鄂尔多斯盆地延长期湖泊热流体活动对烃源岩有机质丰度和类型的影响  

Effects of the lacustrine hydrothermal activity in the Yanchang period on the abundance and type of organic matter in source rocks in the Ordos Basin

作　　者：吉利明 李剑锋 张明震 贺聪 马博 金培红 JI Liming;LI Jianfeng;ZHANG Mingzhen;HE Cong;MA Bo;JIN Peihong(Gansu Key Laboratory of Petroleum Resources,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;National Engineering Laboratory for Exploration and Development of Low-Permeability Oil&Gas Fields,Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi an 710018,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院西北生态环境资源研究院甘肃省油气资源研究重点实验室,甘肃兰州730000 [2]中国科学院广州地球化学研究所有机地球化学国家重点实验室,广东广州510640 [3]中国石油长庆油田分公司勘探开发研究院低渗透油气田勘探开发国家工程实验室,陕西西安710018 [4]中国科学院大学,北京100049

出　　处：《地学前缘》2021年第1期388-401,共14页Earth Science Frontiers

基　　金：国家自然科学基金项目(41672137);有机地球化学国家重点实验室开放基金课题(SKLOG-201701);甘肃省重点实验室专项(1309RTSA041)。

摘　　要：选择鄂尔多斯盆地南部连续取岩心的YK1井延长组样品开展了系统的烃源岩评价、元素地球化学和孢粉相分析,探讨了延长期湖泊热流体活动对烃源岩有机质丰度和类型的影响。以碳质泥岩和油页岩为主的长7-3段发育优质烃源岩,灰黑色泥岩为主的长7-1+2段部分层段发育好的烃源岩,砂泥岩互层的长6段个别层位也可形成较好的烃源岩。热流体活动强度指标Al/(Al+Fe+Mn)和(Fe+Mn)/Ti比值指示,与上述3个烃源岩发育阶段相对应古湖泊经历了3幕明显的热水活动过程,其中长7-3期为热水活动的高峰。YK1井烃源岩可划分出3种孢粉相:孢粉相A分布于长8—长9段和长6-2+3段,主要出现Ⅲ型及少量Ⅱ型有机质,有机碎屑以半透明木质和凝胶化颗粒为主;孢粉相B分布于长7-3段,主要为Ⅰ型和Ⅱ1型有机质,以高丰度藻类体和无定形体有机质为特征;孢粉相C分布于长7-1+2段,主要为Ⅱ型有机质,丰富的无定形体和植物碎屑同时出现。烃源岩总有机碳含量、有机质类型以及主要生烃组分含量均与热水活动强度表现出很好的耦合关系,表明热流体活动可能导致湖泊藻类和浮游生物的繁盛,使烃源岩有机质丰度和质量得到明显提高。热水活动高峰长7-3期发生了藻类勃发和优质烃源岩的沉积。We selected continuous core samples from the Yanchang Formation in Well YK1,southern Ordos Basin to completed a systematic source rock evaluation and geochemical and palynofacies analyses.We discussed the effects of lacustrine lake hydrothermal activity in the Yanchang period on the abundance and type of organic matter in source rocks.Field studies show that the high-quality source rocks developed in the Chang 7-3 interval are mainly carboniferous mudstone and oil shale,the well-developed source rocks from some sections of the Chang 7-1+2 interval are mainly gray-black mudstone,and the individual stratum of the Chang 6 member,interbedded with sandstone and mudstone interlayers,can also form good source rocks.The hydrothermal activity indicators,Al/(Al+Fe+Mn)and(Fe+Mn)/Ti ratios,show that the ancient lake underwent three episodes of significant hydrothermal activity corresponding to the above three stages of source rock development,with the peak intensity in the Chang 7-3 period.The source rock from Well YK1 can be divided into 3 types of palynofacies.Palynofacies A,mainly type III and a small amount of type II organic matter,is distributed in the Chang 89 and Chang 6-2+3 members,where translucent ligno-cellulosic fragments and gelified particles are dominant organic debris.Palynofacies B,distributed in the Chang 7-3 interval,is mainly amorphous typeⅠandⅡ1 organic matter containing high abundance algae.Distributed in the Chang 7-1+2 interval,Palynofacies C is mainly amorphous type II organic matter with simultaneously developed phytoclasts.The source rock total organic carbon content,organic matter type and fraction of hydrocarbon-generating components correlate well with the intensity of hydrothermal activity.It suggests that hydrothermal activity may play a role in the lake algae and plankton proliferation,thereby improving the abundance and quality of organic matter in source rocks.Indeed,our study show that the algae bloom and high-quality source rock deposition occurred during the Chang 7-3 period of peak

关 键 词：鄂尔多斯盆地 三叠系 延长组 优质烃源岩 热流体活动 

分 类 号：P618.13[天文地球—矿床学]