Large scale simulation of UCG process applying porous medium approach

Abstract

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 crosssectional 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.

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Outlook for the coal industry and new coal production technologies

“…Chemical reactions convert the coal to syngas by pyrolysis, combustion and gasification reactions in a manner similar to those processes in a surface gasifier. The produced syngas is a mixture of mainly carbon monoxide and hydrogen, which can be used as fuel for power generation and feedstock for various chemical products (i.e., hydrogen and ammonia) (Nourozieh et al, 2010;Seifi et al, 2015). The carbon captured during syngas utilization can be used for enhanced oil recovery.…”

Effect of Fixed and Removable Gas-Injection Patterns on the Expansion of Reaction Zones during Underground Coal Gasification

“…23 Seifi et al simulated the CRIP process based on chemical kinetics and transfer of heat and mass, which was useful to pilot experiments. 24,25 During the UCG process using fixed and removable gas-injection points, a cavity will form in the reaction zone, and the chemical reaction on the surface of the cavity depends on the reaction temperature, gas diffusion velocity, and effective area of the reaction zone. 26,27 Perkins studied the effects of technological parameters on the expansion of the cavity, including pressure, composition of gasification agents, coal quality, and coal-seam thickness.…”

“…The syngas produced was used to generate hydrogen, and an industrial test was then carried out in the Wieczorek (Poland) mine in a following study, proving that UCG technology was safe and effective . Seifi et al simulated the CRIP process based on chemical kinetics and transfer of heat and mass, which was useful to pilot experiments. , During the UCG process using fixed and removable gas-injection points, a cavity will form in the reaction zone, and the chemical reaction on the surface of the cavity depends on the reaction temperature, gas diffusion velocity, and effective area of the reaction zone. , Perkins studied the effects of technological parameters on the expansion of the cavity, including pressure, composition of gasification agents, coal quality, and coal-seam thickness . However, until now, few studies have covered the effects of different gas-injection methods on the expansion of the three zones (oxidation, reduction, and dry distillation) in the UCG process.…”