SCALES OF PERMEABILITY HETEROGENEITY WITHIN THE BRENT GROUP

Abstract

A selection of Brent Group reservoir sequences from the Murchison field were chosen to study the nature of permeability variation within the Brent Group, with particular emphasis on the Etive Formation, which forms one of the main reservoirs in the field.Preliminary core examination of potential permeability barriers, as identified using wireline log response, has indicated that permeability heterogeneities can be placed into a five‐fold hierarchy. Permeability heterogeneities resulting from depositional or syndepositional processes comprise the first four orders of heterogeneity and include formations, facies transitions, bedding surfaces and laminations. Permeability heterogeneities which are the product of diagenetic processes are classified as fifth‐order heteorgeneities.Two major types of permeability barrier have been identified in core and on wireline logs within the Etive Formation. They include permeability heterogeneities associated with a transition between the two major facies associations (tidal channel and beach/foreshore sandstones); and heterogeneities associated with the development of inactive channel‐fill sandstones and siltstones within the tidal‐channel facies association.A detailed sedimentological model has been developed which demonstrates the complexity of reservoir zonation in the Etive Formation within the Murchison field.