塔里木盆地塔中地区下奥陶统白云岩的成岩流体演化: 来自团簇同位素的证据

Translated title of the contribution: Diagenetic fluid evolution of dolomite from the Lower Ordovician in Tazhong area, Tarim Basin:Clumped isotopic evidence

Jiaqing Liu, Zhong Li, Mengke Yan, Peter K. Swart, Liu Yang, Chaojin Lu

Research output: Contribution to journalArticle

Abstract

Based on the relationship between the relative abundance of 13C and 18O bonds and temperature, carbonate clumped isotope (Δ47) has the special characteristic of indicating temperature even in the absence of knowledge about the chemical and isotopic composition of the fluid from which the carbonates precipitated.This property hence makes the technique an excellent temperature proxy in the study of diagenetic fluids.As such, this study employs clumped isotopes to examine the origin of diagenetic fluids in deep and ultra-deep subsurface settings and we assess their impact on the development of reservoir quality.This study considers both the matrix and associated cements.Three episodes of diagenesis are revealed. In the first stage, the fluids formed in a shallow-to-medium burial environment and the matrix was altered to have a powder-crystal to finely-crystalline texture.The range of Δ47 derived temperatures ranges from 69 to 94℃, and the δ18Ow values are from +1.81‰ to +5.19‰ SMOW.These data suggest that the fluid is modified seawater.The second diagenetic episode was influence by a brine after the sequence was deeply-bured.Here, the matrix was altered to a me-dium-crystalline texture and the Δ47 derived temperatures range from 111 to 113℃, and the δ18Ow values range from +8.46‰ to +8.95‰ SMOW, indicating that a substantial water-rock interaction occurred.The third diagenetic episode was induced by hydrothermal fluids, likely travelling along faults and fractures, which yielded abundant saddle dolomite.Here, Δ47 derived temperatures varies from 130 to 147℃ and the δ18Ow values from +7.93‰ to +9.42‰ SMOW.The vug- and vein-filling carbonates have a wide range of δ18Ocarb and δ13Ccarb values.The δ18Ocarb values span -17.38‰ to -5.84‰ VPDB, and the δ13Ccarb values from 3.57‰ to -1.33‰ VPDB, indicating multiple stages of fluid modification.Both the cores and photomicrographs demonstrate excellent reservoir quality for the Lower Ordovician Tazhong dolomites.

Translated title of the contributionDiagenetic fluid evolution of dolomite from the Lower Ordovician in Tazhong area, Tarim Basin:Clumped isotopic evidence
Original languageChinese
Pages (from-to)68-82
Number of pages15
JournalOil and Gas Geology
Volume41
Issue number1
DOIs
StatePublished - Feb 28 2020

Keywords

  • Carbonate
  • Clumped isotope
  • Diagenetic fluid
  • Dolomite
  • Lower Ordovician
  • Reservoir
  • Tarim Basin
  • Tazhong area

ASJC Scopus subject areas

  • Geology

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