超临界CO_2驱替煤层CH_4装置及试验研究

自主研发了MCQ-Ⅱ型大试件(100mm×100mm×200mm)超临界CO2驱替煤层CH4试验装置,该装置不仅能够保障试验过程中CO2始终处于超临界状态,而且可测量煤体吸附过程中的体积膨胀。借助本装置对同一温度不同体积应力条件下的超临界CO2的渗透性及其驱替CH4效果进行了试验研究。试验结果表明:在50℃、恒定体积应力为48~60MPa条件下,超临界CO2的渗透率与注入渗透压呈正相关关系,与体积应力呈负相关关系。超临界CO2在煤体中的渗透特性远远高于其在常态条件下的渗透性。试验同时发现,超临界CO2在煤体中的吸附量与孔隙压力及体积应力均呈正相关,在48和60MPa的体积应力下,单位体积的煤体分别可累计吸附10.82~17.52体积和16.12~20.40体积的CO2;试验还测得了不同条件下煤体吸附CH4、超临界CO2及超临界CO2驱替煤体CH4过程中,煤体体积膨胀百分比。在超临界CO2驱替CH4试验中,2号焦煤煤样试件中注入气体体积(包括CH4,CO2)均小于1号弱黏煤煤样,但是两煤样中的CO2/CH4置换比及CO2最终储存率相当,分别为4.01/4.16,20.05%/20.09%。

Experimental study on coal bed methane displacement and recovery by super critical carbon dioxide injection

A new experimental equipment MCQ-Ⅱfor supercritical CO2-ECBM recovery test with large size specimen was designed.The equipment can measure the specimen swelling during the supercritical CO2-ECBM recovery test.With the equipment，series of experiments for supercritical CO2 seepage and CH4 recovery with supercritical CO2 displacement were carried out.It is found that，under the conditions of 50 ℃ and constant volumetric stress，supercritical CO2 permeability is positively related to the infiltrating pressure，while it is negatively related to the confined volumetric stress.It turns out that supercritical CO2 permeability in the coal is higher than CO2 in general condition.The rise of volumetric stress and pore pressure will increase the supercritical CO2 adsorption.Under 48 MPa and 60 MPa volumetric stress，10.82 to 17.52 and 16.12 to 20.40 units of carbon dioxide can be stored in per unit of coal，respectively.During the process of CH4 adsorption，CO2 adsorption and CH4 displacement by CO2，coal swelling volumetric percentage is recorded.In the experiment of CH4 displacement by supercritical CO2，more CH4 and CO2 were injected to specimen No.1(weakly caking coal) than specimen No.2(coking coal)，but the replacement ratio of carbon dioxide to methane and the CO2 storage rate are almost equal，4.01/4.16，20.05%/20.09%，respectively.