331 were confirmed in other sections. Figure 3 shows the borehole water remaining in Well-1 and Well-2. The figure indicates that borehole water, which had not been discharged after drilling, was observed at approximately 19 m depth in both wells. In Well-3, it was confirmed that the upper sandstone layer consists of intact rock with few fractures. Table 1 lists the results of proximate and ultimate analysis of coal samples collected from the drilling cores of the co-axial well. The calorific value is 17.98 MJ/kg (4,300 kcal/kg), and the carbon content is relatively low at 45.8%. This is attributed to the high ash content of 38.2%, reflecting the frequent presence of interbeds within the coal seam. Figure 1 – Arrangement diagram of the field UCG trial Figure 2 – Drilling core samples obtained from the 5 m section at the co-axial well bottom
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