Heavy Oil Mobilization from Underground Coal Gasification in a Contiguous Coal Seam

Liangliang Jiang


This presentation shows that it is feasible to use UCG to mobilize overlying heavy oil with a creative deployment of wells in favor of an expanding thermal cavity. Oil well became the sole producer extracting both syngas and oil afterwards. UCG is able to drive thermal cavity into oil formation, and thus reduces significantly heavy oil viscosity in a short time. Oil temperature can be raised to over 300℃, manifesting UCG’s potential in extracting heavy oil of a ultra high viscosity; Contribution of UCG on heavy oil production is revealed to be a constant ramp-up, leading to an ultimate oil increment of seventeen fold in the modeling. Gravity drainage played a role in heavy oil mobilization. Thermal cavity expansion is overwhelmingly controlled by UCG itself, regardless of the use of oil wells or the presence of solution gas. However, the productivity of oil producers is better seen at a later stage when substantial oil is mobilized. Though a thicker coal delays heat transfer in the beginning, the benefits of more coal to bring excessive heat is expected to showcase when thermal cavity grows. Concerning the impact on viscosity, thermal effect really outperforms solution gas release.