Effect of various coal constitutive models on coupled thermo-mechanical modeling of underground coal gasification

In this study, the results from a reservoir simulator are coupled with a geomechanical module to solve for the displacement and stress variations. A controlled retracting injection point (CRIP) method is applied in the reservoir simulator to model reactions and geochemistry. By performing sensitivity analyses using the linear elastic, hyperbolic, and elasto-plastic constitutive models, the two compelling factors of high temperature and cavity evolution, which have the highest contributions to the geomechanical responses of the UCG process, are comprehensively investigated. At the end, a stress rebalancing technique is imposed on the linear elastic model to mimic the elasto-plastic solution by capturing the shear softening and the post-failure behavior of coal.