松辽盆地三肇凹陷青山口组页岩中碳酸盐矿物成因研究

Genesis of carbonate minerals in shale of Qingshankou Formation, Sanzhao Sag, Songliao Basin

吴霞 陈睿倩 白昕

WU Xia CHEN Ruiqian BAI Xin

中国石油大学(北京) 油气资源与工程全国重点实验室, 北京 102249 中国石油大学(北京) 地球科学学院, 北京 102249

National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China College of Geosciences, China University of Petroleum (Beijing), Beijing 102249, China

为了揭示陆相页岩中碳酸盐矿物对于页岩油气勘探与开发的意义，以松辽盆地三肇凹陷青山口组碳酸盐矿物发育的页岩为研究对象，通过薄片观察、X射线衍射(XRD)、碳氧同位素分析以及主、微量元素分析等实验方法，对碳酸盐矿物的类型及发育特征进行了深入分析，探讨了碳酸盐矿物生成的物质来源和成因机制，并详细说明了碳酸盐矿物发育如何影响页岩油气的富集。研究揭示三肇凹陷青山口组页岩发育三类方解石(生物壳体型碳酸盐、泥晶方解石、亮晶方解石)和两类白云石(泥晶白云石、细晶白云石)。通过稳定碳、氧同位素及主、微量元素的测试分析，表明研究区碳酸盐主要形成于咸化分层、缺氧还原以及中—高生产力的封闭湖泊水体环境中。不同类型的碳酸盐矿物成因各异，生物壳体型碳酸盐、泥晶方解石和泥晶白云石主要受生物化学作用控制，亮晶方解石和细晶白云石则是通过重结晶作用形成。岩石有机碳与岩石热解测定结果表明碳酸盐含量与总有机碳(TOC)含量呈正相关关系，TOC含量与生烃潜量(S1+S2)具有正相关关系，表明陆相页岩中碳酸盐矿物发育的层段是优质页岩的发育层段。同时，与碳酸盐矿物相关的晶间孔和溶蚀孔的形成，为页岩中油气的聚集创造了储存条件。

To reveal the significance of carbonate minerals in continental shale for shale oil and gas exploration and development, this paper takes the carbonate mineral developed shale from the Qingshankou Formation in the Sanzhao Sag of the Songliao Basin as the research object. Through thin-section observation, X-ray diffraction (XRD), carbon and oxygen isotope analysis, and major and trace element analysis, the types and development characteristics of carbonate minerals were analyzed in depth. The material sources and genetic mechanisms for carbonate mineral formation were discussed, and how carbonate mineral development affected shale oil and gas enrichment was explained in detail. The study revealed that the shale from the Qingshankou Formation in the Sanzhao Sag developed three types of calcite (biogenic shell carbonates, micritic calcite, and sparry calcite) and two types of dolomite (micritic and fine-grained dolomite). Through the analysis of stable carbon and oxygen isotopes, and major and trace elements, it was shown that the carbonates in the study area mainly formed in a stratified, anoxic, reducing, and moderately to highly productive environment within a closed saline lake. The genesis of different types of carbonate minerals varied. Biogenic shell carbonates, micritic calcite, and micritic dolomite were mainly controlled by biochemical action, and the sparry calcite and fine-grained dolomite were formed through recrystallization. Results from rock organic carbon content and rock pyrolysis tests indicated a positive correlation between carbonate content and total organic carbon (TOC) content and a positive correlation between TOC content and hydrocarban generation potential(S1+S2)values, indicating that the carbonate mineral developed intervals in continental shale were high-quality shale development zones. Additionally, the formation of intercrystalline and dissolution pores associated with carbonate minerals created storage conditions for the accumulation of oil and gas in the shale.

国家自然科学基金 41702126

https://doi.org/10.11781/sysydz2024061226