泥页岩中黏土矿物纳米孔隙结构特征及其对甲烷吸附的影响

Characteristics of nano-pore structure of clay minerals in shale and its effects on methane adsorption capacity

查明黏土矿物纳米孔隙结构特征及其对甲烷吸附的影响,对认识页岩气的赋存和运移产出具有重要意义。针对蒙脱石、伊利石和绿泥石页岩中主要黏土矿物,开展了低温液氮吸附和甲烷等温吸附实验研究。结果表明:(1)黏土矿物孔隙结构复杂,主要由纳米孔组成,孔径2~50 nm的孔隙提供了主要孔隙体积和比表面积,蒙脱石、伊利石和绿泥石中孔分别占到孔隙总体积的81.45%,71.34%和75.36%,比表面积的88.70%,87.70%和90.65%,中孔(2~50 nm)孔隙构成甲烷气体赋存的重要空间。(2)矿物主要发育平行板状的狭缝型孔隙,同时含有少量的墨水瓶形孔。(3)不同黏土矿物气体吸附能力差异明显,蒙脱石、伊利石和绿泥石最大吸附量分别为8.80,3.27和2.69cm3/g。黏土矿物对甲烷吸附主要受控于矿物的中孔比表面积,最大吸附量与矿物的中孔比表面积大小具有强烈的正相关性。

It is important for understanding the occurrence and migration output of shale gas to find out the pore structure characteristics of clay minerals and their effects on methane adsorption.This paper focuses on the study of low temperature liquid nitrogen and isothermal adsorption of methane based on montmorillonite,illite and chlorite in shale.The results show that：（1） The clay mineral pore structure is complex,which is mainly composed of nanopores,and the pore aperture 2-50 nm provides the main pore volume and surface area. In detail,the mesoporous of montmorillonite,illite and chlorite respectively accounted for 81.45%,71.34% and 75.36% of the total pore volume and 88.70%,87.70%and 90.65% of specific surface area.The hole（ 2-50 nm） pore constitute an important space of methane occurrence.（2） Clay minerals mainly develop the slit pores in parallel plate with small amount of ink bottle holes.（3） The difference between the gas adsorption capacity of distinct clay minerals is obvious,and the maximum adsorption amount of montmorillonite,illite and chlorite is 8.80,3.27 and 2.69 cm-3/g respectively.Clay minerals on methane adsorption is mainlycontrolled by the specific surface area of minerals,the maximum adsorption capacity and mesoporous specific surface area of clay minerals have a strong positive correlation.