基于微流控技术的裂隙水侵特征可视化研究

Imaging dynamic water invasion behavior in microfractures based on microfluidics

煤岩裂隙中的流体侵入广泛存在于地下工程中。为明确裂隙中流体的微观动力学行为,利用三维形貌仪获得了苏拉特盆地煤的微米级裂隙,通过Stitching算法重建完整的裂隙网络结构,并通过微流控技术批量制作表征裂隙结构的透明模型。利用多相流体显微成像系统可视化不同流速、润湿性条件下的流动过程,捕捉水相在微裂隙模型中完整的侵入过程。高流速可以促进水相侵入开度较小的分支通道,气水前缘保持较小的曲率削弱了滞后效应的影响,突破发生后可进一步增强在盲端、封闭结构中的侵入程度,突破后的含水饱和度增长较快。润湿性的转变影响水相侵入过程优势通道的选择,疏水环境中水相侵入突破时间短,较大的表面张力导致滞后效应的影响显著。突破后水相可继续侵入连通通道,但在封闭通道中的入侵率极低。研究成果对岩体非饱和条件下的岩-气-液作用机制具有重要的指导意义。

Fluid invasion through fractures is frequently observed in subsurface engineering. To elucidate the microkinetic behavior of fracture fluids, the microfracture structure of coal from the Surat Basin was reconstructed using a 3D morphometric system and stitching algorithm, then the transparent models characterizing the fracture structure were produced using microfluidics, and water invasion in the microfracture model was measured via visualization experiments under various conditions. High flow rate facilitated the invasion of the water phase into the closed channel, improving the efficiency of water invasion in the neutral wetting system. Wettability reversal changed the dominant channel for water invasion in the hydrophobic system. The invasion efficiency in closed and small aperture bypass channels was low.The reduction of effective seepage channels led to the fastest breakthrough time. Higher surface tension and interfacial curvature promoted the hysteresis effect. The reduction of effective seepage channels led to the fastest breakthrough time. The larger surface tension and interfacial curvature make the hysteresis effect more significant. These results will enable a better understanding of the rock-gas-liquid multiphase interaction mechanisms under unsaturated conditions of rocks.