低渗透岩石的单相水非Darcy流

Non-Darcy flow of single-phase water through low permeability rock

为研究低渗透岩石的非 Darcy渗流现象 ,采用FDES- 6 4 1三轴驱替评价系统进行了稳定渗流实验 ,测定了盐水和蒸馏水在低渗透砂岩和砾岩岩样中的渗流特性。岩样抽真空后水平放置于岩样夹持器中 ,通过多级驱替泵控制密闭岩样中水的渗流速度 ,所产生的压力差由压力传感器测定。结论为 :1)在空气渗透率非常低并且孔隙度非常小的砾岩中 ,明显存在着非 Darcy渗流现象 ,但由渗流曲线后退趋势所得出的启动压力梯度非常小 ,以致于在生产应用中可以忽略 ;2 )低渗透介质中的微粒运移是低速非 Darcy渗流现象存在的主要原因 ;3)岩石的非均匀性降低了岩石的渗透率。

Steady flow experiments were performed to investigate non-Darcy flow phenomenon in low permeability rocks. The FDES-641 triaxial system was used to measure the flow of brine and distilled water through low permeability saturated sandstone and conglomerates. The evacuated and then saturated rock specimens were mounted horizontally in the core-holder. The multi-speed flow-pumps maintained a constant water flow rate through the confined samples while the pressure-difference was measured. The experiments show that non-Darcy flow occurs in the conglomerate which has a very low air permeability and a small porosity, with the threshold pressure gradient determined from a regression analysis of the flow curve being so small as to be neglectable in practice applications. The migration of fine particles in the low permeability media is the main cause of the non-Darcy flow effects. The tests also show that the heterogeneity of the rock reduces its permeability for water.