渤海湾盆地束鹿凹陷中南部沙三下亚段致密泥灰岩储层分布预测

摘要

This paper focuses on the tight marlstone reservoir in lower 3 rd Member of the Shahejie Formation in central and southern Shulu sag , Bohai Bay Basin .The reservoir is of great economic potential , and has the same characteristics as tight oil reservoir ,such as reservoir-source coexisting ,continuous distribution ,oil-bearing but unclear boundary .Owing to its tight physical property and complex sedimentary environment ,it is challenging to precisely predict distribution of the marlstone reservoir .In this paper , we presented a comprehensive geophysical workflow for prediction of tight marlstone reservoir.Firstly,the geological and geophysical features of the reservoir are studied .Secondly,multiple wells correlation and well-to-seismic calibration are carried out .Thereafter seismic-based sequential stratigraphy frameworks are estab-lished ,and depositional units are identified .Then qualitative interpretation for the target reservoir is carried out by using techniques including geophysical modeling ,basic seismic attributes analysis and post-stack impedance inversion .Finally, spatial and temporal reservoir distribution is analyzed with the integration of strata slicing technique , seismic attributes analysis and sequential boundary constraints .The results show that the lower 3rd Member of Shahejie Formation can be considered as a complete third-order sequence , and the distribution range of the target reservoir becomes wider as the depositional stages changes from low system tract ,to transgressive system tract and finally to high system tract .The reser-voir is thickest in central sag ,while it is relatively pure and the most extensive in late stage of transgressive system tract . The inner slope has well-developed faults with NEE strike ,and interbedded conglomerate and marlstone , thus is a favora-ble area for further exploration .%渤海湾盆地束鹿凹陷中南部古近系沙河街组三段下亚段（沙三下亚段）泥灰岩储层非常致密，具有源储一体、大面积连续分布、含油性好且边界不受构造控制等特性，勘探潜力巨大。但由于沙三下亚段岩性复杂、泥灰岩储层物性很差且非均质性强，储层预测难度大。为此在储层基本特征分析的基础上，提出针对致密泥灰岩储层的地球物理综合预测技术。首先，通过多井对比及井-震精细标定建立地震层序框架，细分沉积单元，落实构造背景；然后，采用地质模型正演、基本地震属性分析、叠后波阻抗反演等处理分析技术开展致密储层定性解释；最后，在地震层序界面约束下结合地层切片技术对致密泥灰岩储层开展三维时空动态分布预测。综合研究结果表明，研究区沙三下亚段为一个完整的三级层序；泥灰岩储层空间分布范围随沉积阶段由低位域-湖侵域-高位域变化而逐步扩大。其中，洼槽区为沉积中心，其泥灰岩厚度最大；湖侵域晚期泥灰岩分布范围最广，且相对较纯；而临近洼槽区的西斜坡内带北北东向断裂发育，泥灰岩与砾岩交互沉积，为寻找勘探甜点的有利区域。