页岩气稳定碳同位素特征研究  

Characteristics of Stable Carbon Isotopic Composition of Shale Gas

作　　者：屈振亚 孙佳楠[1,2] 史健婷[1,2] 詹兆文[1,2] 邹艳荣[1] 彭平安[1] 

机构地区：[1]中国科学院广州地球化学研究所有机地球化学国家重点实验室,广东广州510640 [2]中国科学院大学,北京100049

出　　处：《天然气地球科学》2015年第7期1376-1384,共9页Natural Gas Geoscience

基　　金：国家自然科学基金(编号:41273059);中国科学院战略性先导科技专项(编号:XDB10010202)联合资助

摘　　要：选用低成熟富Ⅱ型有机质页岩,在真空MSSV体系中分别以2℃/h、20℃/h的升温速率进行生烃模拟实验,测定气态烃的稳定碳同位素组成并讨论了页岩干酪根热解气态烃演化的稳定碳同位素特征及页岩气碳同位素倒转的原因。热解气态烃中甲烷碳同位素组成随热模拟实验中温度升高先变轻后变重,乙烷和丙烷的碳同位素组成都是随着温度的升高逐渐变重。影响页岩气碳同位素组成的主要因素包括:有机质类型、热演化程度以及气体在页岩系统中的微运移。页岩气烷烃序列稳定碳同位素值出现倒转的原因目前尚不十分清楚,但根据热模拟实验结果可以得出单纯热成因的页岩气的碳同位素组成不会发生倒转,因此发生同位素倒转的页岩气必定有其他地球化学过程的介入。对Barnett、Fayetteville页岩气同位素数据分析表明,该页岩气形成过程很有可能发生了水煤气反应和费—托合成作用。Pyrolysis experiments were conducted with low maturity kerogen isolated from type ]1 organic-rich shale in a vacuum MSSV（Micro scale sealed vessel） system,to simulate gas hydrocarbon generation at two heating rates of 2℃/h,20℃/h. The stable carbon isotopic compositions of generated gas hydrocarbon were measured to investigate their characteristics and influencing factors. At the beginning,δ13C value of meth- ane becomes more negative with increasing temperature until reaching the lightest point, then it changes more positive and the δ13C value of ethane and propane shows a positive trend with elevated temperatures. The main factors impact on carbon isotope of shale gas may include： type of organic matter, maturity of the shale and micro-migration of gas in shale gas systems. Although it is still unclear the reason leading to car- bon isotope reversal,we can conclude that isotopic reversal phenomenon wouldn＇t happen in a single ther- mogenic gas reservoir according to our pyrolytic experiment results, thus it must be involved with some other geochemical processes. Carbon isotope compositions of gas from the Fayetteville and Barnett shales show that it may include water-gas reaction and Fisch, er-Tropsch synthesis during its formation.

关 键 词：页岩气 碳同位素 热解 干酪根 同位素倒转 

分 类 号：TE122.113[石油与天然气工程—油气勘探]