川西北茅口组沉积相特征及白云岩成因研究

发布时间：2018-06-12 00:08

本文选题：成都理工大学 + 学位论文　；参考：《成都理工大学》2015年硕士论文

【摘要】：近期我国海相碳酸盐岩油气勘探的实践表明,生物礁、颗粒滩、白云岩、岩溶风化壳等是石油天然气十分重要的碳酸盐储层类型。除岩溶风化壳以外,其余几种商业储层的形成均与白云岩化作用密切相关。因此,对白云岩成因研究也就成为碳酸盐岩储层研究中非常重要的组成部分,而白云岩化作用则成为研究的核心内容。因此,理清白云岩成因问题,对于认识以白云岩及其相关的碳酸盐岩为储层的油气勘探工作尤为重要。本文在前人研究基础上,通过铸体薄片、扫描电镜观察、X-衍射和有序度分析,结合微量元素、碳氧同位素、包裹体测试等分析测试方法,在沉积相分析基础上,系统地研究了川西北茅口组白云岩的岩石学和地球化学特征,主要取得了以下几点认识:1.在结合前人对川西北地区二叠统地层的认识基础上,运用最新的地层资料(岩芯、录井、野外实测等),系统梳理了川西北地区二叠系地层,详细分析了二叠系茅口组的岩性组合规律和特征,并对其进行对比划分,建立了川西北地区二叠统地层划分方案。2.依据沉积学与古生物标志,通过对研究区典型钻井岩心和剖面结构分析,确定川西北茅口组为碳酸盐台地相沉积沉积开阔台地相。参考了塔克提出的碳酸盐沉积相模式,认为川西北中二叠统茅口组属于碳酸盐岩台地沉积体系。3.微量元素分析结构,表明各类粉-细级的晶粒白云岩的Sr含量较高,反映埋藏成岩环境下的白云岩化作用,发生在蒸发浓缩的高盐度海源地层水流体中,而粗-中晶白云岩与加深埋藏过程中由重结晶作用引起的白云石脱Sr作用有关。从δ13C与δ18O关系图中,可看出各类白云岩的δ13C值和δ18O值分布相对集中,其成岩流体性质相似或同源,其中的晶粒白云岩的δ13C值较稳定,而δ18O有较大的负偏,表明白云岩化作用发生在温度较高,成岩流体很可能来源于深循环的、有岩浆热液参与的地层水,说明晶粒白云岩为埋藏白云岩化作用的产物4、流体包裹体特征分析中,据分析表明茅口组方解石主要形成于深埋藏高温环境,进一步证明茅口组白云岩是埋藏期白云岩化作用。
[Abstract]:Recent oil and gas exploration practice of marine carbonate rocks in China shows that reef, granular beach, dolomite and karst weathering crust are very important carbonate reservoir types of petroleum and natural gas. With the exception of karst weathering crust, the formation of other commercial reservoirs is closely related to dolomitization. Therefore, the study of dolomite genesis has become a very important part of carbonate reservoir research, and dolomitization has become the core of the study. Therefore, it is very important to clarify the origin of dolomite in order to understand the oil and gas exploration with dolomite and its related carbonate rock as reservoir. On the basis of the previous studies, the author observed the X-diffraction and order degree of the cast body by scanning electron microscope, combined with trace elements, carbon and oxygen isotopes, inclusions and other analytical methods, on the basis of sedimentary facies analysis. The petrology and geochemistry of dolomite of Maokou formation in northwestern Sichuan are systematically studied. The main results are as follows: 1. Based on the previous understanding of Permian strata in Northwest Sichuan, the Permian strata in Northwest Sichuan are systematically combed with the latest formation data (core, logging, field measurements, etc.) The law and characteristics of lithologic assemblage of Maokou formation of Permian system are analyzed in detail, and the stratigraphic division scheme of Permian Permian in northwestern Sichuan is established. On the basis of sedimentology and paleobiological markers, through the analysis of typical drilling cores and section structure in the study area, it is determined that Maokou formation in northwest Sichuan is a carbonate platform facies sedimentary open platform facies. Referring to the carbonate sedimentary facies model proposed by Tucker, it is considered that the Maokou formation of the Middle Permian in northwestern Sichuan belongs to the carbonate platform sedimentary system. The trace element analysis structure shows that the Sr content of various kinds of silt-fine grain dolomite is relatively high, which reflects the dolomization in buried diagenetic environment and occurs in the high-salinity marine source formation with evaporation and concentration. The coarse-mesocrystalline dolomite is related to the removal of Sr from dolomite by recrystallization in the process of deepening burial. From the diagram of 未 13C and 未 18O, it can be seen that the distribution of 未 13C and 未 18O values of dolomite is relatively concentrated, the diagenetic fluid properties are similar or homologous, the 未 13C value of grain dolomite is relatively stable, and 未 18O has a large negative deviation. The results show that dolomitization occurs at high temperature and diagenetic fluid is probably derived from deep circulation and magmatic hydrothermal fluid, indicating that grain dolomite is the product of buried dolomization, and the fluid inclusion characteristics are analyzed. The analysis shows that the calcite of the Maokou formation was mainly formed in the deep buried high temperature environment, which further proves that the dolomite of the Maokou formation is dolomitization during the burial period.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13

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