Greig Cowan and Joanna Bradney
Regional diagenetic controls on reservoir properties in the Millom accumulation; implications for field development (in Petroleum geology of the Irish Sea and adjacent areas)
Geological Society Special Publications (1997), 124 373-386

Abstract:
The Millom accumulation comprises two dip-closed culminations situated down-flank of the 1 TCF North Morecambe Field. The depositional environments encountered in the Millom area are similar to those in the North Morecambe area and they share a common depositional layering. However, porosity and permeability are low compared to the Morecambe Fields. Although the presence of permeability reducing platy illite throughout the reservoir can explain the reduced permeabilities in the area, it does not account for the reduced porosity. The abundance of mineral cements (quartz and carbonates) increases rapidly away from the crest of the North Morecambe structure, down-dip towards the Millom area. The migration history of fluids outwards from the deeper parts of the basin is preserved by the cement distributions observed in the Morecambe-Millom area. Porosity in North Morecambe is preserved by an early hydrocarbon charge. The Millom structure had not formed during early hydrocarbon migration and was exposed to mineralizing fluids moving from the Keys Basin to the north. Both structures were filled with the present gas charge during late Cretaceous/early Tertiary gas migration. Poor reservoir properties, especially K _v , renders Millom unsuitable for development by horizontal wells.