首页|天然气运移轻烃地球化学示踪——以鄂尔多斯盆地东胜气田为例

天然气运移轻烃地球化学示踪——以鄂尔多斯盆地东胜气田为例

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基于天然气中轻烃化合物组成分析和区域性对比,结合组分和甲烷碳同位素组成特征,揭示轻烃地球化学特征对鄂尔多斯盆地东胜气田上古生界天然气运移和水溶及逸散等示踪作用,探讨运移作用对特定轻烃指标的关联效应.研究表明:①东胜气田二叠系下石盒子组天然气C5-7异构烷烃含量高于正构烷烃,C6-7轻烃组成呈链烷烃优势分布且芳香烃含量明显偏低(小于4.0％),C7轻烃主体呈甲基环己烷优势分布,整体表现出煤成气特征且受到了水溶等作用影响;②东胜气田天然气经历了自南向北的游离相运移,并在充注后发生不同程度的水溶作用,其中泊尔江海子断裂以北什股壕地区天然气在聚集后具有明显的散失;③长距离的游离相运移导致天然气C7轻烃中甲基环己烷相对含量和甲苯/正庚烷值降低、正庚烷/甲基环己烷值和庚烷值增大,水溶作用导致轻烃异庚烷值增大,天然气散失导致什股壕地区天然气中C5-7正构烷烃相对异构烷烃含量增加.
Tracing of natural gas migration by light hydrocarbons:A case study of the Dongsheng gas field in the Ordos Basin,NW China
Based on the analysis of light hydrocarbon compositions of natural gas and regional comparison in combination with the chemical components and carbon isotopic compositions of methane,the indication of geochemical characteristics of light hydrocarbon on the migration features,dissolution and escape of natural gas from the Dongsheng gas field in the Ordos Basin is revealed,and the effect of migration on specific light hydrocarbon indexes is further discussed.The study indicates that,natural gas from the Lower Shihezi Formation(P1 x)in the Dongsheng gas field displays higher iso-C5-7 contents than n-C5-7 contents,and the C6-7 light hydrocarbons are composed of paraffins with extremely low aromatic contents(＜0.4％),whereas the C7 light hydrocarbons are dominated by methylcyclohexane,suggesting the characteristics of coal-derived gas with the influence by secondary alterations such as dissolution.The natural gas from the Dongsheng gas field has experienced free-phase migration from south to north and different degrees of dissolution after charging,and the gas in the Shiguhao area to the north of the Boijianghaizi fault has experienced apparent diffusion loss after accumulation.Long-distance migration in free phase results in the decrease of the relative contents of the methylcyclohexane in C7 light hydrocarbons and the toluene/n-heptane ratio,as well as the increase of the n-heptane/methylcyclohexane ratio and heptane values.The dissolution causes the increase of isoheptane values of the light hydrocarbons,whereas the diffusion loss of natural gas in the Shiguhao area results in the increase of n-C5-7 contents compared to the iso-C5-7 contents.

Ordos BasinDongsheng gas fieldPermian Lower Shihezi Formationlight hydrocarbon compoundsmaturitynatural gas originmigration phase statediffusion loss

吴小奇、倪春华、马亮帮、王付斌、贾会冲、王萍

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中国石化石油勘探开发研究院无锡石油地质研究所,江苏无锡 214126

中国石化油气成藏重点实验室,江苏无锡 214126

中国石化华北油气分公司油气勘探管理部,郑州 450006

中国石化华北油气分公司勘探开发研究院,郑州 450006

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鄂尔多斯盆地 东胜气田 二叠系下石盒子组 轻烃化合物 成熟度 天然气成因 运移相态 散失作用

国家自然科学基金国家自然科学基金中国石化科技攻关计划中国石化科技攻关计划

42172149U2244209P23230P22132

2024

10.11698/PED.20230640

石油勘探与开发
中国石油天然气股份有限公司勘探开发研究院 中国石油集团科学技术研究院

石油勘探与开发

CSTPCD北大核心
影响因子：4.977
ISSN：1000-0747
年,卷(期)：2024.51(2)
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