松辽盆地古龙页岩纳米孔缝形成机制与页岩油富集特征

Formation mechanisms of nano-scale pores/fissures and shale oil enrichment characteristics for Gulong shale， Songliao Basin

孙龙德 王小军 冯子辉 邵红梅 曾花森 高波 江航

Longde SUN Xiaojun WANG Zihui FENG Hongmei SHAO Huasen ZENG Bo GAO Hang JIANG

松辽盆地白垩系古龙页岩油储集层为富有机质、高黏土的陆相页岩，夹少量薄层的钙质砂岩和白云岩，其孔缝体系和页岩油富集规律研究还比较薄弱。基于松辽盆地古龙页岩氩离子抛光-场发射扫描电镜、能谱分析、高压压汞、低温氮气吸附、荧光薄片鉴定、X射线衍射全岩矿物分析、地球化学等实验分析数据，研究了古龙页岩有机-无机孔缝体系及其与页岩油富集的关系。结果表明：①古龙页岩发育基质孔和微裂缝构成的双孔介质储集体系，基质孔为页岩油提供富集空间，微裂缝为页岩油提供储集空间和渗流通道；②受矿物演化、有机质生烃和原油裂解转化等多因素控制，古龙页岩在不同演化阶段发育不同的孔缝组合，其中在成熟演化阶段主要发育微米级溶蚀孔和有机黏土复合孔缝，高成熟演化阶段主要发育纳米级有机黏土复合孔缝和页理缝；③古龙页岩油的富集与孔缝组合演化具有耦合关系，低成熟演化阶段页岩油主要富集于无机粒间孔和晶间孔中，成熟演化阶段页岩油主要富集于溶蚀孔和有机黏土复合孔缝内，油质较重，高成熟演化阶段页岩油主要富集于有机黏土复合孔缝和页理缝中，油质变轻。

The Cretaceous Gulong shale oil reservoirs in the Songliao Basin are composed of organic-rich continental shales with high clay content， interbedded with minor amounts of thinly laminated calcareous sandstones and dolomites. Currently， there is a lack of studies on the pore-fissure system and shale oil enrichment pattern of these reservoirs. Based on the data from experiments and analyses including argon ion milling-field emission scanning electron microscopy （FE-SEM）， energy-dispersive X-ray spectroscopy （EDS）， high-pressure mercury injection analysis， low-temperature nitrogen adsorption experiment， fluorescence thin section observation， X-ray diffraction （XRD） mineralogy of whole rock， and geochemical analysis， we investigate the organic-inorganic pore-fissure system in the Gulong shale and its relationship with shale oil enrichment. The results are as follows： （1） The Gulong shale hosts a dual-porosity reservoir system consisting of matrix pores and microfissures. Matrix pores serve as shale oil enrichment spaces， while microfissures provide both storage spaces and seepage pathways for shale oil； （2） Influenced by multiple factors such as mineral evolution， hydrocarbon generation， and cracking and conversion of crude oil， the Gulong shale exhibits varying pore-fissure combinations at different evolutionary stages. At the mature stage， the shale predominantly contains micron-scale dissolved pores and organo-clay complex pores/fissures （i.e.， pores/fissures with clay minerals as framework and formed as a result of hydrocarbon generation）. In contrast， the highly mature stage is characterized by nano-scale organo-clay-complex pores/fissures and bedding fissures； （3） There exists a coupling relationship between the shale oil enrichment and the evolution of pore-fissure combinations for the Gulong shale. The shale oil primarily accumulates within inorganic intergranular and intercrystalline pores at the low mature stage， while it is relatively heavy and predominantly concentrates in dissolved pores and organo-clay complex pores/fissures at the mature stage. At the highly mature stage， the shale oil becomes lighter and largely gets enriched in organo-clay complex pores/fissures and bedding fissures.

10.11743/ogg20230602