--> ABSTRACT: Direct Gas Detection in the Rotliegendes Sandstone: A Potential New Opportunity for Exploration in the UK Southern Gas Basin, by Dr Chris D. Atkinson, Bruce VerWest, Graham Baker, and Peter O'Mara; #90906(2001)

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Dr Chris D. Atkinson1, Bruce VerWest2, Graham Baker3, Peter O'Mara4

(1) Petroleum Development Associates, London (UK), United Kingdom
(2) Veritas DGC, Houston, TX
(3) Humber Exploration Co, London (UK), United Kingdom
(4) Consultant Geologist, London (UK), United Kingdom

ABSTRACT: Direct Gas Detection in the Rotliegendes Sandstone: A Potential New Opportunity for Exploration in the UK Southern Gas Basin

With discovered reserves to date of 54 TCF of gas and cumulative production since 1967 of 34 TCF the UK Southern Gas Basin (SGB) is regarded as a truly great petroleum province. The main play, the Permian Rotliegendes Sandstone, is considered a mature exploration target, a fact reflected by the general reduction in new discovery reserves size through time as smaller and smaller prospects have become harder and harder to find. In the late 1980's increased use of 3D seismic data temporarily reversed this trend as more structurally subtle Rotliegendes objectives were defined and drilled with success. In the 1990's the increasing use of pre-stack time and depth migrated data, with improved definition of complex structural features and improved spatial positioning, provided a similar step change in exploration success. The future for continued success in the SGB may rely on a potentially more exciting innovation that utilises careful pre-stack amplitude analysis and accurate well calibration to provide a tool to enable direct detection of gas within the Rotliegendes. This technology becomes especially relevant in those areas of the basin where very low relief (< 40 meters) but areally extensive base Zechstein closures are known to exist or within fields with undrained, fault sealed, compartments. In these areas a combination of accurate depth mapping of the structure coupled with the overlay of a calibrated amplitude response and 3D visualisation techniques, reveals the presence of several potentially large (up to 600 bcf), low risk, Rotliegendes targets. Successful drilling of these features could lead to a dramatic increase in discovery sizes in the basin and a new lease of life for the Rotliegendes fairway.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado