Improved Reservoir Management by Integrated Study: Cormorant Field, Block 1

Abstract

ABSTRACT The Cormorant field, in the East Shetland Basin of the Northern North Sea, consists of four oil accumulations in the productive Brent Group. Block I, the central structure, is a 15 km long, north-south trending and westerly tilted fault block with crestal erosion. To evaluate future development options and to provide a realistic forecasting and monitoring tool, a multi-disciplinary Petroleum Engineering study was carried out. A complete geological and petrophysical review was undertaken as an integral part of the study. This included a reservoir geological description of the main reservoir units, an analysis of the sealing capacity of the internal faults, and permeability prediction using multi-linear regression. The results of the review formed the basis for the detailed Block I 3D reservoir simulation model. History matching identified the key reservoir parameters responsible for the observed pressure and water cut trends. These were the sealing capacities of the faults, the transmissibility between reservoir units, and the differing sedimentary fades (channel, barrier, interchannel, mouthbar, lagoonal beach) in the Etive and Lower Ness reservoir units. The facies variations were found to exercise considerable control on permeability trends and fluid displacement efficiency. Their proper description proved fundamental. The model has been used to evaluate alternative development options. These have led to the formulation of a new development plan that should increase ultimate recovery in the order of 10% (20 MMstb) [3.2 × 106 m3].