Reservoir Management in Selected Basin Floor Submarine Fan Reservoirs from the UKCS

Leonard, A., M. Bowman, and E. Jolley, BP-Amoco Ltd., Aberdeen, Scotland

Abstract

This paper reviews approaches to the exploitation of reserves from moderate to high net:gross submarine fan systems from the UK sector of the North Sea. Examples are given from the Forties, Magnus, and Andrew fields. It is shown how contrasting reservoir management approaches and experiences can be related to architectural elements of the different fan systems. The submarine fans range in age from Jurassic to Paleocene and the development schemes from platform drilled 'conventional' wells to geosteered h orizontal. These examples are broadly representative of other submarine fan reservoirs in the North Sea. Slope apron systems (e.g., Brae Fields) are excluded from this discussion.

The Forties and Andrew fields have reservoirs of Paleocene age (Forties and Andrew formations, respectively). The main reservoir in the Magnus Field is of Upper Jurassic age (Magnus Sandstone Member). All the reservoirs are, in summa ry terms, characterized by an upwards increase in depositional complexity and decreasing net:gross. This is caused by a change from amalgamated channelized sheet sands to channel and interchannel facies associations.

The Forties Field was initially developed using conventional near vertical production wells. Water flood was provided by water injection and a large regional aquifer. The production philosophy relied upon a stable rise of the OWC wit h progressive bottom up shut-off water producing zones. The philosophy was successful during production from the lower amalgamated sheet facies. However, late field life production relied upon accessing reserves in lower net:gross channel margin and inte rchannel facies--the higher net:gross channel facies having already been swept.

The remaining challenge for the Forties is the identification of unswept targets, largely in interchannel locations using 3D seismic and surveillance data.