Abstract: Paleogene sandstone reservoir quality in the Huimin sag is mainly controlled by its compaction, carbonate cementation, dissolution and depositional environment. The evaluation to these factors suggests that: ①The porosity decreases by 8% to 9% per 1 000 m depth increasing due to compaction at shallow burial depth or during low diagenetic stage;②The influence of carbonate cementation is related to the diagenetic stages, greater influence is seen at higher diagenetic stages;③Dissolution plays an important role in controlling the reservoir quality. Secondary porosity from dissolution is up to 20%. However, the dissolution is mainly controlled by the regional tectonic setting and the planar position of the hydrocarbon producing depression, and the dissolution is relatively stronger in the south slope zone nearby the hydrocarbon producing depression and in the middle up-lift zone characterized by faults deve-lopment. Coarse, well sorted and low matrix sandstones often underwent heavy dissolution.

Key words: Huimin sag, reservoir quality, controlling factors