珠江口盆地惠州25转换带文昌组五段早期低位体系域源—渠—汇耦合关系及勘探潜力探讨

基于地震和钻井资料,利用层序地层学及源—渠—汇分析技术,探讨了惠州25转换带文五段早期低位体系域发育背景及源—渠—汇沉积充填模式,并对勘探潜力进行分析。结果表明:1）惠州25转换带文五段具有三级层序属性,依据初始湖泛面和最大湖泛面特征,将文五段进一步划分出低位体系域和湖侵体系域；2）综合分析文五段早期低位体系域沉积的源—渠—汇耦合关系,将低位体系域划分为惠州5-4沉积区、惠州5-7A沉积区和惠州5-7B沉积区:惠州5-4沉积区低位体系域规模最大,以文六段滩坝相砂体和辫状河三角洲前缘亚相砂体为母岩,经3号沟谷搬运入湖形成辫状河三角洲前缘沉积,具有高成分成熟度和结构成熟度特征；惠州5-7A沉积区低位体系域规模最小,以文六段辫状河三角洲前缘亚相砂体提供母岩,搬运入湖形成辫状河三角洲前缘沉积；惠州5-7B沉积区低位体系域规模中等,以文六段辫状河三角洲平原、前缘亚相砂体和惠西低凸起西段花岗岩母岩混合物源供源,分别经2号和1号沟谷搬运入湖形成辫状河三角洲前缘沉积,其成分成熟度和结构成熟度低于惠州5-7A区和惠州5-4区；3）惠州5-4沉积区低位体系域砂体规模大、储层优、盖层封堵条件优越,且相对于惠州5-7区低位体系域砂体具有旁生侧储、近源成藏优势,是下一步寻求隐蔽油藏有利勘探目标。

Exploration Potential and Source?ditch?sink Characteristics of the Lowstand System Tract in the Early Sedimentary Stage of the 5th Member of the Wenchang Formation,Huizhou 25 Transfer Zone

Based on seismic and drilled data, this study analyzed the sedimentary model and the exploration potential of the lowstand system tract in the early sedimentary stage of the 5th member of Wenchang Formation in the Huizhou 25 transfer zone,using sequence stratigraphy and source-ditch-sink analysis technologies. The following results were noted. （1） Based on the initial and maximum flooding surface, a lowstand system tract and a transgressive system tract have been identified. （2） The lowstand system tract was divided into the Huizhou 5-4, 5-7A and 5-7B sedimentary areas from source?ditch?sink characteristics. The Huizhou 5-4 area is the largest, its’ the parent rock was a beach bar facies sand body and braided river delta front subfacies sand body in the 6th member of the Wenchang Formation, through No. 3 valley to form braided river delta front sediments of high compositional and structural maturity. The Huizhou 5-7A lowstand system tract is the smallest sedimentary area. Its parent rock was the subfacies sand body of a braided river delta front in the 6th member of the Wenchang Formation, which was transported into the lake to form a braided river delta front. The 5-7B lowstand system tract covers a medium-sized area. Its source was a mixture of braided river delta plain and front subfacies sand body of the 6th member of Wenchang Formation transported into the lake through No.2 valley, together with granite of the Huixi low uplift transported into the lake through No.1 valley, to form braided river delta front deposits. It has lower compositional and structural maturity than either the Huizhou 5-7A or 5-4 areas. （3） Compared with the Huizhou 5?7A and B areas,the Huizhou 5?4 lowstand system tract sand body has the largest scale,excellent reservoir and sealing condition,good source?to?reservoir formation. So it is a favorable exploration target for a lithological reservoir.