大型坳陷湖盆沉积坡折带特征及其对砂体与油气的控制作用——以鄂尔多斯盆地三叠系延长组为例  

Characteristics of Slope Break Belt in Large Depression Lacustrine Basin and Its Controlling Effect on Sandbody and Petroleum:Taking the Triassic Yanchang Formation in the Ordos Basin as an example

作　　者：李相博[1] 刘化清[1] 陈启林[1] 完颜容[1] 魏立花[1] 冯明[1] 廖建波[1] 马玉虎[1] 

机构地区：[1]中国石油勘探开发研究院西北分院,兰州730020

出　　处：《沉积学报》2010年第4期717-729,共13页Acta Sedimentologica Sinica

基　　金：中国石油天然气股份有限公司项目(合同编号:070103-1)资助研究成果

摘　　要：在海相盆地和断陷湖盆中都发育坡折带,并对层序和沉积起重要控制作用,这一观点已得到广泛关注并被普遍接受。利用地震反射剖面及沉积微相组合特征,对鄂尔多斯盆地三叠系延长组的研究表明,在大型坳陷湖盆中也发育坡折带,按照在湖盆中的所处位置,可明显划分出深水沉积坡折与浅水沉积坡折两类,前者位于三角洲坡型前缘深水区,后者位于三角洲台型前缘或三角洲平原附近。研究表明,深水沉积坡折主要控制砂质碎屑流与浊流等深水重力流砂体沉积,浅水沉积坡折主要控制正常牵引流三角洲前缘水下分流河道砂体沉积。进一步研究认为,除对砂体成因类型具有控制作用外,深水与浅水沉积坡折对延长组中部砂体厚度变化、平面展布形态以及砂体物性变化也具有明显控制作用。在此基础上,文章还讨论了坡折带对油气分布的控制作用,认为延长组油气分布受坡折带与层序格架双重控制,坡上/坡下、高位域/低位域/水进域均能成藏,但规模较大的油气田大多数都位于层序界面附近,要么受坡折带控制,要么受低位域砂体控制,或者二者共同控制。The viewpoint that slope break belt developed both in the marine basin and the nomarine rift basin played important controlling effect on sequence and sediment frameworks has got extensive concern and been widely accepted in recent years.According to the combination characteristic of seismic profiles and sedimentary microfacies,studies on the Triassic Yanchang Formation in the Ordos basin show that sedimentary slope break belts were also developed in the large depression lacustrine basin,and could be clearly recognized either in the deep water or in the shallow water.Deposits of the deep-water gravity flows such as the sandy debris flows and the turbidity flows were mainly controlled by the slope break belt in deep water,whereas deposits of tractive current like subaqueous distributary channels in the delta-front were controlled by that in the shallow water.Further studies suggest that,except for sandbody origin types,the deep-water and shallow-water sedimentary slope breaks also have obvious controlling effect on thickness,plane distribution,and physical properties of the sandstones. In addition,it is suggested that petroleum distribution was also controlled to a certain extent by the slope break belt.Although oil reservoirs can be found everywhere in the Yanchang Formation,most of the larger lithologic reservoirs are located either below the slope breaks or in the LST（lowstand systems tracts） sandstones neighboring the sequence boundary,or controlled by both of the slop break belt and the sequence boundary.

关 键 词：坡折带 砂质碎屑流 沉积物重力流 坳陷湖盆 延长组 鄂尔多斯盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]