致密砂岩储层成岩史与成藏史耦合关系研究——以南堡凹陷滩海地区沙一段为例

Coupling relationship between diagenetic evolution and hydrocarbon accumulation of tight sandstone reservoir: A case study of the first member of Shahejie formation in the beach area of Nanpu sag

为厘清渤海湾盆地南堡凹陷滩海地区沙一段致密砂岩储层成岩史与成藏史耦合关系,采用薄片、扫描电镜、流体包裹体等测试手段,在致密砂岩储层成岩作用特征分析的基础上,研究了致密砂岩储层的孔隙演化史和油气充注史,认为成岩史与成藏史之间的耦合关系控制了致密砂岩储层的油气成藏.研究结果表明:储层主要经历了压实、胶结、溶蚀等成岩作用,其中压实作用是造成储层物性变差的最主要因素,而胶结作用则是导致储层致密化的根本因素,储层致密化时间约在距今9.7 Ma;储层经历了馆陶组晚期-明化镇组早期(距今15 Ma至12Ma)和明化镇组中晚期(距今7 Ma至2Ma)两期油气充注.因此,南堡凹陷滩海地区沙一段致密砂岩储层成岩史与成藏史之间存在"先成藏后致密型"和"先致密后成藏型"2种耦合关系,分别对应2种致密油成藏模式,后者可作为今后勘探的重点目标区域.

To clarify the coupling relationship between diagenetic evolution and hydrocarbon accumulation of tight sandstone reservoir of the first member of Shahejie formation in the beach area of Nanpu sag, the history of pore evolution and hydrocarbon charge of tight sandstone reservoir were studied based on diagenesis characteristics by methods of cast thin sections, SEM and fluid inclusions test. It indicates that diagenetic history and accumulation history in tight sandstone reservoir have significant coupling relationship controlling the hydrocarbon accumulation of tight sandstone reservoir. The results show that tight sandstone reservoir has mainly experienced compaction, cementation and dissolution during its formation process. Among them, compaction is the major factor of worse physical property, while cementation is the primary cause of reservoir densification, and the reservoir densification period is about 9.7 Ma. The tight sandstone reservoir is characterized by two periods of charge during late Guantao formation-early Minghuazhen formation(15-12 Ma) and middle-late Minghuazhen formation(7-2 Ma). There are two kinds of coupling relationships between diagenetic evolution and hydrocarbon accumulation of tight sandstone reservoir of the first member of Shahejie formation in the beach area of Nanpu sag. The first phase of hydrocarbon charge is before reservoir densification, which belongs to accumulation prior and densification later. The second phase of hydrocarbon charge is after reservoir densification, which belongs to densification prior and accumulation later. Accordingly, there are two hydrocarbon accumulation models of tight sandstone reservoir, and the latter can be the key target of future exploration.