也谈煤层气的液相吸附

Discussion on Liquid Phase Adsorption of Coalbed Methane

原始条件下煤层气的吸附处于欠饱和状态,开采过程中存在临界解吸现象。生产动态研究发现,煤层气在原始条件下并不符合气相吸附规律。气相吸附皆为饱和吸附,不存在临界解吸过程。煤层气的液相吸附理论不仅可以解决煤层气开发过程存在临界解吸压力的问题,而且符合煤层气的生烃环境。由于分子极性的差异,煤层气的液相吸附量大于气相吸附量。同时,煤层气开采过程中的临界解吸现象是地层水中未饱和煤层气导致的,煤层气的临界解吸压力与液相吸附系数无关,是由煤层气在水中的溶解度以及储集层条件下煤层气在水中的体积分数决定的。

The coalbed methane is in an undersaturated state under the initial reservoir condition. There exists the critical desorption incoalbed methane production. According to the production performance,it is demonstrated that the coalbed methane adsorption does notconform to gas-solid adsorption regulation. The gas-solid adsorption must be saturated,and cannot have the critical desorption process. Theliquid phase adsorption theory of coalbed methane can not only solve the critical desorption problem,but also satisfy the situation of coal-bed methane generation. Due to the difference of molecule polar,the liquid phase adsorption volume is larger than the gas phase adsorp-tion. Meanwhile,the undersaturated solution state of coalbed methane in water leads to critical desorption phenomenon. The coalbed meth-ane critical desorption pressure has no relation with liquid phase adsorption coefficient,and it is calculated by the solubility of coalbedmethane in water and the volume fraction of coalbed methane in water in reservoir conditions.