川东石炭系天然气成因类型和气源探讨

A DISCUSSION OF THE ORIGIN AND SOURCE OF THE NATURAL GAS IN CARBONIFEROUS,EASTERN SICHUAN BASIN

通过对川东石炭系气藏中天然气碳同位素特征的分析，指出δ^13C1>δ^13C2的反常特征是不同成熟度天然混合的结果。在同位素特征分析的基础上，进一步结合地质、地化资料，对川东石炭系天然气的成因类型和气源进行了探讨。认为川东石炭系天然气主要为油型裂解气，主力气源（县）应为以不整合与石炭系直接接触的下伏志留系，同时气中亦混有少量来自上覆下二叠统的成熟度略低的天然气。

On the basis of the analysis of carbon isotope characteristics and the components of the natural gas in the Carboniferous, eastern Sichuan Basin. It is shown that an anomalous phenomenon with δ13C1>δ13C2 is observed, which is related to the mixing of natural gas from various sources during their evolution. Based on the analysis of isotope characteristics and for the discussion of gas source, its type and formation, the gas from Silurian formation is considered as petroliferous gas and could be mixed with gas migrated from lower Permian. The gas in Carboniferous is considered as a mixture of petroliferous gas with different maturity from overlain source beds.