乐安油田草4块沙三段—沙二段储层沉积特征与非均质性研究

Reservoir sedimentary characteristics and heterogeneity of second and third members of Shahejie formation in block Cao4, Le'an oilfield

利用地震、钻井、测井、岩心资料,对乐安油田草4块沙三段—沙二段储层的沉积特征与非均质性及隔层和夹层对特稠油油藏开发的影响进行了研究,发现储层沉积特征和非均质性是影响该单元特稠油构造-地层油藏开发生产的重要因素。研究区沙三段—沙二段为辫状河三角洲前缘亚相沉积,水下分流河道和河口坝是储层分布的主体相带。储层层内、层间非均质性强,平面非均质性较弱,砂体连通性较好。隔层和夹层主要为沉积成因,纵向上沙三段隔层和夹层较沙二段不发育,构造高部位因剥蚀造成隔层缺失,水下分流河道部位因冲刷造成隔层不发育。隔层和夹层的平面、垂向分布特征对特稠油油藏注蒸汽热采具有直接影响,沙三段2和3小层的顶底隔层发育,其内部的夹层不发育,应作为主要的提高采收率热采层段。

The reservoir sedimentary characteristics and heterogeneity of the second and third members of Shahejie formation in block Cao4, Le'an oilfield have been studied herein based on seismic, drilling, logging and coring data. The results show that, reservoir sedimentary characteristics and heterogeneity dominate the structural-stratigraphic reservoir production of super -heavy oil significantly. The second and third members of Shahejie formation in studied area belong to braided river delta deposits with chief facies belts of distributary channel and mouth bar. Their inner and inter heterogeneity are very strong with interbeds caused by sedimentation. The third member of Shahejie formation is less developed than the second one in the vertical direction. And, interbeds in the highs lack because of denudation and in the distributary channel for erosion. Both the planar and vertical distribution of interbeds controls the thermal production of super-oil reservoir by steam injection directly. The second and third members of Shahejie formation become the favorable targets for limited interbeds inside and steady barrier beds both on the top and bottom.