栖霞组中台缘斜坡上升流沉积相及其与烃源岩的关系

UPWELLING DEPOSITS AT THE MARGINAL SLOPE OF A CARBONATE PLATFORM IN QIXIA STAGE AND ITS RELATION WITH HYDROCARBON SOURCE ROCKS

  • 摘要: 栖霞组是我国南方发育的4套区域性海相烃源岩的重要组成部分。通过近年对实测剖面沉积岩石学、有机地球化学和古生物等研究,认为其中梁山段为滨海沼泽、泻湖相,臭灰岩为碳酸盐岩斜坡海进相,上下硅质岩、本部灰岩和顶部灰岩是典型的碳酸盐岩台缘斜坡上升流沉积相,并有风暴沉积参与,可分为4个沉积亚相。分析表明,海相碳酸盐岩烃源岩的TOC下限值要根据不同时代、不同暴露情况来定,不能设一个定值为统一标准。埋藏的栖霞组属较好和优质的烃源岩。栖霞组碳酸盐岩中有机质类型优质,以腐泥型为主,原始生烃潜力较高,烃源岩产能高,处于成熟-高成熟热演化阶段。岩石中泥晶方解石含量与TOC呈正相关,优质烃源岩层位集中在臭灰岩顶部、本部灰岩中上部和顶部灰岩的一些层位。

     

    Abstract: The Qixia Formation is one of the four suites of hydrocarbon source rocks in south China. Through field survey, and organic geochemical and paleontological studies, the authors believe that the Liangshan Member of the Formation is consisted of littoral mash and lagoonal facies; the Stink Limestone belongs to the transgressive carbonate slope facies; and all of the Upper and Lower Silicious Deposits, the Major Limestone and Top Limestone are upwelling slope facies deposited on the edge of a platform, in which storm deposits are observed. The upwelling slope facies could be divided into four sub-facies. Data suggest that it is not appropriate to set up a lower threshold of TOC for marine carbonate hydrocarbon source rocks. The threshold in fact depends upon the age and exposure time of source rocks. The organic matter in the Qixia carbonate is of high quality and dominated by sapropel. The original capacity of hydrocarbon generation is high. The source rocks have passed into a mature or over-mature stage. In the source rocks, the content of micritic carbonate is positively correlated with TOC. High-quality source rocks occur on the top of the Stink Limestone, middle and upper parts of the Major Limestone and some parts of the Top Limestone.

     

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