准噶尔盆地彩南地区深层低阶煤吸附特征及其影响因素

The adsorption characteristics and affecting factors of deep low-rank coal in Cainan area of Junggar basin

现有数据表明我国1 000 m 以浅低阶煤层含气量普遍偏低,而深层低阶煤试采效果显示较好.基于Langmuir 方程开展了低阶煤高温高压环境下等温吸附模拟实验,结果表明：褐煤吸附量约占长焰煤、气煤吸附量的1/3,吸附能力最弱,随着煤阶的升高,吸附量逐渐增大;实验发现低阶煤在55℃、12 MPa 以下吸附量随温度、压力增大而增加较快,并建立了基于煤阶-温度-压力条件下的深层低阶煤饱和吸附模型;煤层随着埋藏深度的增加,吸附量呈现出快速增加-缓慢增加-缓慢递减的过程,即深层煤层吸附量存在吸附临界深度带,为1 400-1 700 m.1 400 m 以浅吸附量受压力正效应大于温度负效应,吸附量随埋深增加而增加,临界深度带内吸附量达到极限,不再增加,1 700 m 以深温度负效应大于压力正效应,吸附量随深度增加而减小.实验结果为深层低阶煤层气资源评价及开发潜力提供理论依据.

The available data show thatthe gas content of low-rank coal is generally low at the depth less than 1 000 m, however, the pilot production of gas of deeper low-rank coal has better effect. Based on the Langmuir equation, we carried out the low-rank coal isothermal adsorption simulation experiments under high temperature and high pressure. The experiment results show that the adsorption capacity of brown coal was the weakest, about a third of long-flame coal and gas coal, and adsorption quantity increased gradually with coal rank; the experiments results also show that the adsorption quantity of low-rank coal increased rapidly under 55℃ and 12 MPa, with the increase of temperature and pressure, the mathematical model for the process was established based on tempera-ture-pressure-coal rank; the adsorption quantity present the trend of fast increase-slowly increase-slowly decrease with the increase of buried depth. There exists a critical depth belt for adsorption quantity, ranging from 1 400 m to 1 700 m. At the depth less than 1 400 m, the positive effect of pressure for the adsorption quantity was greater than the negative effect of temperature, the adsorption quantity increased with the buried depth, reached the limit in the critical depth belt and increased no longer. The negative effect of temperature was greater than the positive effect of pressure at depth more than than 1 700 m, the adsorption quantity decreased with depth. The experimental results provided the theoretical basis for assessment of CBM resources and the development potential of deep low rank coal.