--> Multidisciplinary Study Improves Reservoir Description of the Pickerill Gas Field (Rotliegendes), British Sector, Southern North Sea, by C. L. Vavra, D. A. Bell, E. A. Clerke, G. C. Gaynor, D. G. Peck, and G. A. Suellentrop; #90986 (1994).

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Abstract: Multidisciplinary Study Improves Reservoir Description of the Pickerill Gas Field (Rotliegendes), British Sector, Southern North Sea

Charles L. Vavra, D. A. Bell, E. A. Clerke, G. C. Gaynor, D. G. Peck, G. A. Suellentrop

Pickerill delineation and development encountered extremely variable reservoir quality and well productivity. Development was further complicated by uncertainties concerning locations of gas/water contacts, fluid saturation distribution and reservoir compartmentalization. A multidisciplinary study, combining sedimentology, zonation, pore-level description and petrophysical and engineering analysis was conducted to provide an integrated description and model.

Sedimentological and zonation studies indicated that nine lithofacies are present, including aeolian (dune and interdune), alluvial fan/braid plain facies, marine eolo-turbidite and slumped sandstones. These facies were grouped into four zones, which were divided into six layers to better represent heterogeneity in the reservoir simulation.

Pore-level studies indicate that the principal controls on reservoir quality are grain size and sorting (depositional process) and multiple diagenetic overprints. Additionally, the eastern and western portions of the field have undergone different amounts of diagenesis, which resulted in variations in porosity, permeability, capillarity and water saturation.

Four petrophysical rock types were identified from analysis of capillary pressure data. Differences between sonic and density log response were used to determine the occurrence and reservoir quality of these rock types. Saturation-height modeling of each petrophysical rock type provided estimates of free water level locations.

The sedimentological, pore-level and petrophysical descriptions provided the basis for building a reservoir model. Porosities derived from seismic attribute analysis were used to condition the interwell porosity distribution.

This work provided a more accurate representation of reservoir heterogeneity for full-field reservoir modeling, emphasizing that reservoir descriptions are improved through multidisciplinary team efforts.

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