中文摘要：

为研究CH4与CO2分子在页岩有机质中的竞争吸附机理,以四川盆地下志留统龙马溪组页岩为研究对象,基于聚焦离子束扫描电镜及氮气吸附仪的表征结果构建了分子模拟的层柱孔隙模型,利用巨正则系综蒙特卡洛法（GCMC）研究了地层温度、压力条件下有机质纳米孔隙中CH4的吸附规律,并重点研究了CO2与CH4竞争吸附的规律。研究表明：龙马溪组页岩有机质内大量发育纳米孔隙,孔隙连通性好,是吸附气重要的储集空间;温度降低、压力升高能增加CH4吸附量,地层条件下若出现超压会显著提高CH4吸附气量;CO2具有较强的竞争吸附能力,温度与压力的共同升高使CO2与CH4选择系数迅速降低,页岩气埋深越大则CO2与CH4选择系数越低。页岩气开发在流体压力下降到一定程度时再进行CO2驱替会取得较好的效果。

英文摘要：

To reveal competitive absorption behavior between CH4 and CO2 in organic matter（OM） nanopores,OM pore structure was first characterized using focused ion beam？scanning electron microscope（FIB-SEM） and pore-size distribution was studied using N2 adsorption,using Lower Silurian Longmaxi shale in Sichuan Basin as sample.Then a simplified pillar-layer model was used to study CH4 adsorption behavior and competitive adsorption effect between CO2 and CH4,using grand canonical Mote Carlo（GCMC） method.Research indicates that nanopores with good connectivity widely exist in OM,offering important storage space for absorbed shale gas.The amount of absorbed CH4 can increase with lower temperature and increased pressure,and overpressure will significantly increase the amount of CH4 absorbed underground; CO2 shows high competitive absorption ability; CO2/CH4 selectivity coefficient decreases dramatically with increasing temperature or pressure,or both,and it corresponds to deeper burial depth.CO2 EGR during shale gas exploration will be more efficient if it is conducted after the pressure drops to a certain degree.