双向脉冲法渗流模拟试验及其影响因素分析

Permeability determination of rock mass—numerical analysis of bidirectional pressure pulse test

瞬态法广泛用于致密岩体渗透率测量。传统瞬态法由于忽视储层压缩性及气体吸附性对渗透率的影响,在测量页岩、煤等有机质岩体渗透率时会产生较大误差。本文通过TOUGH+REALGASBRINE模拟了瞬态法试验,研究了孔隙率、容器体积及吸附参数对渗流影响。研究结果表明,孔隙率较小或容器体积较大时,储层压缩性对传统脉冲法渗流影响可忽略;气体吸附性对传统脉冲法渗流影响较大,采用吸附性气体对页岩和煤等岩体进行渗透率测量时应考虑吸附影响。双向脉冲法能有效消除储层压缩性及吸附性对岩体的渗透率测量影响,且压力梯度能较早的达到常数,比传统脉冲法更为适用。

Pressure pulse decay is a widely used method for permeability estimation of tight rock. However,permeability errors of shale and coal,which include organic matter,will be induced when using traditional pressure pulse decay method due to storage compressibility and gas adsorption effects. In this paper,pressure pulse decay method is analyzed numerically through TOUGH + REALGASBRINE. The effects of porosity,chamber volume and adsorption parameters on permeability are researched. The results show that the influence of storage compressibility on permeability obtained from traditional pressure pulse decay method is negligible at low porosity or big chamber volumes. Adsorption effects have a significant influence on permeability,and should be considered when testing permeability of adsorptive rock like shale and coal. Bidirectional pressure pulse decay can eliminate the influence of storage compressibility and gas adsorption on permeability effectively. Moreover,pressure gradient becomes a constant at an early time,indicating that the bidirectional pressure pulse decay is more applicable than the traditional method.