Soviet experience of underground coal gasification focusing on surface subsidence

Global coal mining activity is increasing due to demands for cheap energy and the availability of large coal deposits around the world; however, the risks associated with conventional coal mining activities remain relatively high. Underground coal gasification (UCG), also known as in-situ coal gasification (ISCG) is a promising alternative method of accessing energy resources derived from coal. UCG is a physical-chemical-geotechnical method of coal mining that has several advantages over traditional mining, for example, its applicability in areas where conventional mining methods are not suitable and the reduction of hazards associated with working underground. The main disadvantages of UCG are the possibility of underground water pollution and surface subsidence. This work is focused on the latter issue. A thorough understanding of subsidence issues is a crucial step to implement UCG on a wide scale. Scientists point out the scarce available data on strata deformations resulting from UCG. The former Soviet Union countries have a long history of developing the science related to UCG and experimenting with its application. However, the Soviet development occurred in relative isolation and this makes a modern review of the Soviet experience valuable. There are some literature sources dealing with Soviet UCG projects; however, they are neither up-to-date nor focus on aspects that are of particular importance to surface subsidence, including geological profiles, strata physical-mechanical properties, thermal properties of geomaterials, and temperature spreading. The goal of this work is to increase the knowledge on these aspects in the English-speaking science community.