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Abstract
In this experiment the scheme of linked vertical wells for in-situ coal gasification was used with an 18.3-m well spacing. The experiment took 100 days for air-flow testing, reverse-combustion linking, forward-combustion gasification, and postburn steam flow. Air was used for gasification except for a 2-day test with oxygen and steam flow. Reverse-combustion linking took 14 days at 1.6 m/day and used 0.40 Mgmol of air per meter of link. At least two linkage paths were formed. The detected links stayed below the 3 m level in the 7.6 m coal seam; however, the product flow from the forward-burn gasification probably followed the coal-overburden interface, rather than the reverse-burn links at the 3-m level. Forward-burn gasification took 58 days and produced a total of 232 Mgmol (194 Mscf) of gas with an average heating value of 96 kJ/gmol (108 Btu/scf(. During the oxygen-steam test, the heating value averaged 235 kJ/gmol (265 Btu/scf). The coal recovery was 1310 m3 (1950 ton). Gasification was terminated because of decreasing product quality, not because the burn had reached the production well. Product quality decreased as a result of increasing heat loss to inert materials underground.