Underground coal gasification (UCG) has significant advantages and can be categorized as a clean coal technology for producing syngas in situ. However, a comprehensive understanding of the process is lacking, because it takes place deep underground and consists of multiple phenomena. Hence UCG modelling can be employed to investigate different aspects of this process. While small-scale processes can be mechanistically informative, large-scale processes may behave quite differently. In this work, detailed 3D simulation modelling of three widely-applied UCG technologies was conducted for the Ardley coal formation (Alberta, Canada) in order to compare the performance of different technologies at field scale. The results of these comparisons can be helpful for selecting the right technology for a desired UCG pilot test. The results show that in spite of a higher heating value of produced syngas from the P-CRIP (parallel controlled retracting injection point) method over the L-CRIP (linear controlled retracting injection point) method, the volumetric rate and sweep efficiency of these methods are comparable. Moreover, we conducted 2D cross-sectional modelling of the Thulin test as the earliest UCG process at great depth and in tight coal seams to address modelling issues. Several possible approaches, such as geomechanical modelling, are presented to resolve the issues of UCG modelling in tight coal seams. The modelling results are analyzed and compared with the field results. Comparisons show an engineering match for the composition of the produced syngas. Computer Modelling Group's STARS software was used in this study as the porous medium modelling approach.