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Book Chapter

The Johnston Gas Field, Blocks 43/26a, 43/27a, UK Southern North Sea

By
David E. Lawton
David E. Lawton
BHP Billitron Petroleum Ltd, Neathouse Place, London, SW.1V 1LN, UK
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Paul P. Roberson
Paul P. Roberson
BHP Billitron Petroleum Ltd, Neathouse Place, London, SW.1V 1LN, UK
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Published:
January 01, 2003

Abstract

The Johnston Field is a dry gas accumulation located within blocks 43/26a and 43/27a of the UK Southern North Sea. The discovery well was drilled in 1990 and after the drilling of one appraisal well in 1991, a development plan was submitted and approved in 1993. Initially two development wells were drilled from a four slot sub-sea template, with commercial production commencing in October 1994. A further horizontal development well was added to the field in 1997.

The field has a structural trap, fault bounded to the SW and dip-closed to the north, east and south. This field geometry has been established using high quality 3D seismic data, enhanced by seismic attribute analysis. The sandstone reservoir interval consists of the Early Permian, Lower Leman Sandstone Formation of the Upper Rotliegend Group. This reservoir consists of a series of interbedded aeolian dune, fluvial, and clastic sabkha lithofacies. The quality of the reservoir is variable and is principally controlled by the distribution of the various lithofacies. The top seal and fault bounding side seal are provided by the overlying claystone of the Silverpit Shale Formation and the evaporite dominated Zechstein Supergroup.

The field has been developed using a phased development plan, with the acquisition of a 3D seismic survey allowing for the optimized drilling of a high deliverability horizontal well.

Current mapped gas initially-in-place estimates for the field are between 360 and 403 BCF, with an estimated recovery factor of between 60 and 75%.

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Contents

Geological Society, London, Memoirs

United Kingdom Oil and Gas Fields Commemorative Millennium Volume

J. G. Gluyas
J. G. Gluyas
Acorn Oil Gas Ltd, Staines, Middlesex, UK
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H. M. Hichens
H. M. Hichens
Oil and Gas Directorate, London, UK
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Geological Society of London
Volume
20
ISBN electronic:
9781862393950
Publication date:
January 01, 2003

GeoRef

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