The Scott Field, Blocks 15/21a, 15/22, UK North Sea
Simon Guscott, Ken Russell, Andrew Thickpenny, Robert Poddubiuk, 2003. "The Scott Field, Blocks 15/21a, 15/22, UK North Sea", United Kingdom Oil and Gas Fields Commemorative Millennium Volume, J. G. Gluyas, H. M. Hichens
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The Scott Field straddles Blocks 15/21 and 15/22 on the southern flanks of the Witch Ground Graben in the Outer Moray Firth Basin, UKCS. The oil field is developed in the highly productive Upper Jurassic Humber Group sandstones of Oxfordian to Kimmeridgian age. The field was discovered in 1983, sanctioned in 1990, and produced first oil in 1993.
The field structure, effectively a large southwards tilted fault block, is compartmentalized into a series of four main pressure isolated fault blocks by mid to late Jurassic faulting. The Kimmeridge Clay Formation provides both the top seal and the source of the trapped hydrocarbons. Fluid contact, overpressure and compositional trends suggest that the trap was filled primarily from the north. Some trap-defining faults were already active during the deposition of the reservoir intervals. Well data indicate that the development of accommodation space was technically controlled during this period, with subsidence occurring more rapidly in the western areas of the field.
The Scott Field reservoir consists of two major sand packages, the Scott Sandstone Member and the Piper Sandstone Member, bounded above and below by marine flooding surfaces. The late Oxfordian Scott Sandstone Member consists of a westwards prograding marine shoreface sandstone overlain by aggradational and retrogradational back-barrier deposits. Above this, the Mid Shale is a regionally extensive flooding event separating the Scott Sandstone Member from the overlying Piper Sandstone Member. The early Kimmeridgian Piper Sandstone Member consists of stacked mass flow sandstones, overlain by a shoreface/back-barrier system. Lateral facies changes and thickness variations significantly affect reservoir distribution in both Scott and Piper intervals.
The best reservoir quality occurs within the coarsest grained, highest energy facies, particularly the shoreface and proximal washover deposits. At the crest of the field, 10400 ft TVDss, multi-Darcy permeabilities and porosities of 20% are common. However, reservoir quality declines progressively downflank due to increased quartz cementation and compaction.
The Scott Field currently produces from 23 wells supported by 20 water injectors. Current modelling is aimed at targeting bypassed oil to increase ultimate recovery. The field has presently produced 300 MMSTB of oil from forecast reserves of 440 MMSTB with an estimated ultimate recovery factor of c. 46%.
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Memoir 20 is the most comprehensive reference work on the UK’s oil and gas fields available. It updates and substantially extends Memoir 14 (1991), United Kingdom 0il and Gas Fields, one of the Geological Society’s best-selling books. This new edition contains updates on many of the ageing giant fields, as well as entries for fields either undiscovered or undeveloped when Memoir 14 was published.
The book is divided into nine parts covering the major petroleum provinces both offshore and onshore United Kingdom, from the Gas Basin in the southern North Sea to the Viking Graben in the northern North Sea, from the Atlantic Frontier to the Irish Sea and from the Wessex Basin to the East Midlands. Each part contains a reference map showing field locations. The introductory chapters reveal the stories behind the major plays and discoveries therein, and their tectonic and stratigraphic framework. There are two appendices: tabulated field data and a comprehensive list for all of the UK's 300+ oil and gas fields.