张扭性断裂带的生长过程与油气穿断运移评价--以珠江口盆地恩平凹陷为例

张扭性断裂带是珠江口盆地普遍发育的断裂类型,是沟通深部烃源岩与中浅部储层的关键,是油气运移、聚集分析的核心环节。以恩平凹陷E18雁列式断裂带为例,基于三维地震、测井和钻井地质数据,采用T-x图、T-z图及活动速率图方法,恢复E18断裂带的生长过程及分段特征,并依据岩性对接、泥岩涂抹、断层岩发育特征,评价油气穿断裂侧向运移的条件。结果表明,E18断裂带在裂陷期是单一断裂,裂后期表现为雁列形态,活动过程包含4个阶段,活动中心由西部转移至中部,大规模生排烃时期最大活动速率可达20m/Ma,形成2个良好的垂向疏导中心,分段特征明显;油气容易穿透E18断裂带珠海组和韩江组下段2套地层发生侧向运移,并且连接部位是最有利于油气穿断运移的部位。E18断裂带生长过程和油气穿断侧向运移的评价有助于认识E18a油田和E18f油田的成藏过程。

GROWTH PROCESS OF TRANSTENSIONAL FAULTS AND ITS CONTRIBUTION TO HYDROCARBON LATERAL MIGRATION ACROSS THE FAULTS:A CASE FROM ENPING SAG OF PEARL RIVER MOUTH BASIN

Transtensional faults,widely developed in the Pearl River Mouth Basin as links between the deep source rocks and shallow reservoirs,are the key to the analysis of hydrocarbon migration and accumulation.Using 3D seismic and drilling data,the growth process and fault transmissibility for the E18 transtensional fault system in the Enping Sag of the Pearl River Mouth Basin are studied in this paper.With Throw-x profiles,Throw-depth profiles,and fault slip-rate diagrams,the growth process of the E18 fault system in each period is restored for sectional activities of the echelon fault system.Evaluation of hydrocarbon lateral migration across the echelon fault system is also studied according to the characteristics of lithological juxtaposition,shale smearing,internal structure(fault cores),and column height.The results show that the E18 fault system was a single fault in rifting period,with a activity center in the western section.However,during post-rifting dextral strike-slip stage,it became dextral left-step in echelon,having an activity center in the central part.Then,two great vertical migration centers of the E18 fault system are determined,with the maximum activity rate up to 20 m/Ma,corresponding a massive hydrocarbon expulsion period(10 Ma-Now).Finally,it is concluded that the linking sections of the E18 fault system in the Zhuhai Formation and lower Hanjiang Formation are the favorable locations for hydrocarbon lateral migration across the fault surface.Accurate analysis of the E18 fault system would help to understand the formation of E18a and E18f oil fields.