天然气组分碳同位素倒转成因分析及地质应用

Genesis Analysis and Geological Application of Gas Component Carbon Isotope Reversal

为促进稳定碳同位素倒转现象在天然气地质勘探中的应用,通过调研大量国内外相关文献,系统地梳理和归纳了天然气烷烃组分稳定碳同位素序列倒转的成因及原理,包括有机成因气与无机成因气混合、细菌氧化降解作用、不同类型天然气(油型气和煤成气)混合、不同源或不同期天然气(如原生气与次生气)混合、高温及高压作用(气层气和水层气混合、硫酸盐热氧化还原反应、瑞利分馏作用)以及天然气运移扩散效应等。分析认为,碳同位素倒转现象在天然气地质勘探中具有广阔的应用前景,包括判识天然气的成因及来源,研究母质成熟度及天然气次生变化,反映气藏的地质特征(如成藏期次和沉积环境),以及判断天然气远景区等。

In order to promote the application of carbon isotope reversal in the geological exploration of natural gas,detailed and comprehensive literature review is completed to systematically summarize the geneses and principles of natural gas alkane component carbon isotope reversal. The corresponding geneses and principles include mixture of organic gas and inorganic gas,bacterial oxidative degradation,mixture of gases with different types( oil-gas and coal-gas),mixture of asynchronous gases or gases with different sources( such as primary gas and secondary gas),high-temperature and high-pressure( mixture of gases from gas layer and water layer,sulfate thermal oxidation-reduction reaction,Rayleigh fractionation),natural gas migration and diffusion,etc. Analysis shows that carbon isotope reversal can be widely applied in the geological exploration of natural gas. The corresponding major applications of carbon isotope reversal consist of identifying the genesis and source of natural gas,determining parent material maturity and secondary changes,characterizing natural gas geology and optimize the prospective area of natural gas.