火山岩中脱玻化孔及其对储层的贡献

Micropores from devitrification in volcanic rocks and their contribution to reservoirs

岩相学研究表明火山岩中玻璃的脱玻化作用可以产生相当数量的微孔隙,所观察到的微孔隙为脱玻化孔和脱玻化形成的矿物与流体之间相互作用产生的孔隙之和,统称为脱玻化孔。球粒流纹岩、熔结凝灰岩中脱玻化孔是仅次于气孔的第二大孔隙类型,球粒流纹岩和熔结凝灰岩中脱玻化孔分别占相应岩石中所有类型孔隙的20%,30%左右。脱玻化孔是凝灰岩的主要孔隙类型,占凝灰岩中所有类型孔隙的70%左右。运用火山玻璃脱玻化作用的物理过程及质量平衡的原理和方法,可估算球粒流纹岩、熔结凝灰岩、凝灰岩中流纹质玻璃脱玻化作用产生的孔隙。运用流体-岩石相互作用的热力学原理和方法计算出长石溶蚀至少可以产生20 cm3/mol的孔隙。

Petrography studies show that devitritlcation in volcanic rocks can produce a considerable number of micropores. The micropores observed in volcanic rocks are a complex of mieropores from devitrifieation and that from interaction of minerals with fluids. In pyromerides and ignimbrites, micropores from devitfification are the second largest pore type after the vesicle, accounting for 20 %0 and 30 %0 of the total of all pore types in pyromeri- des and ignimbrites respectively. While in tuff,they are the predominant pore type and account for about 70% of the total pore spaces. The principles and methods of mass balance and the physical processes of devitriflcation can be used to estimate the micropores generated by devitritlcation of glass in pyromeride, ignimbrite and tuff. Calculation with the thermodynamical theories and methods of fluid-rock interaction shows that feldspar dissolution at least can produce pores of 20 cm3/mol.