--> High Resolution Sequence Stratigraphic Reappraisal of the Upper Jurassic Fulmar Sands Reservoirs, North Sea, Central Graben, by J. Howell and S. Flint; #90986 (1994).

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Abstract: High Resolution Sequence Stratigraphic Reappraisal of the Upper Jurassic Fulmar Sands Reservoirs, North Sea, Central Graben

John Howell, S. Flint

Variably thick, monotonous successions of shallow marine bioturbated sandstones characteristics the Upper Jurassic Fulmar Formation of the United Kingdom Central Graben. These were deposited within a complex rift basin, the palaeogeography of which was controlled by both extensional and salt tectonics. The basin geometry combined with second-order regional transgression resulted in a series of laterally restricted sandbodies which progressively onlap the basin margins.

Detailed re-logging of core material from eighteen wells integrated with all the released data has led to a reappraisal of the succession. Sandbody age and distribution have been delineated within a third-order, biostratigraphically calibrated, flooding surface framework which has enabled the application of facies, high resolution, "unconformity bound" sequence stratigraphically analysis.

Improved understanding of the depositional system and a new sedimentological model has permitted the recognition of subtle sequence elements within otherwise uniform successions. A series of third-order composite sequence have been identified and can be correlated.

The internal architecture of these third order cycles varies greatly between individual fault blocks and a range of composite and simple sequences were deposited over comparable time periods. This range includes, third order composite sequences with fourth-order high frequency sequences; third order composite sequences in which downshift surfaces are only present during lowstand and late highstand times, and, simple third order sequences which lack any high frequency component. Sequence stratigraphy analysis has resulted in greatly improved understanding of reservoir anatomy on a regional and field scale, and has resulted in improved understanding of the area.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994