水化作用对页岩微观结构与物性的影响

Effects of hydration on the microstructure and physical properties of shale

利用场发射扫描电镜(FESEM)对水化作用前、后的页岩样品进行微观表征,通过微米CT扫描、孔隙度和渗透率测试实验来研究原始样品、饱和水及离心后样品的微观结构和物性参数之间的差异性。FESEM实验研究表明,水化作用对页岩中有机质的主体形态和位置、有机质孔隙没有影响。水化作用可增加页岩内的裂缝条数及宽度,主要表现为无机矿物之间裂缝的延伸和新裂缝的衍生、条带状有机质与无机矿物之间的裂缝宽度增加。不同含水饱和度条件下的微米CT扫描实验表明,水化作用强度受原生裂缝发育程度控制,原生裂缝越发育,水化作用越强。水化作用较强时,页岩裂缝的宽度可增加至原来的2～5倍。页岩孔隙度主要受有机质含量控制,其次受裂缝发育程度影响。页岩渗透率主要受裂缝发育程度控制,其次受孔隙度大小影响。水化作用后裂缝发育程度对孔隙度和渗透率均有影响,但对渗透率影响较大,对孔隙度影响较小。

The microstructures of shale samples before and after hydration were characterized by field emission scanning electron microscopy(FESEM),and the differences in microstructure and physical parameters of original shale samples,water saturated samples and samples with water centrifugated were examined by micro CT,porosity and permeability tests.The FESEM test shows that the hydration has no effect on the main morphology,position and pores of organic matter(OM).Hydration can increase the number and width of fractures in shale,including generation of new fractures and extension of existent fractures between inorganic minerals and width increase of fractures between banded organic matter and inorganic minerals.Micro CT results of samples with different water saturations show that the intensity of hydration is dominated by primary fracture development,in other words,the more developed the primary fractures of the shale,the stronger the hydration will be.The width of fractures increased two to five times by intense hydration.The porosity of shale is mainly controlled by organic matter content and secondly influenced by the fracture development.The permeability of shale is mainly affected by fracture development and secondly by the porosity.The fracture development influenced both porosity and permeability,but more strongly on permeability than porosity.