覆压下煤的孔渗性实验及其应力敏感性研究

采用沁水盆地南部煤样，通过覆压下煤的孔隙度和渗透率实验分析，建立了高煤级煤样孔隙度、渗透性与有效应力之间的相关关系和模型；采用渗透率损害率和应力敏感系数分析了高煤级煤储层的应力敏感性。研究结果表明:煤样孔隙度和渗透率随着有效应力的增加按负指数函数规律降低。在有效应力小于5或6 MPa，煤储层应力敏感系数变化较大，且煤储层应力敏感系数随有效应力增加而快速下降；渗透率损害率随有效应力的增加而快速增大，应力敏感性强；而在有效应力大于5或6 MPa时，煤储层应力敏感系数随有效应力的增加下降速度整体减缓，且存在一定波动变化，应力敏感性减弱，同时渗透率损害率随有效应力的增大而增加较为缓慢。

Experimental study on the porosity and permeability of coal in net confining stress and its stress sensitivity

The porosity and permeability of coal in net confining stress were analyzed through experiment using the coal samples in the Southern Qinshui Basin.The relationship between porosity and permeability of coal samples and effective stress and their models were established.The stress sensitivity characteristics of high rank coal reservoir was analyzed by using permeability damage rate and stress sensitivity coefficient.The results indicate that with the increase of effective stress，the porosity and permeability of coal sample decrease according to negative exponential function.If the effective stress is less than 5 or 6 MPa，the stress sensitivity coefficient of coal reservoir varies significantly，and the stress sensitivity coefficient decreases rapidly with the increase of effective stress.The permeability damage rate increases rapidly with the increase of effective stress，and the stress sensitivity of coal reservoir is enhanced.If the effective stress is greater than 5 or 6 MPa，the stress sensitivity coefficient of the coal reservoir decreases as the effective stress increases slowly，and there is a fluctuation，the stress sensitivity of coal reservoir is reduced.At the same time，the permeability damage rate with the increase of effective stress increases slowly.