Reservoir Geomechanics Workflow in Underground Coal Gasification

Jack Deng and Daiming Li
Supervisor: Dr. John Chen

analytical and numerical

Thermal-hydrological-chemical conditions in the coal seam will be calculated using the Non-isothermal Unsaturated Flow and Transport (NUFT) code. Livermore Distinct Element Code (LDEC) code will determine the impact of those conditions (NUFT results) on the geomechanical state of stress. Changing of permeability of the coal cleat networks and fracture networks in the caprock/bedrock will affect the stability of the cavity roof, which results in failure of the coal and the overlying caprock. LDEC calculated perturbations will be looped back by the NUFT code and forms the iterative computational process until a converged solution being obtained.

This research can be generalized as firstly analytical model validated by the lab experiments; secondly, CMG Stars + Geomechanical module (built-in); third, Coupled Geomechanical modeling of subsidence (CMG + Abaqus); forth,Geomechanical coding for UCG (subsidence and Spalling). Conclusively, UCG geomechanical modeling workflow is established; based case model using CMG non-linear geomechanical modeling approach is accomplished; CMG+Abaqus platform for coupled geomechanical modeling of subsidence has been setup. Their future work includes accuracy of the UCG constitutive model, ensuring the consistence of the geo-mechanical model with physics of the cavity growth, and history matching with lab experiments and field production data.