天然气成因类型及判别标志

Genetic Indicators for Natural Gases

本文通过前人对天然气类型划分的分析，基于多年的研究结果，以“多源复合、多阶连续”的天然气成因新模式，提出了科学的天然成因类型划分方案，并讨论了不同成因类型天然气的地球化学特征。

Systematic classification for natural gases is not only a foundation for development of natural gas geological theory, but also very siginificant in exploration of natural gases. Based on a great deal of geological and geochemical data obtained from many years of academic research of our group and others, a new classification for natural gases was put forward under the guidence of 'multi-source complex and multi-stage continuity'. In this classification, natural gases were classified into the biogenic and abiogenic substantially,the biogenic natural gas was further divided into oil type gas and coal type gas according to its source organic matter.Natural gases were also classified dynamically as microbial gas, biothermo-catalytic transitional gas, thermo-catalytic decompositional gas, and high temperature decomposition gas. Different types of natural gases often show different geochemical behavoirs for the reason of variation in organic input, source rocks and thermal maturity. These geochemical properties provide indicators for classification of natural gases. The indicators include chemical compositional related ones: CH4 Index,C1 /C1-5, C2+, C2/C3,and Hg abundance; isotopic compositional ones: δ13C1, δ13C2,δ13C3,δ13C4, δ13Cco2,δDCH4, 3He/4He, 40 Ar/36 Ar; the companying liquid hydrocarbon indices:paraffin index,heptane index, alkane/aromatics index; and their internal relations.