单裂隙砂岩渗流特性实验研究

Experimental Research on Seepage Characteristics of Sandstone with Single Fracture

为研究裂隙对砂岩渗流特性的影响,利用激光共聚焦显微镜(LSCM)对不同粒径砂岩裂隙表面进行观测,以三维分形维数D作为裂隙表面粗糙度表征参数,采用自行研制的多功能岩石孔隙-裂隙渗流实验系统对粗糙单裂隙砂岩试件进行裂隙渗流实验,基于量纲分析法,建立粗糙单裂隙砂岩渗流模型。结果表明:三维分形维数D可以作为砂岩裂隙表面粗糙程度的表征参数。裂隙渗流流量受裂隙表面粗糙度影响较为明显,裂隙宽度相同时,裂隙渗流流量随着裂隙D的增大而减小。存在一裂隙宽度阈(b=175μm),高于该宽度值后,裂隙渗流流量迅速增长。建立了基于三维分形维数D的单裂隙渗流模型,与砂岩裂隙渗流实验结果对比,两者具有较好的吻合度,模型较为合理。

In order to study the influence of fracture on the seepage characteristics of sandstone,Laser Scanning Confocal Microscopy（ LSCM） was used to observe the fracture surface of sandstone with different particle sizes. The 3D fractal dimension D was used to characterize the fracture surface roughness. The rock pore-fracture seepage flow system was used to carried out sandstone specimen seepage experiment with different rough single fracture. And the model of sandstone seepage with single rough fracture was established. The results show that 3D fractal dimension D can characterize the surface roughness of sandstone fracture. The seepage flow of fracture is obviously affected by fracture surface roughness,and when the fracture width is same,the seepage flow decreases with the increase of fracture 3D fractal dimension D. There exists a fracture width threshold（ b = 175 μm）,and the seepage flow increases rapidly when the fracture width is greater than 175 micrometer. The model of single fracture seepage was established based on 3D fractal dimension D,the model result has good agreement with the test law of fracture seepage,so the model is reasonable.