Natural gas is an important fuel that is likely to become increasingly important in the future. The deepest parts of many sedimentary basins are unexplored and remain frontier areas for natural gas exploration. Fundamental questions on the depth limits (if any) for natural gas survival and the processes operating to produce inorganic components (such as carbon dioxide, nitrogen, and hydrogen sulfide) remain unanswered. The composition of ultradeep gas can be calculated thermodynamically, and actual samples can be obtained from fluid inclusions that sampled gases present in the deep growth environment. Both methods were used in this study.