This paper introduces the development of a new predictive model in support of proppant injection in naturally fractured coal seam gas (CSG) reservoirs. In the proposed model, the finite element method (FEM) is used for the prediction of proppant embedment and elastoplastic deformation of the coal. The lattice Boltzmann method (LBM) is applied to the modelling of fluid flow through propped fractures, in which the modified partially saturated method (MPSM) is implemented to characterise the fluid–solid interactions. Permeability diagrams of the fractures are then generated as functions of particle packing ratio and effective stress. Finally, these results are incorporated into a radial Darcy flow analytical solution to predict the productivity index of the CSG wells under various proppant injection pressures and cleat compressibilities. The developed model is applied to selected coal samples from the Bowen and Surat Basins in Queensland, Australia. Modelling results indicate that proppant injection leads to increased fracture permeabilities and enhanced well productivity indexes. The elastoplastic deformation results in smaller permeability increase and less production enhancement when compared to the traditional linear elastic models. Although focused on Australian coals, the developed workflow can be broadly applicable to the assessment of potential stimulation efficacy in other unconventional reservoirs. In addition, a better understanding and implementation of the proppant injection scheme can effectively improve the post-fracturing performance, particularly in low-permeability coal intervals, which benefits the CSG industry.

本文介绍了支持在天然裂缝性煤层气 (CSG) 储层中注入支撑剂的新预测模型的开发。在所提出的模型中，有限元方法 (FEM) 用于预测煤的支撑剂嵌入和弹塑性变形。格子玻尔兹曼方法（LBM）用于通过支撑裂缝的流体流动建模，其中采用了改进的部分饱和方法（MPSM）来表征流固耦合。然后生成裂缝的渗透率图作为颗粒填充率和有效应力的函数。最后，将这些结果结合到径向达西流分析解决方案中，以预测 CSG 井在各种支撑剂注入压力和割理压缩性下的产能指数。开发的模型应用于来自澳大利亚昆士兰州 Bowen 和 Surat 盆地的选定煤样。建模结果表明支撑剂注入导致裂缝渗透率增加和井产能指数提高。与传统的线弹性模型相比，弹塑性变形导致渗透率增加更小，产量增加更小。虽然专注于澳大利亚煤炭，但开发的工作流程可广泛适用于评估其他非常规储层的潜在增产效果。此外，更好地理解和实施支撑剂注入方案可以有效提高压裂后性能，特别是在低渗透煤层段，这有利于煤层气行业。