摘要
Pores in organic-rich black shales are important hosts of gas in the rocks.Pore structures control the occurrence and distribution of shale gas.The Lower Silurian shales in south China have great potentials for shale gas.We have carried out a series of important measurements including mineral surface area,pore volume,pore diameters,total organic carbon(TOC),vitrinite reflectivity(Ro) and components of organic matter,and the abundance of detrital mineral grains and clay minerals to better understand the controls of pore volumes.The results show that the most important types of pores are mesopores with diameters varying between 2 nm and 5 nm;Mesopore volume accounts for 70% of the total volume,and micropore volume and macropore volume account for about 10% and 20%,respectively.The relationships between the pore volumes and important measured parameters such as the abundance of detrital minerals,clay minerals,TOC and Ro indicate that the abundance of clay minerals has significant control on micropore and mesopore volumes,and a dominant control on mesopore volumes.The abundance of the detrital minerals has a positive effect on macropore volumes.The occurrence of nm-scale microfractures in the organic matter with high maturity may be responsible for higher macropore volumes in the samples with Ro>2.0% and higher organic matter maturity.