低渗透气藏气体渗流机理实验

EXPERIMENT ON GAS SEEPAGE MECHANISM IN LOW-PERMEABILITY GAS RESERVOIRS

针对低渗透气藏含水饱和度较高的特点,改进了气体渗流实验方法,在提高了实验精度的基础上,结合平均压力梯度下气体流速的实验数据处理方式,发现了转折型气体渗流曲线类型——在不同实验压差区域内其气体渗流规律不同,即随压力梯度的增大,阈压效应与滑脱效应依次占主导地位。在此基础之上,通过进一步的实验研究,分析了常压状态与覆压状态下低渗含水岩心中气体渗流特征的差异。研究认为,转折型气体渗流曲线是滑脱动力与毛细管阻力这两种相互制约、相互矛盾的影响因素此消彼长的宏观体现,而拐点的位置反映了两种影响因素主导地位的转化界限。

In view of low-permeability gas reservoir's relatively high water saturation,the experiment method of gas seepage is modified;on the basis of raising the experiment accuracy and combining the experimental data handling method of gas circulation velocity under average pressure gradient,a kind of turning point-type gas seepage curve is discovered,the gas seepage pattern is not same in the different experimental pressure drop area,that is with the augmenting of pressure gradient threshold pressure effect and slippage effect takes the dominant position in turn.On this basis,the differences of gas seepage characteristics under normal pressure and overlay pressure in low seeping water-contented rock core are analyzed by means of further experimental study.The research result is that turning point-type gas seepage curve is the macroscopic manifestation of the two influential factors restraint and contradict each other,i.e.,slipping force and capillary resistance force;and the location of turning point reflects the transformation border of the two influential factors' dominant position.