东海陆架盆地南部中生代构造-沉积演化与油气勘探方向

Tectono-sedimentary evolution of the Mesozoic in the southern East China Sea Shelf Basin and its bearing on petroleum exploration

  • 摘要: 东海陆架盆地位于欧亚板块东南缘,中生代以来盆地形成和演化过程受到古太平洋板块多期洋壳俯冲及其多构造体系叠加改造,其盆地原型、构造-沉积演化与油气成藏关系一直是研究的热点。本文综合应用东海陆架盆地南部最新地震调查、钻井和临近陆域资料,通过海陆对比、中生界层序地层建立、构造-沉积演化过程重塑,探讨中生界油气成藏的关键问题和勘探方向。研究结果认为东海陆架盆地南部中生界存在2个超层序7个层序,中生代以来演化表现为晚三叠世前的被动大陆边缘基底、晚三叠世—中侏罗世活动大陆边缘拗陷、白垩纪活动陆缘断陷盆地;早期基底NE向格架控制中生代盆地结构与宏观含油气性,中生代两期构造演化造就了两套生储盖组合,基隆运动、渔山运动和雁荡运动控制早期油气的生成、聚集,龙井运动主要控制早期油气藏调整与改造、再成藏;继承性隆起(斜坡)闽江斜坡和“凹中凸”台北转折带是中生界油气主要勘探方向。

     

    Abstract: The East China Sea Shelf Basin is located on the southeastern margin of the Eurasian Plate. Since Mesozoic, the formation and evolution of the basin are characterized by multiphase oceanic subduction of the Paleo-Pacific plate and superimposition of multistage tectonic systems. As the results, many questions, such as prototype of the basin, tectono-sedimentary evolution and hydrocarbon accumulation, have always remained in puzzle. Based on the latest seismic surveys and the drilling data from adjacent land areas, this paper is devoted to the key problems and exploration directions of the Mesozoic hydrocarbon accumulations, through sea-land correlation, establishment of Mesozoic sequence stratigraphy and remodeling of tectono-sedimentary evolution process. It is found that there are two super-sequences and seven seismic sequences in the Mesozoic in the basin. It was a passive continental margin before Late Triassic, an active continental margin depression in Late Triassic-Middle Jurassic, but a faulted basin on an active continental margin in Cretaceous. It is proposed that the basement of the basin in early stage was in NE direction which controls the framework of the Mesozoic basin and macroscopic hydrocarbon-bearing properties. Corresponding to the two-stages of tectonics, there are two sets of Mesozoic source-reservoir-caprock combinations. The Keelung movement, Yushan movement and Yandang movement dominated the formation and accumulation of early-stage oil and gas, while the Longjing movement contributed to the reform of oil and gas reservoirs. Inherited uplifts (slope), such as the Minjiang slope and the " uplifts in depressions” in the Taipei transitional zone, are the main petroleum exploration targets in the future to come.

     

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