松南西斜坡三角洲前缘—滑塌浊积岩沉积相及展布规律

Sedimentary Facies and Distribution of Delta Front-Fluxoturbidite in the Western Slope of South Songliao Basin

为厘清坳陷湖盆缓坡背景下形成的浊积体的沉积特征及分布规律,选取松南西斜坡缓坡带晚白垩世青一二段发育的滑塌浊积体作为研究对象,根据岩心和钻测井资料,并结合地震解释,对其沉积相及展布规律进行了研究.该区主要发育三角洲前缘-滑塌浊积岩体系,作为油气储层的滑塌浊积岩可以识别出浊积水道、浊积舌状体、浊积席状砂3种微相类型;在沉积相对比与平面展布特征分析的基础上建立了坳陷湖盆缓坡带浊积体沉积发育模式,认为研究区发育的浊积岩主要为线物源、砂泥质浊积岩沉积模式;与断陷盆地发育的三角洲前缘滑塌浊积岩相比,由于大型坳陷盆地缓坡带断裂作用弱,构造坡折带坡度小,三角洲前缘沉积物再搬运作用相对较弱,浊积岩规模相对较小、粒度较细.此外,与断陷盆地不同,坳陷湖盆内滑塌浊积岩主要发育于三级旋回(层序)基准面上升期,在四级旋回内浊积岩的富集也与湖侵作用密切相关.

In order to understand the sedimentary characteristics and distribution of the turbidites developed at the gentle slope of depression basins,the upper Cretaceous Qing12 members at the western slope of South Songliao basin is chosen as the research object.Its sedimentary facies and distribution are studied by investigating the cores,logging data and seismic interpretation.This area mainly developed delta front-fluxoturbidite system,and the fluxoturbidites in the study area which are the oil and gas reservoir can be divided into the following three micro-facies： turbidite channel,turbidite lobe and turbidite sheet sand.Based on the sedimentary facies correlation and distribution analysis,the depositional model of the fluxoturbidites developed on the gentle slope of depression basins was built,which is the linear-source mud/sand turbidites model.Compared with rift basins,the scale of fluxoturbidites developed in depression basins is relatively smaller and the grain size of it is finer because the fault activity of gentle slope in depression basin is very weak and its slope with lower angle.Furthermore,different from the rift basin,fluxoturbidites in depression basin mainly developed in the base level rise phase of 3rd sequence and its accumulation is also closely related to the transgression in the 4th sequence.