CO₂ interaction causes complex mechanical deformations and flow modifications in coal, depending on the spatial disposition of the fracture-matrix system. Sorption-induced matrix swelling reduces the local fracture aperture and correspondingly the fracture permeability, consequently influencing gas flow throughout the seam. Since these modifications are highly -heterogeneous and -localized, an explicitly-represented geometric model is essential for the accurate modelling of the fully-coupled process. In this study, the CO₂ flow – coal deformation process is implemented in a numerical model at the scale of coal constituents (i.e. matrix blocks and cleats), through the inclusion of a spatially distributed 3D – discrete fracture matrix (DFM) network. Fracture geometry is generated from a stochastically simplified 2D fracture network obtained from micro-CT imaging. The approach is initially validated against experimental results from a single-fractured coal specimen and the analysis extended to the complex fracture geometry. The spatial and temporal evolutions of fracture/matrix pressure, adsorbed mass of CO₂, adsorption-induced swelling, alterations in local fracture aperture and permeability, and contact modelling at fully fracture closure are specifically analysed with comparison against no-swelling behaviour. Results indicate that the high-permeability fracture pathways provide initial easy access for the CO₂ to diffuse into the coal matrix, causing sorption-induced matrix swelling. Although the individual matrix blocks exhibit a slight shrinkage immediately upon injection of high fluid pressures within the fractures, sorption-induced swelling rapidly overcomes this, resulting in an overall volume expansion at full pressure equilibration. This is turn causes a significant reduction in fracture aperture and permeability. The magnitude of the local fracture aperture reduction depends on the swelling behaviour of the bounding matrix, that leads to essentially full-closure of small fractures, causing significant localized flow modifications to further CO₂ injection in the vicinity of the particular fractures. The contact modelling approach identifies the timing and locations of fully-closing fractures in the complex geometry, where butt cleats exhibiting initial small apertures are prone to fully-close, compared to larger aperture face cleats that retain flow.

CO ₂相互作用会导致煤中复杂的机械变形和流量变化，具体取决于裂缝基质系统的空间布置。吸附引起的基体膨胀减小了局部裂缝的孔径，并相应地降低了裂缝的渗透率，因此影响了整个煤层的气流。由于这些修改是高度异质且局部化的，因此对于完全耦合过程的精确建模，显式表示的几何模型必不可少。在这项研究中，CO ₂通过包含空间分布的3D-离散裂缝矩阵（DFM）网络，以煤成分（即基质块和割理）的规模在数值模型中实现了流-煤变形过程。裂缝的几何形状是通过从微型CT成像获得的随机简化的2D裂缝网络生成的。该方法最初是根据单裂煤样品的实验结果进行验证的，并且分析扩展到了复杂的裂隙几何形状。裂缝/基质压力，CO ₂吸附质量的时空演化，与非溶胀行为进行比较，专门分析了吸附引起的溶胀，局部裂缝孔径和渗透率的变化以及完全裂缝闭合时的接触模型。结果表明，高渗透性裂缝通道为CO _2的初步进入提供了便利扩散到煤基质中，引起吸附引起的基质膨胀。尽管各个基体块在裂缝中注入高流体压力后立即显示出轻微的收缩，但是吸附引起的溶胀迅速克服了这一点，从而导致了在全压力平衡下的整体体积膨胀。进而导致裂缝孔径和渗透率的显着降低。局部裂缝孔径减小的幅度取决于边界矩阵的膨胀行为，从而导致小裂缝基本上完全闭合，从而导致局部局部流向其他CO _2的明显改变。在特定骨折附近注射。接触建模方法确定了复杂几何形状中完全闭合裂缝的时机和位置，与保持流动的较大孔径的表面楔相比，初始初始小孔的对接楔易于完全闭合。