Abstract Fracture closures have direct effects on the void ratio distributions of proppant particles filled in hydraulic fractures and then influence the fluid pathways of coalbed methane (CBM) within those fractures. In this paper, a numerical simulation method was used to investigate the void ratio distributions of proppant-filled fracture under different compression amounts of 0%, 5%, 10%, 15% and 20%. The results showed that the void ratio distributions had exhibited an inverted “U” shape, with a trend of decreasing first, followed by remaining constant, and then increasing from the bottom to the top of the fracture, which could be divided into three zones: bottom loose zone (BLZ), middle compaction zone (MCZ) and top loose zone (TLZ). At the same compression, the small coordination numbers in the BLZ and TLZ had accounted for a larger proportion, and the average coordination numbers and void ratios in the two zones were 0.8–0.9 and 1.3 times than those in the MCZ, respectively. In addition, the proportion of the large coordination numbers in the different layers had increased, and the layered average coordination numbers had increased linearly, which had resulted in the layered void ratios decreasing linearly with the increases in the compression amounts.

中文翻译：

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水力裂缝闭合对煤层气储层支撑剂颗粒孔隙率的影响

摘要 裂缝闭合直接影响水力裂缝中支撑剂颗粒的孔隙比分布，进而影响裂缝内煤层气（CBM）的流动路径。本文采用数值模拟方法研究了支撑剂填充裂缝在0%、5%、10%、15%和20%不同压缩量下的孔隙率分布。结果表明，孔隙比分布呈倒“U”形，呈先减小后保持不变的趋势，从裂缝底部到顶部逐渐增大，可分为三个区域：底部松散带（BLZ）、中间压实带（MCZ）和顶部松散带（TLZ）。在同样的压缩下，BLZ和TLZ小配位数占比较大，两区平均配位数和空隙率分别为MCZ的0.8～0.9倍和1.3倍。此外，不同层中大配位数的比例增加，层状平均配位数线性增加，导致层状空隙率随着压缩量的增加而线性降低。