| Hydrogen sulfide concentration increases with depth in gas reservoirs with anhydrite, indicating that it, too, is a product of higher maturity.<ref name=ch11r20 />). The methane is reacting with the sulfate to form hydrogen sulfide and carbon dioxide gas. The reaction is probably kinetically controlled. | | Hydrogen sulfide concentration increases with depth in gas reservoirs with anhydrite, indicating that it, too, is a product of higher maturity.<ref name=ch11r20 />). The methane is reacting with the sulfate to form hydrogen sulfide and carbon dioxide gas. The reaction is probably kinetically controlled. |
− | The origin of nitrogen gas is not well characterized. In nonpetroleum basins, nitrogen may have high concentration because no other gas is present to dilute it. High-nitrogen gas in thermally mature basins is possibly from coal sources (<ref name=ch11r33>Stahl, W., Boigk, H., Wollanke, G., 1978, Carbon and nitrogen isotope data of upper Carboniferous and Rotliegend natural gases from north Germany and their relationship to the maturity of the organic source material: Advances in Organic Geochemistry 1976, p. 539–559.</ref> or from the mantle or deep crust<ref name=ch11r17>Jenden, P., D., Kaplan, I., R., 1989, Origin of natural gas in Sacramento basin, California: AAPG Bulletin, vol. 73, p. 431–453.</ref> | + | The origin of nitrogen gas is not well characterized. In nonpetroleum basins, nitrogen may have high concentration because no other gas is present to dilute it. High-nitrogen gas in thermally mature basins is possibly from coal sources (<ref name=ch11r33>Stahl, W., Boigk, H., Wollanke, G., 1978, Carbon and nitrogen isotope data of upper Carboniferous and Rotliegend natural gases from north Germany and their relationship to the maturity of the organic source material: Advances in Organic Geochemistry 1976, p. 539–559.</ref> or from the mantle or deep crust<ref name=ch11r17>Jenden, P., D., Kaplan, I., R., 1989, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0004/0400/0431.htm Origin of natural gas in Sacramento basin, California]: AAPG Bulletin, vol. 73, p. 431–453.</ref> |