超临界CO_2作用时间对煤渗透率和孔隙率的影响规律研究

The influence law of action time by supercritical CO_2 on permeability and porosity of coal

为研究超临界CO_2作用后煤渗透率和孔隙率的变化规律,在超临界CO_2增透实验基础上进行了微观成像实验,提取煤微观孔隙特征,计算孔隙率,得到了煤孔隙率和渗透率变化的等值线图。结果表明:经超临界CO_2作用后,煤的渗透率较作用前提高了一个数量级,并随超临界CO_2作用时间的延长呈正指数增加,当作用时间为20h时,煤的渗透率较增透前提高了20.2倍;随超临界CO_2作用时间的增加,蜂窝状孔隙逐渐向更为细小的颗粒空间发展,孔隙数量明显增加。增透煤微观孔隙定量结果显示,随着超临界CO_2作用时间的增加,孔隙率等值线密集程度增加,煤各微区孔隙逐渐发育,孔隙率增加,当作用时间增加到20h时,孔隙率较增透前提高了17.20倍。煤的渗透率随孔隙率的增加呈正指数递增,说明宏微观结果是一致的,超临界CO_2增透促进了煤微观结构的有效发育,提高了煤的渗透率。

In order to study the change law of coal permeability and porosity after the action of super-critical CO_2, the micro imaging experiments are carried out on the basis of macroscopic super-critical CO_2 enhancement experiment, the micro pore characteristics of coal are extracted, the porosity is calculated and the isoline maps of porosity and permeability of coal are obtained. The results show: after the action by super-critical CO_2, the permeability of coal increases by an order of magnitude than that before action, and presents the positive increase exponential trend with the increase of the action time by the super-critical CO_2, the permeability of coal has been increased by 20.2 times than that before enhancement experiment when the action time is 20 h. With the increasing of action time by super-critical CO_2, the honeycomb pores develop into finer particles and the number of porosity increases obviously. The micro-pore quantitative results of enhancement coal show, with the increase of action time by super-critical CO_2, the dense degree of porosity isoline increases, the pores of each micro area in the coal develop gradually and the porosity increases, when the action time increases to 20 h, the porosity increases by 17.20 times than that before the enhancement experiment. The permeability of coal presents the positive exponential increase with the increase of micro porosity, which illustrates the macro and micro results are consistent, the super-critical CO_2 promotes the effective development of the micro-structure of coal and improves the macroscopic permeability.