摘要
中国南方茅口组地层为区域性烃源岩.茅口组底部和顶部均发育硅质岩,顶部地层残余有机碳高达10.90%,其厚度16m,为优质烃源岩层,而该组底部为差烃源岩.通过岩石学、碳同位素和微量元素分析,表明华南川西北地区茅口期存在2期上升流,分别发育于茅口组沉积早期和晚期;上升流所带来的营养盐有利于生物的发育,产生高的初级生产力.结合碳同位素资料,发现茅口期古海洋生物产率呈现出高-低-高的变化过程,而大气中CO2含量变化也呈现高-低-高的变化过程.虽然茅口期底部为高初级生产力层段,但是由于该沉积及早期成岩阶段为常氧环境,不利于沉积有机质保存,形成了差烃源岩,而茅口组顶部沉积时期存在大的海侵事件,海平面的上升导致厌氧环境形成,沉积有机质大量保存下来,形成优质烃源岩层段.该套烃源岩形成与发育主控因素分析是中国南方海相优质烃源岩分布预测和油气成藏研究的基础.
The Permian Maokou Formation in southern China is taken as regional source rocks.Both the bottom and the top layers of Maokou Formation at the Shangsi section in Guangyuan,Northwest Sichuan developed siliceous rocks,however,only the top layer is taken as excellent source rocks with a thickness of 16 m and the maxium residual organic carbon of 10.90%.Based on the analysis of petrology,carbon isotopes and trace elements,it suggests the existence of upwelling in both the Wordian and Capitanian periods.Nutrient elements brought by upwelling are beneficial to form high primary productivity.The paleo-oceanic phytoplankton growth rate became from high to low and finally to high which coincided with the changes of atmospheric pCO2.The lower Maokou Formation with high primary productivity is poor source rock.The reason is that normoxic environment during the deposition and earlier diagenesis stages of the lower Maokou Formation went against the conservation of organic matter.While the upper Maokou Formation with high primary productivity is taken as excellent source rocks,as a great transgression event during Late Maokou period result in the occurrence of anaerobic environment which led to the formation of excellent source rock layer.The study on the controlling factors in the formation of excellent source rocks in the Maokou Formation is the base of distribution prediction of marine excellent source rocks and hydrocarbon reservoirs prediction in southern China.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
2012年第1期171-180,共10页
Earth Science-Journal of China University of Geosciences
基金
中国石油化工股份有限公司海相油气勘探前瞻性项目(No.G0800-06-ZS-319)
湖北省自然科学重点基金(No.2008CDA095)
地质过程与矿产资源国家重点实验室开放课题(No.GPMR200914)
中国地质大学(武汉)构造与油气资源教育部重点实验室开放基金项目(No.TPR-2010-07)
关键词
海相优质烃源岩
岩石学
碳同位素
上升流
茅口组
二叠系
川西北
地层学
excellent marine source rock
petrology
carbon isotope
upwelling
Maokou Formation
Permian
Northwest Sichuan
stratigraphy
