支撑裂缝煤粉动态运移沉积可视化模拟试验研究
Experimental study on visualization simulation of coal powder dynamic migration and deposition in propped fractures
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摘要:
针对支撑裂缝中煤粉动态运移沉积过程及沉积堵塞后煤粉分布特征不明的问题，应用自主研制的煤粉动态运移沉积可视化模拟装置开展煤粉动态运移沉积模拟试验。基于试验特征图像抽提和图像像素点灰度等级识别，建立关于可视化裂缝平板长度和高度的灰度矩阵并对特征图像进行二值化处理；在二值化处理图像上划分网格，用每个网格中灰度等级为0的像素点数量（煤粉量）与网格中总像素点的比值Rc来表征煤粉沉积对支撑裂缝流动通道的影响。对比分析了不同排量、不同排驱时间煤粉在支撑裂缝不同位置处的运移、沉积、堵塞特征。试验结果表明：煤粉运移沉积主要在堆积孔隙相互连通形成的流动通道中进行，由于受重力影响，较多的煤粉沉积在支撑裂缝下缘；煤粉运移进入支撑裂缝后，将经历孔隙表面吸附、架桥堵塞孔隙吼道、滤饼堵塞流动通道3个阶段；煤粉从聚集区往裂缝出口方向运移并沿运移路径不断沉积，若不堵塞流动通道则会达到运移沉积平衡状态；煤粉沉积未造成流动通道堵塞时主要呈现出“指状沉积特征”，造成流动通道堵塞时主要呈现出“块状沉积特征”；随试验排量的增加“指状沉积特征”向“块状沉积特征”蜕化；当煤粉浓度一定且有外来煤粉持续补充时，随着排量的增加煤粉造成流动通道堵塞的几率增加且堵塞的时间提前；在排液量较大的排采初期，需要适当的控制排量减小煤粉沉积堵塞对流动通道的伤害。
Abstract:In view of the problem that the dynamic migration and deposition process of pulverized coal in propped fractures and the distribution characteristics of pulverized coal after sedimentation are blocked, the self-developed visualization simulation device for dynamic migration and deposition of pulverized coal was used to carry out simulation experiments of dynamic coal migration and deposition. Based on experimental feature image extraction and pixel gray level recognition, a grayscale matrix about the length and height of the visible crack plate is established, and the feature image is binarized. The ration of the number of pixels (the amount of coal powder) in each grid with a gray level of zero to the total pixels in the grid “Rc” is used to characterize the influence of coal powder deposition in the flow channel of propped fractures. The migration, deposition and plugging characteristics of coal powder at different positions of the propped fractures with different displacement and displacement time were compared and analyzed. The test results show that the migration and deposition of pulverized coal is mainly carried out in the flow channels formed by the interconnected accumulation pores. Due to the influence of gravity, more pulverized coal is deposited in the lower edge of the propped fracture. After the coal powder migrates into the proppant fractures, it will go through three stages of adsorption on the pore surface, bridging to block the pore roars, and filter cake to block the flow channel. Coal powder migrates from the accumulation area to the fracture outlet and deposits along the migration path. If the flow channel is not blocked, the migration and deposition equilibrium state will be reached. When coal powder does not block the flow channel, it presents “finger deposition characteristics”, otherwise it presents “massive deposition characteristics”. With the increase of displacement, the “finger deposition characteristics” tend to change to “massive deposition characteristics”. When the concentration of coal powder is constant and foreign coal powder continues to be replenished, the probability of flow channel clogging caused by coal powder increases with the increase of displacement and the blocking time will be advanced. In the early stage of drainage gas recovery, it is necessary to properly control the drainage to reduce the damage to the flow channel caused by the clogging of the pulverized coal deposition.
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期刊类型引用(5)
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