石油学报 ›› 2012, Vol. 33 ›› Issue (1): 55-63.DOI: 10.7623/syxb201201007

• 地质勘探 • 上一篇    下一篇

四川盆地须家河组地层水微量元素与氢氧同位素特征

李 伟  秦胜飞   

  1. 中国石油勘探开发研究院提高石油采收率国家重点实验室 北京 100083
  • 收稿日期:2011-06-12 修回日期:2011-09-02 出版日期:2012-01-25 发布日期:2012-03-22
  • 通讯作者: 李 伟
  • 作者简介:李 伟,男,1963年2月生,1987年毕业于江汉石油学院,2004年获成都理工大学博士学位,现为中国石油勘探开发研究院高级工程师,主要从事油气成藏、油气田水文地质、石油与天然气地质综合评价与勘探实践研究。
  • 基金资助:

    国家重大科技专项(2008ZX05001-05-03)资助。

Characteristics of trace elements and hydrogen and oxygen isotopes in the formation water of the Xujiahe Formation, Sichuan Basin

LI Wei QIN Shengfei   

  • Received:2011-06-12 Revised:2011-09-02 Online:2012-01-25 Published:2012-03-22

摘要:

近几年,四川盆地上三叠统须家河组发现了大量天然气,同时也发现其普遍存在高矿化度的地层水。这些地层水不仅具有常量离子发育的特殊性,也具有稳定同位素与微量元素分布的特殊性。利用GV IsoPrime II型稳定同位素质谱仪,对四川盆地二叠系—侏罗系的地层水进行氢氧同位素分析,建立了川中—川西地区二叠系—侏罗系的稳定同位素蒸发分馏趋势线,为该区地层水成因的判别确立了初步标准。受雷口坡组盐膏层的影响,雷口坡组三段—四段及其以上的陆相地层水同位素蒸发分馏演化特征是以δD快速加重为主,而雷口坡组二段及其以下的海相地层水同位素演化特征是以δ18O 快速加重为主。须家河组地层水是由雷口坡组上部高盐度地层水与须家河组沉积后埋藏压释水混合变质而来;同时,须家河组部分气田水中还存在较多的凝析水,凝析水的存在也指示须家河组有过强烈抬升与水溶气的脱溶成藏事件。

关键词: 四川盆地, 须家河组, 地层水, 凝析水, 微量元素, 氢氧同位素, 地质意义

Abstract:

Large quantities of natural gases have been found in the Upper Triassic Xujiahe Formation of the Sichuan Basin in recent years. At the same time, formation water with high salinity was also found widespread in the Xujiahe Formation and it contains not only the particularity of constant ion development, but also particularity of stable isotopes and trace element distributions. This paper established an evaporation-fractionation trend line of stable isotopes for the Jurassic to Permian systems in the middle-western Sichuan Basin, and preliminarily determined standards to discriminate origins of formation water in the study area. Influenced by gypsum-salt layers in the Leikoupo Formation, the isotopes evaporation-fractionation evolution of formation water was characterized by the dominance of a rapid increase of δD and δ18 O values, respectively, for Jurassic to the 3rd member of the Leikoupo Formation and the 2nd member of Leikoupo Formation to Permian. The formation water in the Xujiahe Formation was identified to be a metamorphic mixture of the high-salinity formation water from the upper Leikoupo Formation and the depositional water excreted by compaction after the burial of the Xujiahe Formation. Meanwhile, some gasfield water of the Xujiahe Formation was found to contain a considerable amount of condensate water, and the presence of this condensate water might also indicate a strong uplift of the Xujiahe Formation and some gas-accumulation events by exsolution of water-soluble gases.

Key words: Sichuan Basin, Xujiahe Formation, formation water, condensate water, trace elements, hydrogen and oxygen isotopes, geological significance