渤海湾盆地西部凹陷南段成岩相分析与优质储层预测

Diagenetic Facies Analysis and High-Quality Reservoir Prediction in the Southern Xibu Depression of the Bohaiwan Basin

储层实测孔隙度、普通薄片、铸体薄片和扫描电镜的资料表明,渤海湾盆地辽河坳陷西部凹陷南段新生界储层在纵向上发育三个次生孔隙带。从而在一个普遍低孔渗背景下,形成了孔隙度相对较高的优质储层。优质储层的形成和分布主要受沉积微相和成岩作用的影响与控制。他们形成于河口坝、辫状分流河道以及心滩沉积微相,目前处于早成岩阶段B期—中成岩阶段A1亚期,发育溶蚀成岩相。该文通过模拟古地温、镜质组反射率、甾烷异构化率和自生石英含量随时间的变化规律,预测了西部凹陷南段成岩阶段和成岩相的横向展布。通过成岩相图和沉积相图的叠合,预测了沙三中亚段优质储层的分布。预测结果表明,优质储层主要发育于斜坡区的中部。

There exist three secondary porosity zones vertically in the Cenozoic reservoirs of the Southern Xibu Depression of the Bohaiwan Basin as revealed by the measured porosity data,thin sections,blue epoxy resin-impregnated thin sections and scanning electron microscopes. As a result, the hlgh-quality reservoirs are developed. Sedimentary microfacies and diageneses control the formations and occurrences of the high-quality reservoirs, which are dominantly formed in the channel mouth bar, braided channel and channel bar deposits, located in the early diagenetic stage Bmiddle diagenetic stage A1 and dissolution diagenetic facies. The diagenetic stages and diagenetic facies are predicted by modeling the paleotemperature, vitrinite reflectance, sterane isomerization rate and authigenic quartz concentration in space and time. The high-quality reservoirs of the third middle member of Shahejie Formation are delineated by superposing the diagenetic facies map on the microfacies map. They are mainly in the middle part of the slop of the Southern Xibu Depression.