四川盆地须家河组及侏罗系煤成气碳同位素组成  

Carbon isotopic compositions of coal-derived gas in the Xujiahe Formation and Jurassic in the Sichuan Basin

作　　者：吴小奇[1,2] 黄士鹏[1] 廖凤蓉 李振生[3] 

机构地区：[1]中国石油勘探开发研究院 [2]中国科学技术大学地球和空间科学学院 [3]合肥工业大学资源与环境工程学院

出　　处：《石油勘探与开发》2011年第4期418-427,共10页Petroleum Exploration and Development

基　　金：国家自然科学基金(4070202140972134);中国科学技术大学研究生创新基金项目(KD2007061)

摘　　要：四川盆地须家河组煤系烃源岩为须家河组自生自储气藏和上覆侏罗系次生气藏提供气源。须家河组气藏主要分布在川西和川中气区,侏罗系气藏主要分布在川西气区。须家河组煤系烃源岩生成的天然气为典型热成因气,表现出腐殖型气的特点。整体上看侏罗系天然气的碳同位素特征与须家河组天然气基本一致,须家河组煤成气碳同位素组成表现出自下而上逐渐变轻的趋势;侏罗系各层天然气则由于来源不尽相同而碳同位素组成规律性不明显,但具有近源聚集的特点。横向上川西气区南部烷烃气δ13C值大于北部,且均明显大于川中和川南气区的值。须家河组和侏罗系中少许气样发生了碳同位素的倒转,主要是受同源不同期气混合的影响。油型气的混合不仅使得川中气区部分煤成气气样δ13C值偏小,而且导致部分气样发生碳同位素的倒转。Coal-measure source rocks of Xujiahe Formation in the Sichuan Basin are important gas-source rocks,and provide sufficient natural gas for self-generation and self-storage gas reservoirs in the Xujiahe Formation and secondary gas reservoirs in the overlying Jurassic.The gas reservoirs in the Xujiahe Formation are mainly located in the western and central Sichuan gas provinces,while those in the Jurassic in the western Sichuan gas province.Natural gas derived from coal-measure source rocks in the Xujiahe Formation are typical thermogenic gas and shares the same characteristics of humic type gas.The carbon isotopic characteristics of gas samples in the Jurassic are generally identical to those in the Xujiahe Formation.The carbon isotopic compositions of the coal-derived gas tend to become lighter from bottom to top in the Xujiahe Formation.The gases in the Jurassic have no clear rule due to their coming from different members of the Xujiahe Formation,and they tend to accumulate near the source.Horizontally,the δ13C values of alkane gas from the southern part of the western Sichuan gas province are heavier than those from the northern part,while both are obviously greater than those in the central and southern Sichuan gas provinces.Several gas samples in the Xujiahe Formation and Jurassic are characterized by partially reversed carbon isotopic series,mainly due to the influence of mixing of gas from the same source but different periods.The mixing of oil-associated gas not only reduces the δ13C values of several coal-derived gas samples in the central Sichuan gas province,but also causes the partial reversal of carbon isotopic series of some gas samples.

关 键 词：四川盆地 须家河组 侏罗系 煤成气 碳同位素 

分 类 号：TE132.2[石油与天然气工程—油气勘探]