As gas production from conventional gas reservoirs in the United States decreases, industry is turning more attention to the exploration and development of unconventional gas resources (UGR). This trend is expanding quickly worldwide. Unlike North America where development of UGRs and technology is now mature and routine, many countries are just beginning to develop unconventional gas resources. Rogner (1996) estimated that the unconventional gas in place, including coalbed methane, shale gas and tight-sand gas, exceeds 30,000 Tcf worldwide. As part of a research team, I helped to develop a software package called Unconventional Gas Resource Advisory (UGRA) System which includes the Formation Analog Selection Tool (FAST) and Basin Analog Investigations (BASIN) to objectively and rapidly identify and rank mature North American formations and basins that may be analogous to nascent international target basins. Based on BASIN and FAST results, the relationship between mature and underexplored basins is easily accessed. To quantify the unconventional resource potential in typical gas basins, I revised and used a computer model called the Petroleum Resources Investigation Summary and Evaluation (PRISE) (Old, 2008). This research is based on the resource triangle concept, which implies that all natural resources, including oil and gas, are distributed log-normally. In this work, I describe a methodology to estimate values of technically recoverable resources (TRR) for unconventional gas reservoirs by combining estimates of production, reserves, reserves growth, and undiscovered resources from a variety of sources into a logical distribution. I have also investigated mature North American unconventional gas resources, and predict unconventional resources in underexplored basins worldwide for case study. Based on the results of testing BASIN and PRISE, we conclude that our evaluation of 24 North American basins supports the premise that basins analysis can be used to estimate UGRs.