东海盆地西湖凹陷黄岩地区油气成藏主控因素及成藏模式

Main controlling factors and reservoir forming models of oil and gas reservoirs in Huangyan area,Xihu Sag,East China Sea Basin

西湖凹陷西次凹黄岩地区渐新统花港组油气资源丰富,是东海陆架盆地勘探开发重要领域,但油气成藏机理复杂。为厘清西次凹花港组油气成藏过程,笔者等通过薄片观察、扫描电镜、流体包裹体、显微测温等实验分析,结合构造演化、埋藏史等,开展了生储盖、成藏期次及成藏过程研究。结果表明,花港组砂岩储层具有良好的储集条件,始新统平湖组发育有效的烃源岩,还具有良好的圈闭条件和保存条件。早期发育的断裂,延深至下部平湖组烃源岩层内,可以作为良好的运移通道,深部超压的发育为油气运移也提供一定的动力。因此建立了“垂向叠置”成藏模式,说明西湖凹陷深层低渗—特低渗致密岩性—构造复合油气藏和深部地层存在异常压力系统内的油气藏的具有良好的勘探前景。

The Oligocene Huagang Formation in the Huangyan area of the West Subsag,Xihu Sag(some one calls the Xihu Sag as Xihu Depression),East China Sea Basin,is riched in oil and gas resources,which is an important area for exploration and development in the East China Sea shelf basin.However,the mechanism of oil and gas accumulation is complex.In order to clarify the process of oil and gas accumulation of the Huagang Formation in the West Subsag,this paper conducts research on the source reservoir cap,reservoir formation stages,and reservoir formation process through thin section observation,scanning electron microscopy,fluid inclusions,microscopic thermometry,and other experimental analysis,combined with structural evolution and burial history.The results show that the sandstone reservoir of the Huagang Formation has good reservoir conditions,while the Eocene Pinghu Formation develops effective source rocks,and also has good trap and preservation conditions.The early developed faults extend deep into the source rock of the lower Pinghu Formation and can serve as good migration channels.The development of deep overpressure also provides a certain driving force for oil and gas migration.Therefore,a“vertical superimposed”reservoir formation model has been established,indicating that the deep low permeability to ultralow permeability tight lithologic structural composite oil and gas reservoirs in the Xihu Sag and the oil and gas reservoirs in the deep formation with abnormal pressure systems have good exploration prospects.