【摘要】 白云凹陷北坡地区是珠江口盆地最有利的油气勘探区域之一,其层序地层学特点表现为沉积受控于特殊的古地理位置——陆架坡折带。从距今21 Ma至今,陆架坡折带位置基本保持在该区附近,在低海面时期发育了大量低位体系域沉积砂岩体,具备优先捕获油气的有利条件。为此,在前人研究的基础上,利用钻井、地震资料,结合各种层序界面特征,重新确定了该区新近系珠江组下段SB23.8、SB21等2个层序界面,划分出2个三级层序、5个四级层序地层单元,从而建立起等时地层格架;之后,对该区近3 000 km2三维地震SB21.0层序界面之上的陆架坡折点进行了识别和追踪,确定出陆架坡折带的分布范围,识别出其低位体系域时期所分布的主要沉积地质体:主要有低位楔或陆架边缘三角洲、水道充填、低位扇等3种类型,并对其特征及展布规律进行了详细描述。结论认为:上述陆架坡折带具备有利的油气成藏条件,充足的油气源,优越的储集条件,良好的运聚匹配条件和保存条件以及晚期成藏特征等,同时,由于其上的砂岩体具有良好的形成岩性—地层圈闭条件,因此,该陆架坡折带极具油气勘探价值。更多还原

【Abstract】 The north slope of the Baiyun Depression is one of the most favorable areas for gas exploration in the Pear River Mouth Basin,where,from the perspective of the sequence stratigraphy,the deposition is controlled by the special palaeogeographic location,i.e.shelf break zone.This shelf break zone has been kept within or near the study area since 21 million years ago and has accumulated a large amount of the lowstand system tract(LST) sandbodies which are favorable for capturing hydrocarbons.Based on the previous studies and in combination with drilling and seismic data as well as features of various sequence boundaries,two sequence boundaries(SB23.8 and SB21) were redefined in the lower member of the Neogene Zhujiang Formation,2 third-order sequences and 5 fourth-order sequences were recognized,and an isochronous stratigraphic framework was established.Through identifying and tracing shelf break point above the SB21.0 sequence boundary within the 3D acreage of 3000 km2 in the study area,we delineated the distribution area of this shelf break zone and recognized the major sedimentary bodies formed during LST,including lowstand wedge or delta on shelf margin,channel fill and lowstand fan,and describe in detail their features and distribution patterns.It is believed that this shelf break zone has favorable conditions for hydrocarbon accumulation,sufficient hydrocarbon sources,quality reservoirs,good timing of hydrocarbon migration and accumulation,supreme sealing conditions,and late pooling.Moreover,the sandbodies above are favorable for the formation of lithologic-stratigraphic traps.All these show that this study area has a great gas exploration potential.更多还原