Abstract
Geological sequestration of CO(2) in coal seams is one of the effective methods to reduce carbon emissions. However, the combined effects of evolving CO(2) viscosity and the inherently low permeability of coal reservoirs can significantly inhibit CO(2) flow capacity, thereby affecting the overall storage efficiency. The dynamic dual-control mechanisms governing CO(2) migration in coal seams remain insufficiently understood. The analysis of dynamic dual-control weights influencing CO(2) flow behavior is focused on in this study. On this basis, a mathematical model is developed and numerical simulations are conducted. The model captures the transient evolution of CO(2) viscosity and the permeability of coal seams during the sequestration process and investigates the coupling relationship between CO(2) properties and coal seam permeability. Two mathematical decomposition methodsthe logarithmic decomposition method and the finite difference decomposition methodare employed to perform parameter decoupling analysis of CO(2) migration in coal seams. The dynamic coupling characteristics between permeability and viscosity are elucidated, and the dominant influence weights of their evolution on the CO(2) flow field are quantitatively evaluated. The study clarifies the stage-dependent control of fluid migration: permeability dominates initially, viscosity gains influence midstage, and both reach dynamic equilibrium over time. A dynamic dual-control weighting approach is proposed to optimize injection strategies, aiming to enhance CO(2) mobility and storage efficiency in an economically viable manner. The findings provide a theoretical basis for the accurate performance assessment of CO(2) sequestration in coal seams.