The origin of natural gas and the hydrocarbon charging history of the Yulin gas field in the Ordos Basin, China
The origin of natural gas and the hydrocarbon charging history of the Yulin gas field in the Ordos Basin, China
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DOI：
10.1016/j.coal.2009.07.016
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发表时间：
2010-04-01
影响因子：
5.6
通讯作者：
Han Zhongxi
中科院分区：
文献类型：
--
作者：
Hu Guoyi;Li Jin;Han Zhongxi
结合天然气碳同位素组成、轻烃地球化学特征、碳同位素分馏模型结果和流体包裹体分析，研究了鄂尔多斯盆地榆林气田天然气的成因类型、来源和充注史。榆林气田甲烷和乙烷的碳同位素组成相对富集C-13，δ C-13（1）值为35.3 ~-29.8 ‰（平均值= 32.4份/千）和δ C-13（2）范围为26.3份/千至-23.5份/千（平均值= -24.8份/千）。C-7轻烃以甲基环己烷为主，占65.8%~ 80.9%（平均值为71.6%），具有煤成气的特征。此外，天然气地球化学研究表明，尽管该区存在海相灰岩烃源岩，但该烃源岩的油伴生气对榆林气田的贡献很小。根据气源岩δ C-13（1）与Ro的经验关系，以及榆林气田天然气动力学同位素分馏预测，发现甲烷的δ C-13比仅来源于原地煤系的天然气的δ C-13重。这一结果表明，榆林气田的天然气不仅来自于当地煤系烃源岩生成的天然气，而且来自于气田南部或西南部煤系烃源岩生成的成熟度较高的天然气。流体包裹体分析证明，榆林气田天然气成藏具有连续充注的特征。(C)2009 Elsevier B. V.保留所有权利。
The genetic type, source and charging history of natural gas in the Yulin gas field in the Ordos Basin have been studied by combining the carbon isotopic composition of natural gas and geochemical characteristics of light hydrocarbons with carbon isotope fractionation model results and fluid inclusion analysis. The carbon isotopic composition of methane and ethane in the Yulin gas field is relatively enriched in C-13 with delta C-13(1) values ranging from 35.3 parts per thousand to -29.8 parts per thousand (average value = 32.4 parts per thousand) and delta C-13(2) ranging from 26.3 parts per thousand to -23.5 parts per thousand (average value = -24.8 parts per thousand). The C-7 light hydrocarbons are predominated by methylcyclohexane, accounting for 65.8% to 80.9% (average value = 71.6%), which is characteristic of coal-derived gas. Furthermore, the gas geochemistry indicates that, although marine limestone source rocks are present in the region, the contribution of oil-associated gas from this source to the Yulin gas field is quite low. Based on the empirical relationship between delta C-13(1) and %Ro of gas source rocks, and the kinetic isotope fractionation predictions for gases generated in the Yulin gas field, the observed delta C-13 of methane is heavier than that of natural gas only originated from in-situ coal-measures. This result shows that gas in the Yulin gas field is contributed not only by the natural gas generated from local coal-measure source rocks, but also from the higher maturity natural gas sourced from the coal-measure source rocks to the south or southwest of this gas field. Fluid inclusion analysis proves that the accumulation of natural gas in the Yulin gas field has the characteristics of continuous charge. (C) 2009 Elsevier B.V. All rights reserved.