乍得南部Bongor盆地下白垩统碎屑岩储层成岩作用及其对物性的影响

综合利用铸体薄片、X射线衍射、阴极发光、扫描电镜、物性分析及镜质体反射率和包裹体温度等资料，结合岩心观察法，对Bongor盆地下白垩统碎屑岩储层基本特征及成岩作用进行了研究。依据胶结物的体积分数及形态、黏土矿物组分的分布、岩石结构镜下特征及孔隙演化、有机质热演化等证据划分了岩石成岩阶段，并分析了成岩作用对物性的影响。结果显示：该区储层岩石类型以长石砂岩为主，胶结物以碳酸盐和黏土矿物为主；溶孔-粒间孔组合型储集性最好，粒间孔-溶孔组合型次之；成岩作用是控制储层物性的主要因素，成岩作用主要包括压实作用、胶结作用、交代作用和溶蚀作用；压实作用和胶结作用是破坏性成岩作用，二者分别使原始孔隙度损失54.93%和31.30%，岩石颗粒中长石、碳酸盐胶结物等易溶物质发育，溶蚀作用是主要建设性成岩作用；目的层成岩阶段以中成岩A期为主，成岩作用弱-中等。

Diagenesis of Lower Cretaceous Clastic Reservoir and Its Influence on Physical Properties in Bongor Basin,Southern Chad

Based on the data of cast thin section, X-ray diffraction, cathodoluminescence, scanning electron microscope, physical property analysis, vitrinite reflectivity and wrapping temperature, combined with core observation method, the basic characteristics and diagenesis of Lower Cretaceous clastic reservoir in Bongor basin are studied. According to the volume fraction and morphology of cement, the distribution of clay mineral components, microscopic characteristics of rock structure, pore evolution and thermal evolution of organic matter, the rock diagenetic stages are divided, and the influence of diagenesis on physical properties is analyzed. The results show that:The reservoir rock type in this area is mainly feldspathic sandstone, and the cement is mainly carbonate and clay minerals; Dissolved pore intergranular pore combination has the best reservoir performance, followed by intergranular pore dissolved pore combination; Diagenesis mainly includes compaction, cementation, metasomatism and dissolution; The diagenetic stage of the target layer is mainly middle diagenetic stage A, and the diagenesis is weak to medium; Diagenesis is the main factor controlling reservoir physical properties. Compaction and cementation are destructive diagenesis, which make the original porosity lose 54.93% and 31.30% respectively; In the rock particles, feldspar, carbonate cement and other soluble substances are developed, with strong dissolution, which is the main constructive diagenesis.