Abstract:

The asphalt is ubiquity in the superimposed basins, NW of China, but now there are no quantitative evaluation methods of gas generated from asphalt. In response to this scientific issue, according to the mechanism of gas generated from asphalt, the method of chemical kinetics, which is successfully used for quantitative appraisement the oil-gas generated from kerogen and gas from oil cracking, is firstly applied to quantitatively evaluate the gas generation quantity from asphalt. Chemical kinetic model of gas generated from asphalt and from group compositions of chloroform bitumen “A” are established, and then kinetic models are extrapolated to the Silurian asphalt sand of Tazhong area, Tarim basin, combined with the thermal history of research area. The results indicate that, the process of gas generated from non-hydrocarbon is relatively earlier in the research area, and its transformation ratio increases significantly around a 3 500 m depth; the secondary process is the gas generated from asphaltene; and the latest is the gas generated from saturated hydrocarbon, which transformation ratio increased significantly around 4 200 m depth. Gas generation amount from Silurian asphaltic sands of Tazhong area is calculated using this established method.The result indicates that, the total amount of gas generated from saturated hydrocarbon, aromatic hydrocarbon, non-hydrocarbon and asphalteneis 8 160.68×10⁸m³, 6 573.21×10⁸m³, 9 719.3×10⁸m³ and 5 926.82×10⁸m³，respectively. The cumulative gas generation total amount reachs 30 377.97×10⁸m³.

Key words: asphalt, gas generation quantity, chemical kinetics, Tarim basin, Silurian