3D modelling of coal deformation under fluid pressure using COMSOL multiphysics

Abstract

Gas transportation in coal bed is a complex physical process. The Adsorption/desorption process is associated with migration of gas in coal. Adsorption/desorption of CO2/CH4 in coal bed includes diffusion of gas from coal matrix and its flow through natural fractures. Therefore, it is necessary to have a clear concept of the flow behavior of gas in coal bed for successful coal bed methane (CBM) production and carbon dioxide sequestration. Flow of gas through natural cracks results in deformation of coal bed. Injection of CO2 in enhanced coal bed methane (ECBM) depends on the permeability and fluid flow behavior.Deformation in solid coal induced by fluid pressure during CBM and ECBM process is still not clearly understood. Numerical models and Multiphysics are dominant in modelling of complex study of flow induced deformation. Such modelling is required for detailed understanding of deformation as well as flow parameters. In this study 3D model of fractured coal core was developed. The deformation in coal core at multiple injected fluid pressures was analysed. Geo-mechanical parameters (Stress, Strain, Deformation, Pore pressure and Darcy's Velocity etc.) were determined at varying injection pressures. The relations between different Geo-mechanical parameters were established using a statistical approach.