado