ABSTRACT

Organic-inorganic reactions during thermochemical sulfate reduction (TSR) are the main cause for the destruction of hydrocarbons in deep carbonate sediments. In this paper, thermal simulation experiments on C₁—C₃ hydrocarbons and solid calcium sulfate were carried out using an autoclave operated at high temperature and high pressure. The gas and solid products were characterized by advanced analytical methods including microcoulometry, gas chromatography and FT-IR. The kinetics and thermodynamics were investigated on the basis of the experimental data, and the results showed that the reactions of C₁—C₃ hydrocarbons and solid calcium sulfate can proceed spontaneously in the laboratory to produce H₂S, H₂O, and CaCO₃ as the main products. From the kinetic calculation, it is found that these three reactions are zero order reactions with activation energies of 152.9 kJ/mol, 131.0 kJ/mol and 120.6 kJ/mol, respectively. When extrapolated to geological temperatures, the time needed to reach 50% conversion at the temperature of 200°C for the reaction between CH₄ and CaSO₄ is 1.44 million years.