页岩中的后油沥青孔隙体系：基本特征、形成机制与页岩油气地质意义

Identification of the type and origin of pore networks in shales is crucial to the study of shale oil and gas geology. Of such pores, those related with post-oil solid bitumens might play significant roles, but have gained relatively little attention. To investigate this issue, this project aims to conduct a detailed study using multiple methods including scanning electron microscope (SEM), microscopic imaging and artificial laboratory source-rock simulation. The basic features, formation mechanisms and implications for shale oil and gas geology will be addressed. First, the identification methodology of the post-oil solid bitumen and its associated pore networks will be established based on a detailed microscopic study. Second, representative shale samples will be performed by artificial thermal simulation. The microscopic features of the pore networks under different maturities will be investigated. This results in the discussion of formation mechanism and factors influencing the formation and evolution of the pore networks, e.g., organic matter and mineral. Third and finally, the relationship between the pore networks and shale oil and gas abundance will be discussed combined with the shale heterogeneities and its shale oil and gas producing features. These results and understandings can provide new theoretical and experimental data for the study of accumulation mechanisms and rules of shale oil and gas, which could be used in practical exploration. In addition, it can also add new complements to the studies of geochemistry and organic petrology of bitumens. Therefore, the project can have fundamentally theoretical and practical exploration implications.

页岩孔隙体系是页岩油气研究的一个关键基础环节，其中后油沥青孔隙体系可能占有重要地位，但前期关注较少。本项申请，拟选择国内勘探已获成功的典型页岩油气实例，应用先进的扫描电镜、显微成像和人工热模拟等技术，开展精细研究，以揭示这类孔隙体系的基本特征、查明形成机制和讨论地质意义为目标。首先，在详细描述后油沥青孔隙特征的基础上，建立后油沥青及其孔隙体系的识别方法和方案。然后，利用热模拟技术，观察并描述典型页岩在不同热模拟阶段残渣样的后油沥青孔隙体系特征，剖析不同有机质和矿物特征对后油沥青孔隙体系的影响，总结影响因素和形成机制。最后，结合页岩非均质性及其油气产出特征，探讨后油沥青孔隙体系与页岩油气富集的关系。研究结果可望为页岩油气富集机理和规律研究提供新的理论和实验依据，供勘探参考，还可望进一步丰富沥青的地球化学和有机岩石学研究，因而具有重要的基础理论与实践应用意义。

页岩油气是当前受到极大关注而得到迅猛发展的一种重要的非常规油气资源，页岩中的孔隙体系以低孔、超低渗和极强的非均质性为主要特征，使得储存大量油气资源的页岩通常很难大量持续产出具有工业价值的油气。因此，页岩中的孔隙体系研究对页岩油气至关重要，其中的后油沥青孔隙体系可能占有重要地位，但目前对这类孔隙体系的研究还很初步，因此开展页岩中的沥青、孔隙及对页岩油气富集的意义开展研究。.项目主要开展了：a）泌阳凹陷页岩的基本地质地球化学特征及沥青成因的识别及其孔隙特征，做出孔隙体系与页岩油气富集关系的结论；b）三塘湖芦草沟组低成熟页岩的热模拟，分析沥青形成的时间及其与孔隙演化的关系；c) 巴奈特页岩地化参数与初次运移的关系；d）开展适用于页岩气流动模拟的孔隙网络模型模型研究，并应用于四川龙马溪组页岩的数字岩心数据。.重要结果：a）泌阳页岩非均质性极强，页岩油有利勘探层位为类型I和类型III叠置或相邻的层段；b）低熟-成熟阶段页岩内的滞留油/残留沥青等会对孔隙有堵塞作用；封闭体系发育有更多的固体沥青、焦沥青孔隙；而半封闭体系有机质中的干酪根孔更为发育，且溶蚀孔含量可能相对少些；c）巴奈特页岩沥青中的含氮吡咯化合物可能来自于叶绿素降解产物，且甾萜类生物标志化合物指标基本不受页岩油初次运移分馏的影响；d）将非达西效应耦合到新孔隙网络模型比传统模型更加准确，适合模拟页岩气流动。.关键数据及其科学意义：积累了不同地区的大量页岩有机和无机地球化学数据及有机岩石学资料及两种不同体系的页岩热模拟产物地化及相关孔、渗及有机岩石学数据。这为不同成熟阶段页岩油气的勘探提供了理论指导，同时新的孔隙网络模型为页岩气流动研究提供了一种新的思路，为准确预测页岩气渗流能力提供理论依据。