UCG engineering demonstrations in Australia: History and its implications

Underground coal gasification (UCG), which is a revolutionary coal mining technology, is an important direction for achieving a low-carbon and efficient coal energy structure in China and is also a potential explorable way to ensure the smooth realization of the peak carbon dioxide emissions and carbon neutrality in China. Based on a literature survey, this study sorts out the exploration process of UCG technologies in Australia and analyzes the gains and losses using field test cases. The experience in UCG technologies in Australia can provide a reference for the development of the technologies in China. The results show that the exploration of UCG technologies in Australia can date from the 1970s, followed by UCG field experiments for up to 15 years. As a result, three UCG demonstration projects have been launched in sequence, including the largest, successfully implemented on-site demonstration project outside the former Soviet Union to date. Despite several twists and turns, significant progress has been made, and relevant achievements act as models of global UCG industrialization. The exploration and development of UCG (research and development) technologies in Australia demonstrate that it is feasible to introduce nongovernmental capital to support the costly R&D and field tests of UCG technologies. Moreover, the risks of UCG field tests can be reduced by fully investigating and referencing global experience. According to the experience, an important development direction of the UCG industry is to produce diversified final products using syngas. Regarding engineering technologies, the drilling design and engineering quality are the key to the reliable operation of a UCG gasifier. In particular, materials for well cementing should be determined given the heating-induced shrinkage and expansion of borehole walls. Moreover, the pure oxygen injection device should be equipped with an automatic tripping system to ensure safe UCG production, the sealing performance of a gasifier and its pipelines should be strictly guaranteed in each link of the entire UCG engineering, and it is necessary to conduct geological evaluation and siting in the early stage. Furthermore, various factors should be comprehensively taken into account in the UCG design to ensure the optimal configuration of gasifier-associated wells in the gasification area based on the single-gasifier rolling production. Meanwhile, the development of systematic and detailed industrial policies is the basic guarantee to promote UCG industrialization, and the degree of the prior communication between enterprises and government departments in charge tends to determine the success or failure of UCG projects.