摘要:
现有的CO2驱替置换CH4研究大多针对微观的注气驱替机理和宏观的驱替置换效率影响因素方面，且多为模型层面的理论分析或模拟试验层面的多因素分析，具有针对性的物理模拟试验及量化分析较少。针对上述问题，利用注CO2气体驱替煤层CH4试验系统，研究了不同注气压力下的驱替过程中煤体内CO2驱替CH4的渗流扩散演化规律和时变特性，分析了全过程中出气口CO2、CH4浓度、累计CH4驱替量及驱替置换比等方面的变化规律，利用物理模拟试验探究注气压力对驱替置换效率的影响规律，并进行了量化分析。试验结果表明：① 不同注气压力下的CO2、CH4气体浓度变化趋势基本一致，可划分为原始平衡阶段、动态平衡阶段和新平衡阶段3个阶段，随着注气压力依次增大，CO2、CH4气体打破原始平衡阶段的时间逐渐缩短，动态平衡阶段时间增加，而新平衡阶段的时间大致相同。② 不同注气压力下，累计CH4驱替量随着注气时间的增加而增加，增加速率先快后慢，最终趋于定值。注气压力由0.6 MPa升至1.4 MPa，累计CH4驱替量增加，驱替置换比由4.99降至4.10，即驱替置换单位量CH4所需吸附的CO2量减少，驱替置换效率提升。注气压力为1.4 MPa时驱替置换比最小，驱替效率最好。该结论可为低渗透性煤层开展CO2-ECBM相关技术理论研究及现场技术实施中注气压力参数的选取提供参考。
Abstract:
Most of the existing studies on CO2 replacement for CH4 are focused on microscopic gas injection replacement mechanism and macroscopic replacement efficiency influencing factors, and most of the studies are theoretical analysis at the model level or multiple factor analysis at the simulation test level. There are few physical simulation experiments and quantitative analysis. In order to solve the above problems, by using CO2 replacement for CH4 experiment system, this paper studies the seepage diffusion evolution law and time-varying characteristics of CO2 replacement for CH4 in coal during the replacement process at different injection pressures. This paper analyzes the change law of CO2 and CH4 concentrations at the gas outlet, the accumulated CH4 replacement volume and the replacement ratio during the whole process. Physical simulation experiments are used to investigate the influence of gas injection pressure on the replacement efficiency and make the quantitative analysis. The experiments results show that: ① The CO2 and CH4 gas concentration change trends at different injection pressures are basically the same, which can be divided into three stages, including the original equilibrium stage, the dynamic equilibrium stage and the new equilibrium stage. As the gas injection pressure increases, the time of CO2 and CH4 gas breaking the original equilibrium stage is gradually shortened, the time of the dynamic equilibrium stage increases, and the time of the new equilibrium stage is about the same. ② At different injection pressures, the accumulated CH4 replacement volume increases with the increase of gas injection time, and the increase rate is fast at first and then slow, and becoming a fixed value at last. The gas injection pressure increases from 0.6 MPa to 1.4 MPa, the accumulated CH4 replacement volume increases, the replacement ratio decreases from 4.99 to 4.10, and the replacement efficiency increases. When the gas injection pressure is 1.4 MPa, the replacement ratio is the smallest and the replacement efficiency is the best. This conclusion can provide a reference for the theoretical study of CO2-ECBM related technologies and the selection of related process parameters for technical implementation in low permeability coal seams.
百度学术
下载:
