【摘要】 徐家围子断陷下白垩统营城组四段是裂谷盆地火山喷发背景下发育的粗碎屑岩地层,是天然气储层。利用该区钻井、岩芯、测井和高分辨率三维地震资料,按照层序地层的原理对营四段层序地层进行了分析,以岩相分析为基础确定了营四段沉积体系类型。研究表明徐家围子断陷营四段发育营四下层序(Sq1)和营四上层序(Sq2)两个三级层序。营四下层序发育在火山喷发后形成的孤立的3个火山湖盆之中;营四上层序(Sq2)发育在湖盆整体下沉形成的一个相对完整的湖盆之中。营四下层序发育时期湖盆分割性强、湖泊深浅悬殊,主要发育近物源的冲积扇、扇三角洲沉积体系。以发育粗砾岩,中砾岩相组合为特征。营四上层序发育在一个相对完整的大湖盆之中,发育了规模较大的北部物源辫状河三角洲体系和南部物源河流三角洲沉积体系。以发育中砾岩、细砾岩和粗砂岩相组合为特征。辫状河三角洲沉积体系以发育厚度较大,分布面积较广的砾质辫状平原为特征。河流三角洲以发育近源砾质曲流河为特征。由于湖盆古地貌背景由营四下层序沉积时期的分割性强小湖盆演化为营四上层序沉积时期的相对完整的大湖盆,主要沉积体系也由营四下层序的冲积扇和扇三角州,演变为营四上层序的辫状河三角洲和河流三角洲体系。三角洲前缘相储层物性好是天然气的优质储层。更多还原

【Abstract】 The 4th member of Yingcheng Formation of lower Cretaceous is a series of stratigraphy of coarse clastic rock deposited in a background of volcano erupting of rift basin of Xujiaweizi faulted depression.It is the reservoir for natural gas pool.Using 3D seismic data of high resolution,cores,drilling logs and log curves,the framework of sequence stratigraphy and depositional systems of the 4th member were established by this paper based on sequence principle and the way of lithofacies analysis,respectively.Two third-order sequences were identified in the fourth member of Yingcheng Formation of lower Cretaceous in Xujiaweizi rifted depression.The sequence 1of lower fourth member(Sq1) of Yingcheng Formation was deposited in three geographically isolated volcano lakes formed by volcano erupting;the sequence 2 of the upper fourth member(Sq2) of Yingcheng Formation was deposited in a relative whole lake,because of the depression subsidence.Lakes during Sq1 period were well divided,in great disparity of depth,and mostly developed sedimentary systems of alluvial fan and fan delta being adjacent to the uplifts and characterized by lithofacies associations of cobble conglomerate and pebble conglomerate.Sq2 was formed in a relative whole lake,and developed a large scale sedimentary system of braided delta in the northern part of the depression and a sedimentary system of fluvial delta in the southern part of the depression.The two kinds of sedimentary system are characterized by lithofacies assemblages of pebble conglomerate,granular conglomerate,and coarse sandstone.The depositional system of braided delta is characterized by braided delta plain,composed of conglomerates,the thickness of which is great and the area of which is large.The depositional system of fluvial delta is characterized by proximal meandering river of conglomerate.Because of evolution of paleogeomorphology background from three small isolated lakes during Sq1 period to a relative whole lake in Sq2,depositional systems of alluvial fan and fan delta during Sq1 period changed to depositional system of braided river delta and depositional system of fluvial delta during Sq2 period.The front of delta is good reservoirs favorable for nature gas.更多还原