压性浅水湖盆沉积体系——以吐鲁番坳陷中下侏罗统为例

Study on the sedimentary systems of compressed shallow-lake basin:taking middle—lower Jurassic in Turpan Depression as an example

为了探讨压性浅水湖盆沉积体系的分布规律,运用沉积学理论,通过野外露头考察、钻井岩心观察、岩心薄片鉴定以及大量测井、地震等资料的详细分析,认为吐鲁番坳陷中下侏罗统发育了辫状河、辫状河三角洲、曲流河、曲流河三角洲、扇三角洲和湖泊等6种沉积体系,并发现曲流河-曲流河三角洲体系在中下侏罗统中占有相当的比重.依据层序地层学研究结果,将吐鲁番坳陷中下侏罗统细分为5个三级层序,10个四级旋回.对各旋回发育期的沉积体系展布特征进行了深入研究,总结出压性浅水湖盆有缓坡型和具沉积坡折型2种沉积发育模式,在此基础上预测出3个有利储层发育区,即台北凹陷中部、台北凹陷南部和盆地南部边缘带.

The distribution law of the sedimentary systems in the compressed shallow-lake basin are discussed based on sedimentology and detailed outcrop,core,core thin-section identification,logging and seism data,and it is held that six sedimentary systems are developed in middle—lower Jurassic in Turpan Depression,including braided river,braided-river delta,meandering river,meandering-river delta,fan delta and lake systems.It is also found that meandering river and meandering delta systems account for greater proportion in Middle-lower Jurassic.The Middle-lower Jurassic is divided into five third-order sequences and ten fourth-order cycles according to the research results of sequence stratigraphy.The distribution features of the sedimentary systems in each cycle are analyzed,and it is held that there are two sediment developing patterns of gentle-slope type and deposit slope-break type in the compressed shallow-lake basin.Moreover,three favorable reservoir areas are forecasted and they are the central part of Taibei Sag,the southern part of Taibei Sag and the southern marginal part of the basin.