南方海相页岩物质组成与孔隙微观结构耦合关系

The coupling relationship between material composition and pore microstructure of southern China marine shale

为研究页岩物质组成与孔隙微观结构耦合关系,对南方海相五峰组—龙马溪组30个高—过成熟页岩样品开展低温氮气吸附实验,并根据迟滞回线形态划分3类页岩。结果表明:(1)黏土矿物主要发育板状孔,孔径较大,从微孔(<2nm)到宏孔(>50nm)均较为发育;有机质主要发育墨水瓶状孔,主要为微孔和介孔(2～50nm)级别。(2)页岩比表面积主要由微孔、介孔贡献,其中微孔比表面积主要由有机质提供,黏土矿物主要提供介孔、宏孔比表面积;总孔体积主要由介孔、宏孔贡献,其中有机质主要贡献微孔、介孔体积,黏土矿物主要贡献宏孔体积。(3)样品普遍具有三段分形特征,且在不同孔径范围,墨水瓶状孔均要较板状孔复杂。研究成果有助于认识页岩气的储集、运移规律。

To explore the coupling relationship between material composition and pore microstructure,30 marine shale samples with high-over maturity from the Wufeng and Longmaxi Formations,Southern China were analyzed by using nitrogen adsorption method.According to the shape of hysteresis,3types of shales are identified.The results show that clay mineral mainly develops slit pores ranging from micropore(<2nm)to macropore(>50nm),while organic matter mainly develops inkbottle pores with the size of mesopore(2-50nm).Whether in BET specific surface area(SSA)or total pore volume(PV),mesopores always makes the largest contribution.Micropores make the second largest contribution to the SSA,while macropores offer moderate PV.The SSA of microporeis mainly provided by organic matter,and clay minerals mainly contribute to the SSA of mesopores and macropores.Clay minerals mainly provide macropore volume,while organic matter mainly contributes to micropore and mesopore volume.The shale samples generally show three stages of fractal characteristics,and in the range of different pore size,the inkbottle pores are more complex than slit pores.The results are helpful to understand the law of gas accumulation and migration.