西南石油大学学报(自然科学版)

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Carbon and Oxygen Isotope Stratigraphy Research in Chashgui Area

Wang Qiang1,2, Wang Xingzhi1, Xu Jianliang2, Liu Bin3, Zhang Qin2   

  1. 1. School of Geoscience and Technology,Southwest Petroleum University,Chengdu,Sichuan 610500,China
    2. Geologic Exploration & Development Research Institute,Chuanqing Drilling Engineering Co. Ltd.,CNPC,Chengdu,Sichuan 610051,China
    3. CNPC(Turkmenistan)Amu Darya River Gas Company,Dongcheng,Beijing 100011,China
  • Online:2014-06-01 Published:2014-06-01

Abstract:

The effective reservoir in Chashgui Area,Turkmenistan,is Callovian–Oxfordian carbonate rocks. Since the GR
curve does not varies much,it is difficult to predict the favorable reservoir distribution. Using the carbon and oxygen isotope
from the 41 samples out of the core of the Well Cha-21 in Chashgui Area,combining with the data of the sedimentary evolution,
this paper discusses the sea-level changes during the sedimentation of the Callovian–Oxfordian reservoirs. It is shown that the
information in the oxygen isotope has been damaged,and the information in the carbon isotope has been preserved. So the
carbon isotope can be used to study the isotope stratigraphy and analyze the Palaeo-environment. The calculated salinity index
is 128.25~136.63,which is higher than the division standard between brine and freshwater,so the diagenetic fluid is high
salinity brine. The carbon-isotope stratigraphic curve is almost consistent with the global sea-level curve,which proved that
the reservoir geologic period is really Callovian–Oxfordian. According to the sea-level change curve,the main reservoirs
in Callovian–Oxfordian are divided into 3 sedimentary cycles and 5 evolutionary phases. Those results fill up the blank in
the isotopic stratigraphy studies,which are important significance for the in-deep understanding of the law of sedimentary
evolution,and predicting the favorable blocks.

Key words: isotopestratigraphy;sedimentary cycle;Callovian&ndash, Oxfordian;Chashgui Area;Turkmenistan