Underground Coal Gasification (UCG) is a process in which coal is converted to syngas in-situ. UCG has gained popularity recently as it could be used to extract energy of deep-lying coal seams, and it reduces the footprints attributed to the gasification process. In this study, two models have been developed to describe UCG process under in-situ conditions. Initially, a two-dimensional model was developed in COMSOL Multiphysics. Results and limitations of this model are discussed. The second model was developed in ANSYS FLUENT which includes all relevant reactions in a three-dimensional geometry. A detailed sensitivity analysis has been performed to investigate the effect of various parameters on the performance of the process. The results indicated particular importance of coal properties and variation of these properties with temperature. This study provides a strong basis for further extension of the model to the larger scales.