Coalbed gas: A review of research directions from the past to the future as facilitated by bibliometrics

This bibliometric review used coalbed gas articles published in the International Journal of Coal Geology (IJCG) from 1986 to 2022 catalogued in the Scopus database to compare similar articles indexed in the Web of Science (WoS) database from 1999 to 2016. Comparison focused between highly cited articles (top 1 % versus >100 citations in the WoS and Scopus databases, respectively) from the 2007–2016 period. Analysis of articles in the WoS database reveals research fronts center on modeling fractal pores related to gas adsorption and gas exploration in China's basins (Luo et al., 2017). In contrast, this study of research fronts of articles in the Scopus-IJCG database range from laboratory methods and models of coal reservoir properties; enhanced coalbed methane recovery and carbon dioxide storage; to experiments on microbes, methanogenesis, isotope geochemistry, and biochemical nutrients for biogenic gas generation. Thus, a key difference in coalbed-gas research fronts between the databases is disciplinary breadth for Scopus and discipline specific for WoS.

Caveats in interpreting analysis of citation numbers about research fronts include high rate of self-citation (“clubbing/inwardness”); researchers maintaining “continuous stream of publications for long periods”; growth of highly cited research of narrow fields with large datasets used to publish for prolonged periods; mass publications (“salami slicing”) to increase citation counts; researchers publishing in high-profile journals indexed by WoS for professional advancement; and experimental methods and review papers more cited than original papers. Also, the fall of gas prices from 2008 to 2014 facilitated rapid decrease in coalbed gas production and caused significant drop in the number of articles published in the IJCG from the United States and Europe. Conversely, the number of coalbed-gas articles from 2008 to 2022 increased 7–52 % for China and 25–33 % for Australia. Finally, analysis of IJCG articles reveals international research collaboration (IRC) grew up to 70 % by 2011 and became more diversified in research topics by 2022. Thus, IRC is the future pathway that brings together researchers to advance new knowledge of coalbed gas such as deep coalbed gas reservoirs to support Just Energy Transition as countries changeover to energy mix that moves away from coal to attain net-zero carbon emissions by 2050.