煤岩孔隙度主控地质因素及对煤层气开发的影响

为系统分析煤岩孔隙度主控地质因素及对其煤层气开发的影响，统计分析了全国37个主要煤层气区块/矿区的压汞孔隙度等数据。利用相关趋势分析方法分煤级着重探讨煤级、煤体结构、镜质组、灰分等因素对煤岩孔隙度以及煤层气开发的影响。结果表明:Ro,max是储层物性评价的重要参数，低煤级区煤岩孔隙度对Ro,max的变化最为敏感，且孔隙度平均值随成熟度升高呈现出高-低-高-低的变化。低煤级区同一煤层气区块/矿区内部，孔隙度变化区间大于高煤级区同一煤层气区块/矿区内部孔隙度的变化区间。中低煤级区，复杂的煤体结构对煤储层物性具有破坏作用；高煤级区，复杂的煤体结构对物性有一定的改善作用。镜质组含量与孔隙度呈负相关关系，灰分产率与孔隙度无明显相关性，且在低煤级区镜质组含量和灰分产率与孔隙度均具有明显的负相关性，是孔隙度评价的重要参数；而在中高煤级区，二者对孔隙度的影响可以忽略。煤岩大中孔比例和储层平均渗透率随平均孔隙度的增高而增高，孔隙度大小尤其是孔隙度随煤级的变化规律对不同煤级区煤层气开发潜力评价具有重要指导意义。

Geological Controlling Factors of Coal Pore System and Its Significance in CBM Development

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,max is 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.