【摘要】 荔湾凹陷是南海北部珠江口盆地超深水区的一个勘探新区,烃源岩是最重要的基础地质问题之一。通过荔湾凹陷地震反射特征分析,认为地震反射具有典型S型反射特征,为三角洲沉积体系。与相邻的白云凹陷类比研究,结合地震、钻井分析,提出荔湾凹陷恩平组三角洲体系是主力烃源岩发育带的新认识。以古生物分析为基础,从沉积环境入手,认为荔湾凹陷与白云凹陷恩平组沉积环境相似,为受限海相沉积环境。荔湾凹陷北部隆起提供物源,进入荔湾海相环境中,形成大规模三角洲体系。该三角洲体系与白云凹陷北坡恩平组三角洲体系具有相似的成煤环境,能够形成煤系烃源岩。同时受三角洲影响,在近三角洲体系的海相环境中,发育陆源海相烃源岩和海相烃源岩。通过地球化学分析认为煤系烃源岩、陆源海相烃源岩和海相烃源岩具有明显的不同,这3类烃源岩对于深水、超深水区域的勘探潜力具有很大影响。更多还原

【Abstract】 Liwan sag is a new exploration area in the ultra deep-water zone of Pearl River Mouth Basin,northern South China Sea,where the source rocks have arisen one of the most important geological problems.Based on the analysis of seismic data,we consider that Liwan sag is characterized by typical S-shaped seismic reflections and belongs to river delta depositional system.Through a comparative analysis with the adjacent Baiyun sag and combined with seismic and drilling data,we conclude that the delta system of Enping Formation is the main development zone of source rocks in Liwan sag.The results of paleontological analysis show that Liwan sag has a similar sedimentary environment as Baiyun sag,namely,a restricted marine depositional environment.The northern uplift of Liwan sag as the provenance enters into the Liwan marine environment,resulting in the formation of large-scale delta system.This delta system experiences a similar coal-forming environment as the delta system of Enping Formation on the northern slope of Baiyun sag,which can form coal-measure source rocks.As influenced by the delta system,terrigenous marine source rocks and marine source rocks are also developed in the adjacent marine environment.The results of geochemical analysis show that coal-measure source rocks,terrigenous marine source rocks,and marine source rocks are substantially different types of source rocks,all of which have significant implications for the exploration potential in deep-water to ultra deep-water areas.更多还原