| 李璠洁,田亚铭,袁龙,夏文谦,何佳玲,施泽进.川北元坝地区中二叠统茅口组天然气成因及来源分析[J].贵州地质,2025,42(4):452-465 |
| 川北元坝地区中二叠统茅口组天然气成因及来源分析 |
| Analysis on Genesis and Source of Natural Gas in the Middle Permian Maokou Formation in Yuanba Area of Northern Sichuan Basin，China |
| 投稿时间：2025-07-23 |
| DOI： |
| 中文关键词: 天然气成因类型 生物标志化合物 气源分析 元坝地区 茅口组 |
| 英文关键词:Genetic type of natural gas Biomarker compounds Gas source analysis Yuanba area Maokou formation |
| 基金项目: |
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| 中文摘要: |
| 随着四川盆地的天然气勘探不断地深入，在元坝地区二叠系茅口组海相碳酸盐岩地层中取得了天然气勘探突破，但开发未达到理想效果，该地区天然气成因及来源不明确的问题是制约该区加强下步勘探的主要问题之一。为此，在充分利用野外及测试分析资料的基础上，总结元坝地区茅口组天然气地球化学特征，结合天然气成因判别图版对比相邻层系天然气，根据乙烷碳同位素进行气-源对比，以及对储层沥青及烃源岩的生物标志化合物特征进行分析，明确了元坝地区茅口组天然气成因类型及其主力源岩。研究结果表明:①元坝地区茅口组天然气中CH4含量最高(含量介于6760%9794%)，乙烷及丙烷含量均低于100%，不含有丁烷及以上烷烃气体，干燥系数(C1/C1-5)均大于099，是典型的高演化干气；天然气碳同位素较重，δ13C1均值为-2912‰，δ13C2均值为-2815‰。②茅口组天然气部分为高成熟煤型气，部分为高成熟-过成熟油型-煤型混合气，表现出不同成熟的II型干酪根裂解气与原油裂解气的混合气的特征。③茅口组天然气δ13C2与吴家坪组、茅口组烃源岩δ13Ckerogen特征一致，且茅口组储层沥青生物标志化合物与吴家坪组、茅口组烃源岩均具有相似性表明元坝地区中二叠统茅口组天然气为混源气，来源于吴家坪组及茅口组烃源岩。 |
| 英文摘要: |
| With the continuous deepening of natural gas exploration in Sichuan Basin，a breakthrough has been made in the Marine carbonate strata of Permian Maokou Formation in Yuanba area，but the development has not yet meet the expected targetsThe uncertainty of the natural gas genesis and source in this area is one of the main problems restricting further exploration in this areaTherefore，on the basis of making full use of field and test analysis data，we summarized the geochemical characteristics of natural gas in Maokou Formation in Yuanba area，compares the natural gas of adjacent formations in combination with the natural gas genetic discrimination chart，conducts gas-source correlation based on ethane carbon isotope，and analyzes the characteristics of biomarker compounds of reservoir bitumen and source rockThe genetic types and dominant source rocks of natural gas in Maokou Formation in Yuanba area are definedThe results show that:(1)The natural gas in Maokou Formation in Yuanba area has the highest content of CH4(ranging from 6760% to 9794%)，the contents of ethane and propane are both lower than 100%，there is no butane or heavier alkane gases，and the drying coefficient(C1/C1-5)is greater than 099，which is typical highly evolved dry gasThe carbon isotope of natural gas is heavier，the mean δ13C1 is -2912‰，and the mean δ13C2 is -2815‰(2)Part of the natural gas in Maokou Formation is high-maturity coal-type gas，and part is high-maturity to over-maturity oil-coal type mixed gas，showing the characteristics of mixture gas of different maturity of type II kerogen cracking gas and crude oil cracking gas(3)The δ13C2 characteristics of the natural gas in Maokou Formation are consistent with the δ13Ckerogen characteristics of the source rocks of Wujiaping and Maokou formations，and the similarity of the bitumen biomarker compounds in the reservoir of Maokou Formation to the source rocks of Wujiaping and Maokou formations indicates that the natural gas in the Middle Permian Maokou Formation in Yuanba area is a mixed source gas derived from the source rocks of Wujiaping and Maokou formations |
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