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动态的煤储层渗透率影响煤层气的开采,已引起广泛关注。针对6块采自沁水盆地南部煤矿的无烟煤样品,测试了4.3MPa围压条件下煤岩气相(氦气)渗透率变化特征,基于气体滑脱及有效应力效应分析进一步探讨了渗透率变化的控制机理。结果表明,气体压力降低过程中:①渗透率呈现“先降低后升高”的变化趋势,转折点进口气体压力约为1.9MPa(对应于平均气体压力1.0MPa);②平均气体压力小于1.0MPa时,氦气产生滑脱现象;③渗透率—有效应力之间呈近似负相关关系;④进口气体压力大于1.9MPa时,为有效应力负效应作用阶段,导致渗透率降低;进口气体压力降至1.9MPa以下时,有效应力与气体滑脱效应同时作用,此阶段气体滑脱正效应强于有效应力负效应,引起渗透率升高。
Dynamic coal reservoir permeability affects the exploitation of coalbed methane, which has aroused widespread concern. Based on the six anthracite samples collected from coal mines in the southern Qinshui Basin, the gas permeability (helium) permeability under 4.3 MPa confining pressure was tested. Based on gas slippage and effective stress effect analysis, the permeability control was further discussed mechanism. The results show that during the process of gas pressure reduction: ① the permeability shows the trend of “first decreasing then rising”, the gas pressure at inflection point is about 1.9MPa (corresponding to the average gas pressure 1.0MPa); ② the average gas pressure is less than 1.0 MPa, helium slippery phenomenon; ③ permeability - the effective stress is an approximate negative correlation between; ④ When the inlet gas pressure is greater than 1.9MPa, the effect of the negative effect of effective stress stage, leading to lower permeability; inlet gas pressure dropped to 1.9MPa below, the effective stress and gas slippage effect at the same time, this stage gas slippage positive effect is stronger than the negative effect of effective stress, causing the permeability increased.