Sandstone and coal are the two most common types of reservoirs in nature. The permeability of sandstone in oil-bearing formations controls its oil and gas production; the permeability of the coal seam containing gas has a crucial influence on the gas drainage efficiency. One of the main factors affecting rock permeability is the spatial distribution and connectivity of pores and fissures in the rock. In this paper, a small-sized sample with a diameter of 5 mm and a height of 10 mm was used for the test. The rock samples under different stress states were scanned in real-time during the seepage testing. Based on 2D images, a 3D digital sample was reconstructed. We extracted the pores and fissures from the 3D digital sample, studied the size and distribution of the largest cluster in the sample, and revealed the influence of confining pressure and seepage pressure on the percolation probability and permeability of the sample. The research results show that brittle sandstone and plastic coal, two types of rocks with completely different properties of mechanics, have obvious differences in the spatial distribution of the largest clusters. Under the same stress state, in brittle sandstone-like rocks, the connectivity of the fissures is the primary factor affecting permeability, and the pores are the auxiliary factor; for plastic rocks such as coal, the situation is just the opposite, pores are the primary factor affecting permeability, and fissures are the auxiliary factor. The research results answer the question: Hydraulic fracturing technology can increase the oil and gas production of sandstone reservoirs but cannot increase the drainage efficiency of coalbed methane.

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基于实时显微CT的裂隙煤砂岩渗流特征试验研究及渗流分析

砂岩和煤是自然界中最常见的两种类型的储层。砂岩在含油地层中的渗透性控制着其油气产量；含瓦斯煤层的渗透率对瓦斯抽采效率有着至关重要的影响。影响岩石渗透率的主要因素之一是岩石中孔隙和裂隙的空间分布和连通性。本文采用直径5mm、高10mm的小样品进行试验。渗流测试过程中对不同应力状态下的岩样进行实时扫描。基于 2D 图像，重建了 3D 数字样本。我们从 3D 数字样本中提取孔隙和裂缝，研究样本中最大簇的大小和分布，揭示了围压和渗流压力对样品渗流概率和渗透率的影响。研究结果表明，脆性砂岩和塑性煤这两种力学性质完全不同的岩石，其最大簇的空间分布存在明显差异。在相同应力状态下，在脆性砂岩类岩石中，裂缝的连通性是影响渗透率的主要因素，孔隙是辅助因素；对于煤等塑性岩，情况正好相反，孔隙是影响渗透率的主要因素，裂缝是辅助因素。研究结果回答了这个问题：