页岩气稳定碳同位素组成特征及应用前景

Characteristics of Stable Carbon Isotope of Shale Gas and Their Application Prospects

页岩气作为一种自生自储的非常规天然气,其稳定碳同位素组成可能具有与常规天然气不同的特征。综述了页岩气碳同位素特征和应用方面的最新研究,包括高成熟页岩中存在天然气的甲烷碳同位素组成(δ13C1)大于乙烷碳同位素组成(δ13C2)的"反序"现象及其成因;在页岩气生产或现场解吸过程中,δ13C1随时间增加而逐渐变重现象和页岩气稳定碳同位素参数在判别页岩气成因类型、预测页岩气的产能以及吸附气与游离气相对含量和判断页岩储集物性等方面的应用。认为进一步开展页岩气稳定碳同位素组成特征、碳同位素变化与吸附气和游离气相对含量的关系和开采或现场解吸过程中同位素变重程度与页岩储集物性的关系等方面的研究,建立起相应的预测模型,对有效指导页岩气勘探开发具有重要意义。

Shale gas is an unconventional gas with self-generation and self-preservation characteristics, which may cause different stable carbon isotope compositions from regular natural gas. We summarize the most updated research on the carbon isotope composition of shale gas, including genesis of the methane stable carbon isotope values （δ13 C1 ） within high maturity shale that are heavier than ethane stable carbon i- sotope values （δ13C2）. δ13C1 becomes heavier with the increase of desorption time or productivity time. In addition, four applications of the carbon isotopes are introduced： ① identifying the origins of shale gas; ② forecasting the productivity of shale gas; ③ quantifying the absorbed gas and free gas in shale gas; and ④ forecasting the physical prolaertv of shale.