Gregor Maxwell, Adrian Hartley, John Crane
Tidally dominated sections from the Middle Jurassic Beryl Formation of the Beryl Field, Viking Graben (UKCS) were deposited during rapid changes in relative sea level. High density well coverage in this key producing interval has allowed the construction of an integrated high resolution sequence stratigraphic scheme based on sedimentological, ichnofaunal, wireline, biostratigraphic and engineering data. From this database a number of high resolution sequences in the Bajocian-Bathonian Beryl Formation have been identified composed of interbedded sandstones, siltstones and mudstones. These sediments formed tidally-influenced deltas and estuaries deposited in actively subsiding half-grabens during regionally extensive base-level changes.
For reservoir management purposes, the formation has been split into 5 units. The thickest interval, Unit 3, is considered here. In the northern part of the Beryl Field, Unit 3 is bounded above and below by regionally extensive, biostratigraphically correlatable mudstones. In this area it can be sub-divided into up to 8 sub-units which more accurately represent the flow units. Sub-units represent high resolution depositional sequences and are distinguished by thin, extensive flooding surfaces which in many cases form traceable pressure barriers across tilted fault blocks throughout the field.
This integrated approach using varied geologic and engineering techniques has resulted in a detailed sedimentological and high resolution sequence stratigraphic model. Zoning this field which had a complex depositional and production history into workable reservoir units has had a positive impact on reservoir management through improved reservoir simulation model predictions, identification of recompletion opportunities and infill drilling strategy.
AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela