煤系天然气与煤层瓦斯甲烷碳同位素的差异及影响因素的初步探讨

PRELIMINARY COMMENT ON THE VARIATION OF CARBON ISOTOPIC COMPOSITION OF METHANE IN COAL MEASURE GAS AND SEAM GAS, AND ITS CONTROLLING FACTOR

戚厚发

Qi Houfa

石油工业部, 石油勘探开发科学研究院

Scientific Research Institute of Petroleum Exploration and Development, Ministry of Petroleum Industry

一般认为,天然气中甲烷碳同位素组成的差异,其主要影响因素是生气母质的类型和演化程度。即在相同成熟度的条件下,腐殖型母质生成天然气的碳同位素组成相对的比腐泥型母质生成的天然气为重。其δC13值,前者一般为-20— -30‰,后者为-30— -50‰。但是,在实际工作中发现,同一成熟度的煤系气藏的天然气与煤层瓦斯,在化学组份和碳同位素组成上有明显的差别。本文试图通过实际资料的分析,对其差异因素及其在天然气普查勘探中的实际意义做一些初步探讨。

The genetic types of natural gases are discussed according to the stable carbon isotopic composition of natural gases.It is found that the coal measure gas and the seam gas with the same maturity show great differences both in chemical and carbon isotopic composition.After various cor-relative analyses were made,the author proposes that the controlling factors of the differences are mainly,(1) the influence of biogenic methane in coalbed;and (2) the exchange of carbon isotopes between CH4 and CO2.

https://doi.org/10.11781/sysydz198502081