鄂尔多斯盆地杭锦旗地区天然气地球化学特征及气源探讨

Geochemical characteristics and sources of natural gas in Hangjinqi area of Ordos Basin

张迈 宋到福 王铁冠 何发岐 张威 安川 刘悦 陆振港

ZHANG Mai SONG Daofu WANG Tieguan HE Faqi ZHANG Wei AN Chuan LIU Yue LU Zhengang

1. 中国石油大学(北京) 油气资源与工程全国重点实验室, 北京 102249; 2. 中国石化 华北油气分公司, 郑州 450000

1. National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China; 2. North China Company, SINOPEC, Zhengzhou, Henan 450000, China

为明确鄂尔多斯盆地杭锦旗地区不同区带天然气特征及来源上的差异，通过天然气气体组分分析和碳同位素分析等手段，对杭锦旗地区3个主要勘探区带天然气地球化学组成特征进行了详细的对比剖析，并结合各区带天然气在成藏过程中的差异，对其来源进行了分析探讨。研究区天然气烃类气体含量较高(以甲烷为主)，干燥系数多低于0.95，整体呈现出湿气特征，非烃类气体主要为二氧化碳和氮气，含量较低；天然气碳同位素δ13C1、δ13C2和δ13C3组成表现为正碳序列分布，但不同区带天然气碳同位素组成之间存在着差异，其中什股壕区带天然气δ13C1值最重，而新召区带天然气δ13C2和δ13C3值要明显重于其他2个区带。成因分析结果表明，研究区3个区带天然气均为有机成因气，呈现出煤型气(腐殖型气)的特征，主体为干酪根初次裂解气，且其气源岩处于高成熟—过成熟热演化阶段。结合气源对比结果与地质背景，推测新召区带天然气主要由下伏山西组烃源岩供烃，独贵加汗和什股壕区带天然气则来源于断裂南部太原组和山西组烃源岩的共同贡献，但前者太原组烃源岩贡献比例相对更高。

In order to clarify the differences of characteristics and sources of natural gas in different zones in Hangjinqi area of Ordos Basin, the geochemical composition characteristics of natural gas in three major exploration zones in Hangjinqi area were compared and analyzed in detail by means of gas composition analysis and carbon isotope analysis, and sources of natural gas in different zones were discussed based on the differences in the process of gas accumulation in different zones. The results show that the natural gas of the study area has a high content of hydrocarbon gases (mainly methane), and the drying coefficients are mostly lower than 0.95, suggest-ing that the natural gas is dominated by wet gases. The non-hydrocarbon gases are mainly carbon dioxide and nitrogen, which have lower contents. The carbon isotopes δ13C1, δ13C2 and δ13C3 of natural gas show a positive carbon series distribution, but there are differences among natural gas carbon isotopes compositions in different zones. The δ13C1 value of natural gas in Shiguhao zone is the heaviest, and the δ13C2 and δ13C3 values of natural gas in Xinzhao zone are significantly heavier than that in the other two zones. The genetic analysis results show that the natural gas in the three regions of the study area is of organic genesis, showing the characteristics of coal-type gas (humus-type gas), and the main body is kerogen primary cracking gas, and the source rocks are in the stage of high-mature to over-mature thermal evolution. Combined with the results of gas-source correlation and geological background, it is inferred that the natural gas in Xinzhao zone is mainly derived from the underlying source rocks of Shanxi Formation, and the natural gas in Duguijiahan and Shiguhao zones is sourced from the source rocks of Taiyuan and Shanxi formations in the southern part of the fault, but Taiyuan source rocks contribute more.

国家重点研发计划项目“富氦天然气成藏机制及氦资源分布预测技术”(2021YFA0719000)资助。

https://doi.org/10.11781/sysydz202401124