页岩气储层微观孔隙结构特征及发育控制因素——以川南—黔北XX地区龙马溪组为例

Micro-pores Structure Characteristics and Development Control Factors of Shale Gas Reservoir:A Case of Longmaxi Formation in XX Area of Southern Sichuan and Northern Guizhou

利用扫描电镜以及比表面积分析仪产生的试验数据、吸附脱附曲线对页岩气储层储集空间类型、微观孔隙结构的系统研究表明,川南—黔北XX地区龙马溪组页岩气储层储集空间多样,包括残余原生粒间孔、晶间孔、矿物铸模孔、次生溶蚀孔、黏土矿物间微孔、有机质孔以及构造裂缝、成岩收缩微裂缝、层间页理缝、超压破裂缝等基质孔隙和裂缝类型。发现研究区龙马溪组泥页岩比表面积和孔体积都较大且具有良好的正相关性,并认为微孔隙越发育,泥页岩的比表面积和孔体积越大,越有利于泥页岩对页岩气的吸附储集。建立了泥页岩的孔隙模型,并利用吸附脱附曲线分析了研究区龙马溪组泥页岩的微观孔隙结构特征,指出研究区龙马溪组泥页岩以极为发育的微孔为主,其中为泥页岩提供最大量孔体积和表面积的孔隙主要为Ⅲ类细颈瓶状(墨水瓶状)孔和Ⅰ类开放透气性孔。认为有机碳含量、伊/蒙间层矿物含量以及热演化程度是控制研究区龙马溪组页岩气储层微观孔隙结构的主要因素。

It is suggested that reservoir spaces of Longmaxi shale gas reservoir in XX area of southern Si- chuan and northern Guizhou were diversified,by using of Scanning Electron Microscope （SEM）, test data and adsorption/desorption isothermal that produced from Multipoint Brunauer Emmett Teller （MBET） to do research on the types of reservoir spaces and micro-pore structure characteristics of shale gas reservoir. Reservoir spaces mainly include residual primary intergranular pores, intercrystal pores, mineral moldic pores,secondary dissolution pores, micropores among clay minerals, organic matter pores, structural frac- tures, diagenetic shrink micro-fractures, interlayer lamellation fractures, overpressure breaking fractures and so on. We found out that the pore volume and specific surface area of Longmaxi mud shale is larger and has a good positive correlation,and thought that the more developed the micro-pores were,the bigger the mud shale have the pore volume and specific surface area. It is also beneficial for mud shale to adsorb shale gas. This study established pore models of mud shale,and analyzed micro-pore structure of Longmaxi For- mation mud shale. Using adsorption/desorption isothermal, this study also proposed Longmaxi Formation mud shale mainly developed micro-pores,and argued that in those micro-pores,flask （ink-bottle） shaped pores and open air permeability pores supplied the largest pore volume and specific surface area for mud shale. We thought that organic carbon content （TOC）, the content of illite/smectite interstratified clay mineral and thermal evolution degree were the major factors to control micro-pores structure of Longmaxi Formation shale gas reservoir in XX area of southern Sichuan and northern Guizhou.