辽河坳陷西部斜坡带南段新生界成岩相分析与优质储集层预测

Diagenetic facies analysis and high quality reservoir prediction of the Cenozoic in southern segment of western slope of Liaohe Depression

储集层实测孔隙度、普通薄片、铸体薄片和扫描电镜的分析资料表明,渤海湾盆地辽河坳陷西部斜坡带南段新生界储集层在纵向上发育3个次生孔隙带。从而在一个普遍低孔、低渗的背景下,形成了孔隙度相对较高的优质储集层。优质储集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,分别形成于辫状分流河道、河口坝+席状砂沉积微相,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。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,预测了西部斜坡带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,预测了沙河街组三段优质储集层的分布。预测结果表明,沙三段优质储集层发育于斜坡区的中部。

The analyses of measured porosity data, thin sections, casting thin sections and scanning electronic microscopes of the reservoirs indicate that three secondary porosity zones were vertically developed in the Cenozoic reservoirs of the southern segment of the western slope of the Liaohe Depression in the Bohai-wan Basin. As a result, the high quality reservoirs are developed in a generally low porosity and permeability background. Sedimentary microfacies and diagenesis are the main factors controlling the formation and distribution of the high quality reservoirs which were mainly developed as braided channel, mouth-bar and sheet- like sand microfacies. They belong to the early diagenetic stage B to intermediate diagenetic stage A1 and dissolution diagenetic facies were developed. The diagenetic stages and diagenetic facies distribution are predicted by simulating the paleotemperature, vitrinite reflectance, sterane isomerization rate and authigenetic quartz variation in space and time. The distribution of high quality reservoirs of Member 3 of Shahejie Formation is predicted by superimposing the diagenetic facies maps on the microfacies maps. The results show that the high-quality reservoirs of Member 3 of Shahejie Formation were developed in the middle part of the western slope.