福山凹陷西部地区原油地化特征与油源对比

Geochemical Characteristics of Crude Oil and Oil-Source Correlation in the Western Fushan Depression

福山凹陷是北部湾盆地的重要含油气单元,是一个"小而肥"的富生烃凹陷.充分利用烃源岩和原油的有机地球化学等分析测试数据,针对凹陷内研究较少的西部地区的原油进行地化特征分析,进而研究该区油气藏的油源.研究结果显示凹陷西部原油主要为轻质油,族组分以高饱和烃和芳烃含量、低非烃+沥青质含量为特点.凹陷西部的原油生油母质为陆源高等植物和低等水生生物的混合来源,为陆相湖盆混合型母质特征,不同区块不同层段原油的生油母质具有一定的差别.研究区生油母质沉积环境为偏淡水氧化沉积环境的湖沼相,结合原油成熟度,可将研究区原油划分为3类:(1)美台-红光流三上段原油,具有"中等成熟度,低奥利烷含量"特征;(2)永安流一上段原油,具有"高成熟度,高奥利烷含量"特征;(3)朝阳流一上段原油,具有"低成熟度,中等奥利烷含量"特征.进一步油源对比结果显示,美台-红光地区流三段原油来自流三段和流二下段烃源岩,而永安地区的流一段烃源岩为永安地区的原油提供油源.

Fushan depression is a small and resource-rich petroltferous depression,and becomes one of the significant petroleum units in Beibuwan Basin.Making full use of organic geochemical data from source rock and oil,the paper focuses on the geo-chemical characteristics of crude oil in the western Fushan depression which few documents mentioned,and probes into the source of typical reservoirs.It is shown that the petroleum is mainly light oil with high content of saturated hydrocarbon and ar-omatic and low content of asphaltene and non-hydrocarbon matter.The kerogen is made up of terrestrial higher plants mixed with lower aquatic organisms,and is typical of the hybrid sources just as that of continental basin.The feature of kerogen from different area and layers are diversity.The sedimentary environment is partial oxidation and freshwater lacustrine.Combined with maturity of petroleum,the crude oil can be classified as three categories.The first class of oil is characteristic of medium maturity and low content of Ol occurred in the upper part of Third Member of Liushagang Formation （Els3 ）.The second class is found in upper part of First Member in Liushanggang Formation （Els1 ）in Yong＆#39;an area,with high maturity and high con-tent of Oleane （Ol）.The third class also comes from upper part of Els1 in Chaoyang area,and its maturity is low with the me-dium content of Ol.Further studies on the oil-source correlation indicated that the oil in Els3 originates from the source rock in the Els3 and lower part of Els2 in Meitai and Hongguang area,and the source rock from Els1 in Yong＆#39;an area is the main oil source for the oil in Els1 .