鄂尔多斯盆地晚三叠世构造活动及对优质烃源岩发育的影响  

Tectonic Activity of Late Triassic in Ordos Basin and Its Effect on the Formation of High Quality Source Rocks

作　　者：熊林芳[1] 刘池阳[1] 邱欣卫[1] 杜芳鹏 

机构地区：[1]西北大学大陆动力学国家重点实验室,西安710069

出　　处：《地质科技情报》2015年第2期109-114,136,共7页Geological Science and Technology Information

基　　金：国家科技油气重大专项(2011ZX05001-004)

摘　　要：鄂尔多斯盆地三叠系延长组长7段发育一套优质烃源岩,然而关于这套优质烃源岩发育的控制因素的研究相对有限,通过对这套优质烃源岩岩心观察与薄片分析,结合有关延长组岩石学、湖盆底形、沉积环境等方面的研究,确定鄂尔多斯盆地晚三叠世存在构造活动并探讨了这次构造对长7段优质烃源岩发育的影响。结果表明,鄂尔多斯盆地晚三叠世长8末-长7初存在一次构造活动,此次构造活动引起湖盆快速扩张,在湖盆内产生了多种响应,如盆地西南部湖盆底形变陡,沉积体系由曲流河体系变为辫状河-三角洲-湖泊体系,沉积物源发生改变,沉积中心向西南方向迁移,事件沉积丰富等。此次构造活动对长7段优质烃源岩的形成具有重要影响,主要体现在:1构造活动使得湖盆扩张,浮游生物生存空间增加,火山物质为生物繁盛提供了养分,极大地提高了生物生产力;2构造活动导致湖盆水体加深并分层,底层水体形成还原环境有利于有机质保存;3火山物质形成的凝灰岩与优质烃源岩互层沉积,可能为烃源岩提供大量U元素作为催化剂,促进烃源岩生烃演化。There are high quality source rocks of late Triassic in Ordos Basin.However,our understanding about controlling factors of these high quality source rocks is relatively limited.Based on previous researches about petrological characteristics,sedimentary environment,basin bottom morphology and event deposits of Chang-7Formation,according to core observation and thin section analysis,this paper discusses tectonic activity in Late Triassic in Ordos Baisn and its effects on the formation of high quality source rocks.The results show that there was a tectonic activity in Late Triassic in Ordos Basin between the deposition process of Chang-8and Chang-7formations.Abundant evidence of the tectonic activity could be found,for example,basin bottom morphology changed from gentle slope to steep slope,basin structure changed from symmetrical to asymmetrical,depocenter migrated toward northwest,sedimentary facies changed from meandering delta to braided delta,seismite and tuff were formed,and so on.This tectonic activity had remarkable influence on the formation of high quality source rocks in Chang-7Formation.Firstly,tuff provided nutrient for the blooming of planktons and raised the primary productive of the palaeo-lake,which was benefit for the development of high quality source rocks.Secondly,lake basin deepened and resulted in the bottom water forming reducing environment so that sedimentary organic matter can be preserved well.Finally,there was a lot of U in the tuff,which moved into source rocks and helped them generate and expulse hydrocarbon quickly and effectively.

关 键 词：鄂尔多斯盆地 延长组 构造活动 优质烃源岩 

分 类 号：P534.51[天文地球—古生物学与地层学] P618.13[天文地球—地质学]