The Windermere Gas Field, Blocks 49/9b, 49/4a, UK Southern North Sea
R. J. Bailey, J. E. Clever, 2003. "The Windermere Gas Field, Blocks 49/9b, 49/4a, UK Southern North Sea", United Kingdom Oil and Gas Fields Commemorative Millennium Volume, J. G. Gluyas, H. M. Hichens
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The Windermere Field, in the central area of the Southern North Sea gas province, exploits a variant of the Rotliegend-Leman Sandstone gas play. A thin, basal aeolian sandstone is top-sealed by lacustrine Silverpit Formation, claystones and sourced by the underlying Westphalian Coal Measures. Since the reservoir unit has no mappable seismic expression, trap definition depends on depth mapping the Base Zechstein and adding the appropriate Silverpit Formation isochore. The trap is a simple, uncompartmentalized, anticlinal feature, lying largely within Block 49/9b. The 49/9b-2 discovery well (1989) penetrated the crest of the feature and the 49/9b-4 appraisal well (1994-1995) was drilled down-plunge to the SE. Both encountered some 20 m of predominantly aeolian-dune sandstone overlying the Base Permian Unconformity. This reservoir flowed dry gas at rates of 0.8-1.0 MMm3/d. The GWC was not penetrated; however RFT pressure projections suggest that it lies at around 3528 m. Stochastic estimates suggested Leman Sandstone GIIP of 2.8 bcm (104 BCF). The field’s two- well development is tied back to a minimum facilities platform with export to Den Helder, via the Markham ST-1 platform. On commissioning, in August 1997, the two-wells flowed at 1.8 MMm3/day. By January 1999, 0.682 bcm of the originally- estimated 2.3 bcm gas reserve had been produced.