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高校地质学报 ›› 2022, Vol. 28 ›› Issue (5): 717-725.DOI: 10.16108/j.issn1006-7493.2021113

• 南海海洋地质、构造与油气资源专辑 • 上一篇    下一篇

莺歌海盆地东斜坡超高压气田天然气地球化学特征差异与成因

郭潇潇,徐新德,甘 军,熊小峰,汪紫菱,游君君   

  1. 中海石油(中国)有限公司湛江分公司,湛江 524057
  • 出版日期:2022-10-20 发布日期:2022-10-20

Causes of Gas Geochemical Differences in the Ultra-high Pressure Gas Field, the Eastern Slope of Yinggehai Basin

GUO Xiaoxiao,XU Xinde,GAN Jun,XIONG Xiaofeng,WANG Ziling,YOU Junjun   

  1. Zhanjiang Branch of CNOOC Ltd., Zhangjiang 524057, China
  • Online:2022-10-20 Published:2022-10-20

摘要: 近年来,在南海北部莺歌海盆地东斜坡南部勘探取得重大进展,发现了超高压高温L气田。但针对该气田内部天然气地球化学特征差异及其成因等问题研究较少,制约了本区勘探的进展。文章基于天然气地球化学数据,结合区域石油地质条件、烃源岩特征及包裹体分析等资料初步揭示天然气的类型和气藏差异成因。从天然气地球化学特征上看,L气田中L1、L2和L3气藏天然气地球化学特征在天然气干燥系数及重烃碳同位素值组成等方面差异较大。尽管天然气均为煤型气,但可依据甲烷、乙烷及丙烷碳同位素值及δ13C1-δ13C2等参数细分为M型和S型,M型主要与梅山组烃源岩有关,S型主要来自三亚组;从不同类型天然气的分布看,从近凹中的L1气藏至近隆的L3气藏,天然气类型由既有M型也有S型转变为以S型为主,这一差异与烃源岩生烃过程、气藏的空间位置及垂向充注过程密切相关;从气藏形成过程看,凹陷斜坡南部梅山组和三亚组烃源岩在全新世进入高过成熟阶段;近凹一侧梅山组和三亚组烃源岩生成的天然气沿断裂进入黄流组成藏,形成L1气藏,近隆一侧三亚组天然气进入梅山组二段成藏形成L3气藏。

关键词: 天然气, 地球化学特征, 成因类型, 超高压高温, 莺歌海盆地

Abstract: Recently, important exploration discovery of natural gas has been obtained in the eastern slope of Yinggehai Basin. Ultra high pressure and high temperature gas field L has been found. There are few researches on the differences of geochemical characteristics and the origin of natural gas in the this gas field, which restrict the exploration progress in this area. This work exhibits a comprehensive understanding of source rock sedimentation, inclusion and detailed gas geochemistry to study the formation of natural gas discovered. It is concluded that the geochemical characteristics of gas in L1, L2 and L3 gas reservoirs in gas field L has significant differences. Although the natural gas is coal type, it can be subdivided into M type and S type according to the carbon isotope values of methane, ethane and propane and δ13C1-δ13C2 parameters. Secondly, viewed with the distribution of different types of natural gas, from the near depression center L1 gas reservoir to the near uplift L3 gas reservoir, the natural gas types changed from both M-type and S-type to S-type. This difference is closely related to the hydrocarbon generation process of source rock, the spatial location of gas reservoir and the vertical charging process. Finally, from the formation process of gas reservoirs, the source rocks of Meishan Formation and Sanya Formation entered the maturation or over-maturation stage in the Holocene. On the near depression center side, the gas generated from Meishan formation and Sanya formation migrated to L1 gas reservoir in the Huangliu formation through faults and micro faults, while, on the near uplift side, the gas generated from Sanya formation migrated to L3 gas reservoir in the second member of Meishan formation.

Key words: natural gas, geochemical characteristics, genetic type, ultrahigh pressure and high temperature, Yinggehai Basin

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