RESERVOIR DISTRIBUTION AND DIAGENESIS IN THE NORTHERN NORTH SEA BASIN

Reservoirs in the northern North Sea Basin range from fractured basement to Eocene deposits. There are five sets of main reservoirs:① the Permian Rottiegeudes aeolian and/or alluvial sandstones;②the Triassic fluvial sandstone;③the Middle and Lower Jurassic fluvial, deltaic and marginal marine sandstone; ④the Upper Jurassic shallow marine and deep marine turbidite sandstone and conglomerate; ⑤the Upper Cretaceous- Lower Paleocene chalk and Paleocene deep-sea turbidite fan sandstones. It is found that the Paleocene- Eocene sandstone is weak in diagenesis and permeability becomes lower under 3100 m. The dissolution of K-feldspar is a major factor influencing diagenesis and permeability in the shallower part. Then illite becomes the main factor below about 3700 m, and secondary quartz plays a major role in the sequence below 4000 m. Oil and gas accumulation depends on the distribution pattern of reservoirs.