Changes

Carbon dioxide, hydrogen sulfide, and nitrogen can constitute a significant percentage of natural gas from some [[accumulation]]s. In some cases, natural gas is uneconomic due to the high nonhydrocarbon gas content.

Carbon dioxide, hydrogen sulfide, and nitrogen can constitute a significant percentage of natural gas from some [[accumulation]]s. In some cases, natural gas is uneconomic due to the high nonhydrocarbon gas content.

Although low concentrations of carbon dioxide can be derived from organic sources or byproducts of silicate reactions at moderate temperatures<ref name=ch11r32>Smith, J., T., Ehrenberg, S., N., 1989, Correlation of carbon dioxide abundance with temperature in clastic hydrocarbon reservoirs: relationship to inorganic chemical equilibrium: Marine and Petroleum Geology, vol. 6, p. 129–135., 10., 1016/0264-8172(89)90016-0</ref> high concentrations of carbon dioxide are usually associated with igneous intrusion or regional heating of impure limestones.<ref name=ch11r9>Farmer, R., E., 1965, [http://archives.datapages.com/data/specpubs/methodo2/data/a071/a071/0001/0350/0378.htm Genesis of subsurface carbon dioxide], in Young, A., Galley, J., eds., Fluids in Subsurface Environments: AAPG Memoir No. 4, p. 378–385.</ref>

Although low concentrations of carbon dioxide can be derived from organic sources or byproducts of silicate reactions at moderate temperatures<ref name=ch11r32>Smith, J. T., and S. N. Ehrenberg, 1989, Correlation of carbon dioxide abundance with temperature in clastic hydrocarbon reservoirs: relationship to inorganic chemical equilibrium: Marine and Petroleum Geology, vol. 6, p. 129–135., 10., 1016/0264-8172(89)90016-0</ref> high concentrations of carbon dioxide are usually associated with igneous intrusion or regional heating of impure limestones.<ref name=ch11r9>Farmer, R. E., 1965, [http://archives.datapages.com/data/specpubs/methodo2/data/a071/a071/0001/0350/0378.htm Genesis of subsurface carbon dioxide], in A. Young, and J. Galley, eds., Fluids in Subsurface Environments: AAPG Memoir No. 4, p. 378–385.</ref>

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, [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>

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., H. Boigk, and G. Wollanke, 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.,and I. R. Kaplan, 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>

==Predicting burial destruction==

==Predicting burial destruction==