黔北凤冈地区龙马溪组页岩储层储集空间划分与演化过程分析

Reservoir space and evolution process of Longmaxi shale in the Fenggang area of northern Guizhou

页岩储集空间的研究是页岩油气研究的核心内容之一,页岩孔隙和裂缝很大程度上影响了页岩储层的储集能力和渗流特征。采用薄片观察、常规扫描电镜观察、氩离子抛光(FIB)、场发射电子显微镜(FESEM)实验,并结合能谱分析(EDS)等技术手段系统分析了研究区龙马溪组页岩储层的储集空间的成因、大小、形态、分布、连通性等特征,以页岩中储集空间的成因及孔隙发育位置特征为依据,分析了页岩储集空间划分方案,将研究区龙马溪组页岩储层储集空间划分为无机孔、有机孔、裂缝三个大类。结合页岩成岩过程,考虑机械压实、热演化机制、黏土矿物转化、溶蚀作用等因素,定性探讨了页岩储层孔隙的形成演化过程。研究区龙马溪组页岩储层主要储集空间为黏土集合体内矿片间孔隙、黏土絮体间孔隙、粒内有机质纳米孔及裂缝。有机质纳米孔隙是页岩演化到一定阶段的产物,并不是所有页岩储层中都会发育有机质纳米孔隙,且有机质纳米孔的形成和保存受多种因素的影响。

Study of shale reservoir space is one of the core contents of shale oil and gas,and shale pores have a great influence on the reservoir capacity and the percolation feature of the reservoir.Microscopic analyses of thin sections,scanning electron microscopy,focused ion beam milling（FIB）,field emission SEM（FE-SEM）and Energy Dispersive Spectrometer（EDS）were used to determine the genesis,size,morphology,distribution,connectivity of the Longmaxi shale reservoir in the study area.Based on the genesis of reservoir space and the developing positions of the pores,classification of the reservoir space was analyzed.The reservoir spaces of Longmaxi shale in the study area are divided into inorganic pores,organic pores and fractures.According to the diagenesis process of the shale,mechanical compaction,thermal evolution mechanism,clay mineral transformation,dissolution were considered to qualitatively discuss the formation and evolution process of the reservoir spaces.The reservoir spaces of the Longmaxi shale in the study area mainly include pores between clay mineral platelets,clay floc pores,pores within organic matter and fractures.Organic matter pores are the products of shale evolution to a certain stage,and not all the shale reservoir develop organic matter nanometer pores.The formation and preservation of organic matter nanometer pores are influenced by various factors.