Effect of micro-fractures on gas flow behavior in coal for enhanced coal bed methane recovery and CO₂ storage

This study investigates the impact of micro-fractures on gas flow behavior in coal formations, specifically within the context of CO₂-based Enhanced Coal Bed Methane Recovery (ECBMR). Employing comparative analysis, various gas flow models, including Unipore Diffusion Model (UDM), Bidispersed Diffusion Model (BDM), Fractal Fractional Diffusion Model (FFDM), Time-Dependent Diffusivity Model (TDDM), Anomalous Sub-Diffusion Model (ASM), and Free Gas Density Gradient Model (FGDGM), are evaluated for their efficacy in capturing the complexities. The study aims to provide insights into the accuracy and applicability of these models, considering the heterogeneity of coal seams and the influence of micro-fractures on gas flow dynamics. The major findings include the categorization of different gas flow models based on their applicability to CO₂-based ECBMR. For instance, the study suggests utilizing BDM and FFDM models while considering the heterogeneity of coal seams. Similarly using the TDDM model for time dynamics of ECBMR will give higher accuracy. The article contributes to a deeper understanding of gas migration processes in coal, particularly in the context of ECBMR, with implications for optimizing recovery strategies and addressing challenges associated with micro-fracture-induced variations in gas flow behavior.