Assessment of Combustion Cavern Geometry in Underground Coal Gasification Process with the Use of Borehole Ground-Penetrating Radar

first_page settings Order Article Reprints Open AccessArticle Assessment of Combustion Cavern Geometry in Underground Coal Gasification Process with the Use of Borehole Ground-Penetrating Radar by Zenon Pilecki 1,* [ORCID] , Robert Hildebrandt 2 [ORCID] , Krzysztof Krawiec 1 [ORCID] , Elżbieta Pilecka 3 [ORCID] , Zbigniew Lubosik 2 [ORCID] and Tomasz Łątka 4 1 Mineral and Economy Research Institute of the Polish Academy of Sciences, Wybickiego 7A, 31-261 Cracow, Poland 2 Central Mining Institute, Plac Gwarków 1, 40-166 Katowice, Poland 3 Faculty of Civil Engineering, Cracow University of Technology, Warszawska 24, 31-155 Cracow, Poland 4 Faculty of Geology, University of Warsaw, Krakowskie Przedmieście 26/28, 00-927 Warsaw, Poland * Author to whom correspondence should be addressed. Energies 2023, 16(18), 6734; https://doi.org/10.3390/en16186734 Received: 19 August 2023 / Revised: 13 September 2023 / Accepted: 19 September 2023 / Published: 21 September 2023 (This article belongs to the Topic Energy Extraction and Processing Science) Download keyboard_arrow_down Browse Figures Versions Notes Abstract In this study, the shape and size of a combustion cavity with a fracture zone in the gasified coal seam was determined with the use of control boreholes and a ground-penetrating radar (BGPR) test. The underground coal gasification (UCG) field-scale experiment was performed in Carboniferous strata in coal seam 501 at a depth of approx. 460 m in the Wieczorek hard coal mine in the Upper Silesian Coal Basin, Poland. After the termination of the UCG reactor, five coring boreholes were drilled to identify the geometry of the resulting combustion cavity and the impact of the UCG process on the surrounding rock mass. Borehole ground-penetrating radar measurements were performed using a 100 MHz antenna in three boreholes with a length of about 40–50 m. This enabled the identification of the boundaries of the combustion cavity and the fracture zone in the coal seam. The fracture zones of rock layers and lithological borders near the control borehole were also depicted. As a result, the cavity was estimated to have a length of around 32 m, a width of around 7 m and a height of around 5 m. The analyses performed with the control boreholes and the BGPR provided sufficient information to determine the geometry of the combustion cavity and the fracture zone.