Abstract:

Although there are series of strata with gasbearing shale in Guizhou Province, the main work was focused on the black shale of Cambrian and Silurian systems instead of the Upper Permian Longtan Formation. In order to make up such shortage, the black shale of the Upper Permian Longtan Formation in the northwest of Guizhou Province was studied by the Xray diffraction mineral analysis of whole rock, by the tests of surface area, TOC and Ro, and especially by the field emission scanning electron microscopy. The average content of quartz is 47.8% with the highest content in the middle and south of Dafang County, and clay minerals is 41.4%, which decreases first then increases from north to south. The researched pores are mainly mesopores and have a periodic trend from north to south. A classification, consisting of three major pore types, i.e., interparticle pores, intraparticle pores and organicmatter pores, is presented. It is worth mentioning that organicmatter pores are abundant and of great importance. With increasing TOC, micropore volumes relatively increase. The volumes of mesopore increase with a greater sum of clay minerals. And quartz contributes to the sum of macropores. Thus qualitative observation by the field emission scanning electron microscopy verified the quantitative experimental analysis.

Key words:  pore types, pore volume, black shale, Longtan Formation, northwest of Guizhou