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<p>The permeability of coalbed methane (CBM) reservoirs is critically controlled by the transport and clogging of coal fines within fracture networks. However, the coupled influence of flow intensity and boundary conditions (constant flow versus constant pressure) on clogging mechanisms and their evolution remains poorly understood. Herein, a semi-resolved CFD–DEM framework incorporating DLVO adhesion forces was used to simulate transport and clogging of fines in a realistic, heterogeneous fracture network derived from actual coal. Hydraulic-equivalence mapping enabled consistent comparison between constant-flow and constant-pressure regimes. The effects of flow intensity and boundary conditions were quantified based on the evolution of permeability and detailed cluster statistics, including number, size, distribution, and morphology. The results showed that flow intensity dictated the dominant clogging mechanism, while flow boundary conditions governed the post-clogging evolution of the system. Under both conditions, permeability exhibited a distinct three-stage “increase–decrease–increase” response to increasing flow intensity. These stages corresponded to a progressive transition from surface deposition with limited cluster transport, to hydrodynamic bridging induced by large throat-spanning mobile clusters, and finally to shear-driven cluster breakup into non-bridging small aggregates, promoting permeability recovery. Notably, constant-pressure operation produced self-reinforcing clogging, as flow-rate decay weakened scouring and increased particle residence time, stabilizing and densifying stationary accumulations and causing faster and deeper permeability loss. By contrast, constant-flow injection maintained flux and intensified local shear in the open channels, leading to cyclic formation–scouring–reformation of clogs and thus milder long-term damage despite stronger permeability fluctuations. This work provides mechanistic insight into coal-fines clogging and informs anti-clogging and production optimization in CBM reservoirs.</p>

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Effects of Flow Intensity and Boundary Conditions on Transport and Clogging of Coal Fines in Fracture Networks: Insights from CFD–DEM Simulations

  • 期刊论文

  • 发表日期：

    2026年5月19日

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  • Zihan Xu,
  • Fansheng Huang,
  • Shuxun Sang,
  • Shiqi Liu,
  • Zhenjiang You

摘要

The permeability of coalbed methane (CBM) reservoirs is critically controlled by the transport and clogging of coal fines within fracture networks. However, the coupled influence of flow intensity and boundary conditions (constant flow versus constant pressure) on clogging mechanisms and their evolution remains poorly understood. Herein, a semi-resolved CFD–DEM framework incorporating DLVO adhesion forces was used to simulate transport and clogging of fines in a realistic, heterogeneous fracture network derived from actual coal. Hydraulic-equivalence mapping enabled consistent comparison between constant-flow and constant-pressure regimes. The effects of flow intensity and boundary conditions were quantified based on the evolution of permeability and detailed cluster statistics, including number, size, distribution, and morphology. The results showed that flow intensity dictated the dominant clogging mechanism, while flow boundary conditions governed the post-clogging evolution of the system. Under both conditions, permeability exhibited a distinct three-stage “increase–decrease–increase” response to increasing flow intensity. These stages corresponded to a progressive transition from surface deposition with limited cluster transport, to hydrodynamic bridging induced by large throat-spanning mobile clusters, and finally to shear-driven cluster breakup into non-bridging small aggregates, promoting permeability recovery. Notably, constant-pressure operation produced self-reinforcing clogging, as flow-rate decay weakened scouring and increased particle residence time, stabilizing and densifying stationary accumulations and causing faster and deeper permeability loss. By contrast, constant-flow injection maintained flux and intensified local shear in the open channels, leading to cyclic formation–scouring–reformation of clogs and thus milder long-term damage despite stronger permeability fluctuations. This work provides mechanistic insight into coal-fines clogging and informs anti-clogging and production optimization in CBM reservoirs.