Geological Controlling Factors of Coal Pore System and Its Significance in CBM Development
LIU Na;KANG Yongshang;LI Zhe;WANG Jin;SUN Liangzhong;JIANG Shanyu;College of Geosciences,China University of Petroleum;State Key Laboratory of Petroleum Resources and Prospecting;
To systematically analyze the key geological controlling factors of coal pore system and the significance for coalbed methane development,we present new statistical data for the mining area of 37 major CBM blocks/mercury,and use the trend analysis method to clarify the coal rank,coal body structure vitrinite and ash effect coal porosity,and the significance of porosity research for coalbed methane development. Our results suggest that Ro,maxis an important parameter for reservoir property evaluation,and that coal porosity in low rank area is most sensitive to Ro,max. Besides,the average porosity shows successive peaks and troughs with increasing coal maturity. The range of porosity in the same coalbed methane block/mining area of low rank is wider than that of high rank. Complex coal body structure has a destructive effect on the coal reservoir properties,whereas the high coal rank region and complex coal structures are beneficial to the properties; Vitrinite content is negatively correlated with porosity,and no obvious correlation is found between ash content and porosity. In the low coal rank region,vitrinite and ash content have obvious negative correlation with porosity,whereas the effect on the porosity is negligible in the high coal rank region. The proportion of meso/macro-pores and average permeability increase with increasing average porosity and porosity size. In particular,the changes of porosity with the coal rank in different areas have important guiding significance for the coalbed methane development.