不同应力水平下煤的渗透率演化规律研究

在煤钻进时,井周裂隙发育,钻井液易侵入井周附近地层,影响井周应力分布。准确确定不同应力水平和损伤程度下的煤渗透率是定量计算煤井壁损伤区应力变化,进而分析煤层井壁稳定性的关键。针对长畛矿3#煤,利用MTS816电液伺服岩石试验系统进行不同渗透水压和围压条件下的全应力-应变过程渗流特性试验研究,测定了煤渗透率随应力水平和损伤程度的变化规律。根据分析结果,将渗透率随加载应力增加的变化分为两个阶段:稳定下降阶段与急速上升阶段,建立了煤的渗透系数演化方程;并印证了推导的理论曲线能很好地对应实验结果。

The study on coal permeability evolution law under different stress levels

While drilling in the coal bed, fractures develop near the borehole, which can affect the area stress distribution. The research of the stress sensitivity of coal permeability is the basis for the calculation of stress variation in damage zone and borehole stability analysis. For 3# coal in CHANGZHEN coalfield, the permeability test of which in the stress-strain process is carried on the MTS816 Servo-controlled Rock Mechanical Test System. According to the analyzed results, the variation of permeability with loading stress is divided into two stages: descent stage (elastic stage) and ascent stage (abrupt stage). The evolution equation of coal permeability coefficient is established. The whole process can be expressed by the piecewise function, and calculation shows the theoretical curve fits the records well.