低渗透煤层注入超临界二氧化碳渗透性试验研究

为了提高低渗透煤层中煤层气的采收率,利用煤岩体典型的双重介质结构特征和超临界CO2具有表面张力为零、粘度低、扩散度和溶解能力强的特性,对超临界CO2注入低渗透煤层煤样的渗透性规律进行试验研究。结果表明：在超临界状态下,煤样渗透率和渗透系数均随有效体积应力的增大呈负指数递减；渗透率随孔隙压力的增大呈指数变化规律,趋势受粘度和孔隙压力之间关系的影响；渗透系数随孔隙压力的增加呈正指数递增规律；渗透率和渗透系数均随温度的升高呈负指数降低规律。此外,在注入超临界二氧化碳后,煤样的宏观和微观上均发现大量网状裂隙带和孔隙带,对提高低渗透煤层渗透性具有良好的效果。

Experimental Study of Supercritical Carbon Dioxide Permeability in Low Permeability Coal Seam

In order to enhance coalbed gas recovery in low permeability coal seam, seepage experiments were carried out for supercritical carbon dioxide in coal samples of low permeability coal seam based on double-medium characteristic of coal mass and zero surface tension, strong diffusion degree, low viscosity, and strong dissolving ability of supercritical carbon dioxide. The results show that under the supercritical condition, there is a negative exponential decrease relation between permeability and permeability coefficient of coal samples and effective volume stress. There is an exponential relation between permeability and pore pressure. The relation is controlled by relation of viscosity and pore pressure. There is a positive exponential increase relation between permeability coefficient and pore pressure. There is a negative exponential decrease relation between permeability and permeability coefficient and temperature. In addition, with a supply of supercritical carbon dioxide, a large number of mesh fissure zone and pore zone can be found in the coal samples on macro and micro point and contribute to improve permeability of low permeability coal seam.