深部煤层井组注入CO2开采煤层气技术主要通过CO2的强吸附效应,能够置换出更多的CH4,同时实现CO2的长期大量的埋藏。通过试验分析,柿庄北地区CO2的吸附能力是CH4的2倍,随着解吸压力的降低,CH4比CO2会更快的解吸,能够有效的置换CH4。CO2的注入引起煤储层物性的变化,主要是由于CO2的吸附和解吸引起的基质膨胀与收缩效应造成渗透率的变化,并且呈现随着压力的降低先降低后迅速增加的变化规律。基于渗透率变化规律,应用模拟软件建立地质模型和数值模型,分析了CO2注入量、频率和注入方式对井组或单井的产量、采收率和CO2埋藏量的影响。模拟结果认为注入量10~15 t/d,连续注入90 d,关井90 d,反复实施2 a后,可以实现采收率的提高。通过现场试验验证,该区3号煤层吸附CO2的能力在8 t/d,井组的埋藏潜力约为12 616 t。

CO2 -ECBM technology in deep coal seam is that CO2 can replace more CH4 and be buried in a long-term because of its strong adsorption effect. Experimental analysis in northern Shizhuang shows that the CO2 adsorption ca- pacity is two times of CH4 . With desorption pressure decrease,CH4 has higher desorption speed than CO2 so that it can be displaced effectively. CO2 injection causes the change of the physical property of coal reservoir,mainly refers to per- meability variation caused by matrix shrinkage and swelling during CO2 adsorption and desorption,and the permeability decreases at first and increases rapidly with the decrease of pressure. By applying the permeability change rule,the ge- ological model and numerical model were established. The influences of CO2 injection quantity,frequency and injection mode on the yield,recovery ratio and CO2 burial of the well group or single well were analyzed. The simulation results show that the gas recovery increases after two years CO2 injection with the injection rules such as the injection rate of 10 -15 tons per day,continuous injection for 90 days,closing well for 90 days. Field test indicates that the CO2 adsorp- tion capacity of No. 3 coal seam is 8 tons / day. The group well burial potential is about 12 616 t.