注气驱替煤层瓦斯时效特性影响因素分析

Influencing factors on time-varying characteristics of displacement coalbed methane by gas injection

为了分析注气驱替煤层瓦斯时效特性的影响因素,建立了注N2驱替煤层瓦斯的数学模型,采用COMSOL Multiphysics软件模拟了注气压力、抽采负压和注气时间对注气驱替煤层瓦斯时效特性的影响,研究了不同条件下煤层瓦斯含量和消突周期的变化规律,结果表明：注气压力越大,瓦斯含量下降越快,消突周期越短,合理的注气压力为0.5 MPa;抽采负压对其时效特性的影响不大,合理的抽采负压为5~13 kPa;煤层瓦斯含量随着注气时间的增加逐渐下降,注气孔附近为注气驱替煤层瓦斯的薄弱区域。在石港公司进行注气驱替煤层瓦斯现场试验,通过与数值模拟结果的对比得出：在相同的条件下,实测的瓦斯含量总是略小于模拟结果,并对造成这种差异性的原因进行了分析。

In this paper,to analyze the influencing factors on time-varying characteristics of displacement coalbed methane by gas injection,the mathematical model of displacement coalbed methane technology by N2 injection was established,and the effects of the influencing factors,such as gas injection pressure,drainage negative pressure,gas injection time,et al,on the time-varying characteristics of displacement coalbed methane by gas injection have been simulated by using COMSOL multiphysics software,then the variation laws of the methane content and outburst elimination cycle under different conditions were studied.The results show that the greater the gas injection pressure is,the faster the methane content decreases,and the shorter the outburst elimination cycle is,while the reasonable gas injection pressure is 0.5 MPa.In addition,the influence of drainage negative pressure on the time-varying characteristics is not obvious,and the reasonable drainage negative pressure is 5-13 KPa.Moreover,the methane content decreases gradually with the increase of injection time,while the position near the gas injection borehole is the weak area in the displacement coalbed methane technol ogy by gas injection.Furthermore,the field tests were carried out in Shigang Company.By comparing with the numerical results,the measured methane contents are always slightly smaller than that in simulation results under the same conditions.The reasons for this difference were also analyzed.