鄂尔多斯盆地西南部与中东部奥陶系马家沟组碳酸盐岩地球化学特征对比  

Comparisons of Geochemical Characteristics of Ordovician Majiagou Carbonate Rocks between West and South and Central and East Regions of Ordos Basin

作　　者：王万春[1] 郑建京[1] 王晓锋[1] 王作栋[1] 罗厚勇[1] 

机构地区：[1]甘肃省油气资源研究重点实验室/中国科学院油气资源研究重点实验室,甘肃兰州730000

出　　处：《天然气地球科学》2015年第3期513-523,共11页Natural Gas Geoscience

基　　金：国家重点基础研究发展规划项目(编号:2012CB214801);国家科技重大专项(编号:2011ZX05005-001);甘肃省重点实验室专项(编号:1309RTSA041)联合资助

摘　　要：鄂尔多斯盆地奥陶系马家沟组碳酸盐岩是否能够作为有效烃源岩以及有效烃源岩的主要分布区域,这对中部气田天然气来源的认识至关重要。通过对比研究鄂尔多斯盆地西部、南部和中东部地区奥陶系马家沟组碳酸盐岩有机碳含量、氯仿沥青"A"含量以及饱和烃生物标志化合物特征,分析其与鄂尔多斯盆地马家沟组沉积环境的关系,认为鄂尔多斯盆地西部和南部以开阔海相沉积为主的马家沟组碳酸盐岩沉积于弱氧化—弱还原环境,有机碳含量普遍低,TOC值高于0.3%的有效气源岩所占比例低;中东部以咸化潟湖或台地蒸发沉积为主的奥陶系马家沟组碳酸盐岩沉积于强还原环境,有机碳含量高于西部和南部马家沟组碳酸盐岩,TOC值高于0.3%的有效气源岩所占比例较高,很有可能是中部气田奥陶系来源天然气,即油型气的主要烃源岩。The central gas field in the Ordos Basin is one of the largest gas fields in China. The source and origin of natural gas from the Ordovician paleo-weathering crust have been studied extensively but remained unclear since the discovery of the gas field. It is of significantly importance for the source of the natural gas of the central gas field to understand whether the carbonate rocks of the Majiagou Formation of the Ordovician in the Ordos Basin are effective source rocks or not and where is the main distributing area of the effective source rocks. Comparative study of organic carbon contents, chloroform asphalt ＂A＂ contents and characteristics of biomarker compounds of saturated hydrocarbons of the carbonate rocks of the Majiagou Formation of the Ordovician in the west and south and central and east regions,and the analysis of the relationship between the geochemical characteristics and depositional environments of the Majiagou Formation of the Ordos Basin,reveal that the carbonate rocks of the Majiagou Formation in the west and south regions of the Ordos Basin, deposited mainly under open marine, weakly oxidized to weakly deoxidized environment ,generally show low organic carbon content and low proportion of effective gas source rock with TOC higher than 0.3% ;while the carbonate rocks of the Majiagou Formation in the central and east regions of the Ordos Basin, deposited under lagoon or platform evaporate, strong deoxidized environment, show relatively higher organic carbon content and high proportion of the effective gas source rock with TOC higher than 0.3%. It could be proposed that the carbonate rock of the Majiagou Formation in the central and east regions of the Ordos Basin is the main source rock of oil-type natural gas accumulated in the central gas field.

关 键 词：鄂尔多斯盆地 马家沟组 有机碳 饱和烃 生物标志化合物 

分 类 号：TE122.113[石油与天然气工程—油气勘探]