QDN盆地层序地层及生储盖组合分析

SEQUENCE STRATIGRAPHY AND SOURCE-RESERVOIR CAP ROCK ASSEMBLAGE OF QDN BASIN

周小鹰 魏魁生

Zhou Xiaoying Wei Kuisheng

QDN盆地是一个早期以裂陷为主,晚期以坳陷为主的拉张性盆地。可分为早期裂陷作用期、晚期裂后坳陷作用期两大演化期和5个演化阶段。根据盆地演化史和地层特征,早期裂陷作用期和晚期裂后坳陷期分别构成了超层序组TA和TB,在TA和TB中又可识别出5个二级层序和19个三级层序,并建立了年代层序地层格架。在本区的上、下两个生储盖组合中,下层生储盖组合有多个烃源层,始新统、崖城组湖相和海陆过渡相及各层序密集段皆为主要烃源岩,储集层主要由扇三角洲、砂滩、砂坝、前积楔和斜坡扇等组成;上层生储盖组合的烃源岩主要为梅山组密集段和莺歌海组外浅海深海泥质沉积,储集层主要为大陆斜坡部位的三角洲砂体;它们的区域性盖层为莺歌海组的厚层泥岩和梅山组深水泥质沉积;加之上、下两层生储盖组合烃源岩上覆有巨厚的深水泥质沉积,因此具有良好的油气前景。

QDN Basin is an extensional basin which fractured first and then depressed.The basin could be divided into 5 second order sequences and 19 third-order sequences.The basin's chronostratic framework was built according to basin's evolution history and formation characteristics.Two source reservoir cap rock assemblages were discovered in the basin.The lower assemblage consists of several source beds such as lake and transitional facies of the Eocene Series and Yacheng Formation;the reservoirs are mainly fan delta,sand beach,sand bars,foreset wedges and slope fans.The source rocks of the upper assemblage are the dense section of Meishan Formation,the shallow-abysmal argillaceous sediments of Yinggehai Formation;the reservoirs are deltaic sandbodies on continental slope.The regional cap rocks of the both are thick mudstone of the Yinggehai Formation and the abysmal ar gillaceous sediments of the Meishan Formation.It is considered that the basin possesses favourable hydrocarbon potential.

10.11743/ogg20000312