Janet Almond¹, Dave Taylor², Huw Williams³, Gary J. Hampson⁴, Howard D. Johnson⁴, Steve R. Taylor¹
(1) Shell UK Exploration & Production, Aberdeen, United Kingdom
(2) Esso Exploration & Production, Leatherhead, United Kingdom
(3) Reservoir Geology Consultants Ltd, Rhandirmwyn, United Kingdom
(4) Imperial College, London, United Kingdom

Abstract: Exploiting remaining oil in mature shoreface sandstone reservoirs: an example from the Brent Field, UK North Sea

Most major North Sea oil fields are now in advanced production decline.Maximising recovery and value in such reservoirs requires the integrationof (1) static and dynamic reservoir data, (2) quantitative data fromoutcrop analogues, (3) concepts for predicting high-resolution 3D reservoir architecture, and (4) 3D reservoirmodelling tools. We illustrate this with an example from thewave-dominated, shoreface/delta front sandstones of the Brent Group(Rannoch Formation) in the Brent Field. The Rannoch Formation was originally viewed as a simple coarsening upward, laterallyextensive and relatively homogeneous reservoir, with only minorthree-dimensional permeability heterogeneity. However, production haslagged behind that of other reservoirs during the field's 23-year production life, due to the water injection scheme havingpreferentially swept the overlying, higher permeability coastal barrier andvalley fill sandstones (Etive Formation). Detailed sedimentological studiesof core and wireline log data reveal subtle variations in bioturbation, mineralogy and mica content, whichdefine a composite succession of prograding shoreface deposits, includinggently dipping ( < 1 degree) clinoforms. Variations in clinoform geometryand spatial arrangement not only record evolving depositional processes, including syn-depositional tectoniccontrol on shoreline orientation, but also impart a strong control onpermeability anisotropy. High-resolution dynamic reservoir simulations havebeen undertaken, which preserve the clinoform-based geological model and its associated permeability anistropy.Results have helped define areas of bypassed oil that are now beingtargeted by infill wells, thereby contributing additional value to thecurrent late stage of oil development in the Brent Field.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana