Reconstruction of post-mining porosity-permeability field in abandoned coal mine goaf and its implication for CO2 sequestration

Abstract

The post-mining pore–fracture structure significantly influences fluid migration and storage within the goaf, yet it remains inadequately represented in most existing models. This study proposes and field-validates a mechanics-based method for reconstructing the three-dimensional porosity–permeability field of a goaf by coupling its stress and fracture fields. The method integrates an FLAC 3D stress-recovery field, obtained using an upscaled double-yield model, with a 3DEC discrete-fracture field. These fields are coupled under an orientation- and aperture-weighted fracture-tensor reconstruction through a matrix-compaction pathway constrained by mass conservation and a fracture-flow pathway based on Oda's fracture-tensor formulation. The reconstructed field reproduces the O-shaped annular permeability structure generated by the abutment-pressure arching mechanism and its pronounced vertical permeability anisotropy. A relatively stable stress-recovery plateau developed in the central goaf, with a maximum recovery ratio of 60.1%. Transport simulations show that 65%–72% of the peak CO 2 mass remains within the caved zone after 100 years of storage, with retention increasing as the height of the fractured zone decreases. By providing a mechanics-based representation of the complex and heterogeneous three-dimensional porosity–permeability structure of goafs, this study offers new insights into the spatial resource utilisation of goafs in abandoned coal mines.

The authors' abstract, as published at the source. International Journal of Rock Mechanics and Mining Sciences, 2026 · DOI ↗