珠江口盆地惠州凹陷迁移型层序特征及其意义

Migrated Sequence Stratigraphic Architecture and Its Geological Significance in Huizhou Depression,Pearl River Mouth Basin

迁移型层序是陆相湖盆中一种特殊的层序构型,但是其特征以及主控因素尚不清楚.通过对珠江口盆地惠州凹陷文昌组层序地层学研究,发现下文昌组三级层序PSQ1-PSQ4主要发育在凹陷南部,上文昌组三级层序PSQ5-PSQ7主要发育在凹陷北部;三级层序PSQ1-PSQ7逐渐由南东向北西发生跨洼陷迁移.这种迁移型层序是由幕式构造活动差异性造成的,在裂陷IA幕,惠州凹陷南部控凹断裂活动强度大,发育以下文昌组为主的T型层序构型;在裂陷IB幕,北部断裂活动加强,南部的断裂活动减弱,造成沉积、沉降中心迁移到惠州凹陷北部,发育以上文昌组为主的H型层序构型.迁移型层序及其控制下的砂体和烃源岩在侧向迁移、叠加过程中,更利于生、储、盖等油气成藏要素的有效配置,形成多区块、多层段油气藏组合。

Migrated sequence stratigraphic architecture represents a special type in continental lacustrine rift basin.However,its characteristics and main controlling factors are unclear yet.Lower Wenchang Formation（PSQ1-PSQ4）is mainly distributed at south of Huizhou depression,while upper Wenchang Formation（PSQ5-PSQ7）is distributed at northern part.It is found in this study that sequences in Wenchang Formation migrate from southeast to northwest across Huizhou depression.Migration of sequence is generally caused by different stages of episodic tectonic activity.In rifted stage IA,tectonic activities of southern depression strengthen largely and sequences configuration show as Type T,which mostly develops lower Wenchang Formation.However,as for rifted stage IB,northern tectonic activities become stronger,which results in migration of depocenter and subsidence center from north to south.And sequences configuration show as Type H which mainly develops upper Wenchang Formation.Moreover,migration of sequence stratigraphic unit generates multi-block along the direction of migration and also a combination of multi-stage oil and gas reservoirs,which are all of great potential for exploration.