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已有一些模型把~(13)CH_4和~(12)CH_4的生成当作初期裂解的一系列平行初级反应来计算天然气(甲烷)稳定碳同位素组成的变化。本项研究的目的是把同位素分馏的类型和已建立的天然气生成的动力学模型结合起来。沉积有机物形成的甲烷稳定碳同位素比值取决于有机质中甲烷母质的初始碳同位素比值和来自相应母质中~(12)C和~(13)C甲烷之间活化能的内在差异。在开放体系的裂解实验中,新模型对于δ~(13)C观察值的变化能给予理论解释和数学描述,能模拟出任何地温下热成因气中甲烷的碳同位素值。对西伯利亚西北部的Pokur组中的2个含煤岩样进行模拟实验,得到了与Pokur组气藏天然气接近的甲烷碳同位素值(δ~(13)C_1=-42‰～-54‰)。这一发现支持了在成熟阶段早期的天然气热解成因。
Some models have been used to calculate the change of the stable carbon isotope composition of natural gas (methane) using the generation of ~ (13) CH_4 and ~ (12) CH_4 as a series of parallel primary reactions of initial cracking. The purpose of this study was to combine the type of isotopic fractionation with established kinetic models for the generation of natural gas. The stable carbon isotope ratio of methane formed by the deposition of organic matter depends on the initial carbon isotope ratio of the methane parent in the organic matter and the intrinsic difference in activation energy between ~ (12) C and ~ (13) C methane from the corresponding parent material. In the open system cracking experiment, the new model can give a theoretical explanation and mathematical description of the change of δ ~ (13) C observations and simulate the carbon isotope values of methane in the thermogenic gas at any geothermal temperature. The simulations of two coal-bearing rocks in the Pokur Formation in the northwestern Siberia show that the carbon isotope values (δ ~ (13) C_1 = -42 ‰ ~ -54 ‰) close to the natural gas in the Pokur Formation are obtained. This finding supports the genesis of natural gas pyrolysis early in the maturity phase.