Characteristics of the pore-microfracture system of coal reservoirs in Enhong area, Yunnan province

As the largest medium and high volatile bituminite coalfield in Yunnan province, Enhong area is rich in CBM resources. Employing multiple testing methods, such as mercury intrusion porosimetry (MIP) and liquid nitrogen adsorption, this paper described the pore-microfracture system of the coal reservoirs in Enhong area, analyzed the characteristics of the porosity and permeability, and studied the influencing factors of porosity and permeability. Results showed that:the coal reservoirs in Enhong area have big thickness and medium coal metamorphism, micropores and transition pores are well developed, which are favorable for the methane sorption. The structure of the seepage pores is simple, and the permeability is relatively good with weaker heterogeneity. Mimicrofractures are dominated by type D, which have poor directivity and connectivity that may result in the decrease of permeability, and is not favorable for the further development of the CBM.