摘要： 陆相页岩油储集层孔隙结构特征及储集能力受泥页岩在埋藏过程中经历的复杂成岩改造影响,纵向上表现出显著的差异性,但相关研究仍不够深入。以渤海湾盆地东营凹陷古近系沙河街组沙四上亚段典型陆相富有机质泥页岩为研究对象,基于岩心观察描述、岩石薄片鉴定、扫描电镜等多尺度观察手段,结合X射线衍射分析、同位素地球化学分析、物性分析及能谱分析等测试资料,开展泥页岩成岩作用特征及其控储差异研究。研究结果表明: (1)研究区可识别出7种成岩作用类型,其中,建设性成岩作用以方解石重结晶、黏土矿物转化及白云石化作用为主; 沙四上亚段整体处于中成岩A阶段。(2)方解石重结晶、黏土矿物转化及白云石化作用在垂向上表现出显著的差异性演化特征,重结晶成因的亮晶方解石主要发育于纯上3小层与纯上2小层,黏土矿物转化所形成的晶间中—高孔区主要发育于纯上2小层; 研究区主要发育2种类型的白云石,其中,泥晶白云石主要发育于纯上3小层,微晶铁白云石主要发育于纯上1、2小层。(3)方解石重结晶和黏土矿物转化的协同使得纯上2小层产生了大量微孔,同时适量的铁白云石可作为骨架矿物支撑孔隙,有利于中深层孔隙的保存,是该小层成为优质储集层的关键。

关键词: 东营凹陷, 沙四上亚段, 成岩演化差异性, 方解石重结晶, 黏土矿物转化

Abstract: The pore structure characteristics and reservoir capacity of continental shale oil reservoirs are affected by the complex diagenetic alteration during burial,resulting in significant vertical differences. However,relevant researches are still limited. This work focuses on the typical continental organic-rich shale of the upper sub-member of Member 4 of Paleogene Shahejie Formation(Es^4U)in Dongying sag,using the multi-scale observation methods like core description,thin section and scanning electron microscopy(SEM)observations,X-ray diffraction,isotope geochemistry,physical property and energy spectrum analysis,to reveal the diagenesis characteristics and its controls on reservoir quality of the shale. Our work has identified that: (1)Seven types of diageneses that can affect reservoir quality. The constructive diagenesis is mainly calcite recrystallization,clay mineral transformation,and dolomitization. The Es^4U is overall in the middle diagenetic stage A. (2)Calcite recrystallization,clay minerals transformation,and dolomitization vary significantly in vertical. The sparry calcite caused by recrystallization is mainly developed in the $Ea^{4Ucs3}$ and the $Ea^{4Ucs2}$ layers. The intermediate and high pores formed by clay minerals transformation are mainly developed in the $Ea^{4Ucs2}$ layer. Based on the petrological characteristics,there are two types of dolomite identified in the study area. Among them,the argillaceous dolomite is mainly developed in the $Ea^{4Ucs3}$ layer,and the microcrystalline iron dolomite is mainly developed in the $Ea^{4Ucs1}$ layer and the $Ea^{4Ucs2}$ layer. (3)The combined actions of calcite recrystallization and clay mineral transformation generate a large number of micropores in the $Ea^{4Ucs2}$ layer. At the same time,moderate iron dolomite is a skeleton mineral to support the pores,conducive to preserving pores in a moderate-deep burial depth. It is the key for the $Ea^{4Ucs2}$ layer to become a high-quality shale-oil reservoir.

Key words: Dongying sag, upper sub-member of Member 4 of Shahejie Formation, diagenetic difference, calcite recrystallization, clay mineral transformation

中图分类号: 

• TE122