Meitan xuebao (Apr 2024)
Visual physical simulation experiment of coal fines migration and blockage removal in fractures
Abstract
The deposition of coal fines in fractures can reduce the fracture conductivity and restrict the efficient and stable development of coalbed methane wells. A visual physical simulation experiment scheme for coal fines migration and blockage removal in fractures was designed. The variation of coal fines particle deposition area and sedimentary morpho-logical characteristics at different positions of fractures were analyzed and the dynamic law of coal fines migration and deposition was revealed based on the visual physical simulation experiment of coal fines migration in fractures. Using the visual physical simulation experiment of coal fines blockage removal in fractures, the influence of plugging time and flow rate on the area of deposited coal fines blockage removal in fractures was investigated and the dynamic law of coal fines starting and blockage removal was found. The experimental results show that the coal fines particles have different aggregation states in different directions and positions of the fractures. The deposition area of coal fines particles gradually decreases from the entrance to the two ends of the vertical main migration direction and the main migration direction, and the deposition area of coal fines particles gradually increases along the main migration direction in the branch channel. The morphology of coal fines deposition at the fracture throat, branch channel and main channel is eagle’s mouth shaped, layered and streamlined, respectively. The reason is that the resistance of different positions of the fracture to the coal fines-containing fluid is different, resulting in different deposition morphology of coal fines at different positions. At the same flow rate, with the increase of blockage removal time, the blockage removal effect of coal fines is better, but the area of blockage removal in the early stage is large, and the area of blockage removal in the later stage is small. The blockage removal effect of coal fines at the fracture throat is obviously better than that in the branch channel. The reason is that the loose and easy blockage removal coal fines particles will be deblocked first, and as time goes on, the remaining unblocked coal fines particles need a larger starting flow rate. The larger the flow rate is, the larger the area of coal fines blockage removal at the fracture throat and branch channel is. The reason is that increasing the flow rate can enhance the fluidity of coal fines particles.
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