Evolution of light hydrocarbon gases in subsurface processes: Constraints from chemical equilibrium

摘要: Abstract The behaviour of CH 4 , C 2 H 6 and 3 8 in subsurface processes such as magma intrusion, volcanic gas discharge natural generation have been examined from the viewpoint chemical equilibrium. It seems that equilibrium among these three hydrocarbons is attainable at about 200°C. When a system high temperatures cooled, re-equilibration continued until low temperature reached. rate which achieved, however, steadily diminishes and, below 200°C, reaction between stops composition this time frozen in, it remains unchanged metastable state for long period geological time. Natural compositions various fields shown that, when hydrocarbon out heated, gradually approaches above 150°C. On way towards equilibration, thermogenic gases apparently temporarily show thermodynamic constant higher than real expected ambient samples; contrast, biogenic indicate lower temperature. In regions, kinetic effects probably control composition; are essentially subjected to genetic operating on (such pyrolysis organic material bacterial activity) they fluctuate substantially. Examination experimental data, suggested equilibration sluggish comparison with reactive inorganic species S SO . view presented study will be helpful understanding create oil migration interpreting origins magmatic gases.