珠江口盆地阳江凹陷东部地区断控成藏条件

阳江凹陷东部地区是近年来珠江口盆地(东部)的热点探区,过去四十余年受限于钻井数量、地震资料品质和覆盖范围,缺少对断裂特征及控藏作用的系统解剖。本文在覆盖全区的高品质三维地震资料基础上,对阳江凹陷东部的断裂系统进行解剖,并探讨断裂对沉积充填、烃源展布、圈闭发育、油气运聚与保存的控制作用。研究表明,阳江凹陷东部的断陷格局具有典型的古近系和新近系上下双层结构,组成断裂可分为裂陷期断裂系统、拗陷期断裂系统和长期活动断裂系统。阳江凹陷东部的洼陷结构受长期活动断裂和裂陷期断裂共同控制,断裂的差异活动控制了沉积体系特别是辫状河三角洲和半深湖相烃源岩的展布。三套断裂系统历经三期构造演化过程,控制形成了三种不同类型的圈闭,主导了阳江凹陷东部主要圈闭的形成与分布。此外,断裂还控制油气运移和保存条件的差异性:一级和二级油源断裂主导了新近纪油气的垂向运移;NW向张扭断裂侧向封堵能力强,控制了油气的富集程度。

Fault-controlled Hydrocarbon Accumulation in the Eastern Yangjiang Sag,Pearl River Mouth Basin

After 40 years of exploration in the eastern Yangjiang Sag of the Pearl River Mouth Basin,a breakthrough had finally been made in 2018,however,the reservoir-forming conditions are still unclear.A systematic investigation was carried out to delineate the fault controls on the distribution,trap and transportation of hydrocarbon.This study shows that the eastern Yangjiang Sag consists of the Neogene upper layer and Paleogene lower layer,and the faults in the sag can be divided into three types:the syn-rift,the depression-and the long-term-fault systems.The depression structure in the eastern Yangjiang Sag is controlled by both the long-term active faults and the early-stage syn-rift faults,and their differential activities controlled the distribution of the sedimentary systems,especially those of the braided river delta and middle-deep lacustrine source rocks.These faults controlled the formation and distribution of the main traps in the eastern Yangjiang Sag.These faults experienced three stages of evolution and controlled the formation of three different types of traps,and therefore,different hydrocarbon migration and preservation.The primary and secondary oil-source-linked faults dominated the vertical migration of the Neogene oil and gas,and the NW-trending tensional and torsional faults are favorable for lateral sealing and enrichment of oil and gas.