Geochemistry characteristics of carbon and oxygen isotopes of Ordovician carbonate palaeokarst reservoir in the western region of Lungu, Talimu Basin
Author(s): LIU Xiaoping, WU Xinsong, ZHANG Xiangzhong
Pages: 69-71,76-7
Year: 2004 Issue: 4
Journal: Journal of Xi'an Petroleum Institute（Natural Scien
Keyword: Talimu Basin; western region of Lungu; Ordovician carbonate rock; carbon isotope; oxygen isotope; geochemical characteristic;
Abstract: The study of the geochemical characteristics of carbon and oxygen isotopes of Ordovician carbonate reservoir in this area can provide geochemical information for understanding the genetic types, the fluid properties and the palaeohydrologic condition of karst reservoirs, and evaluating the reservoirs. The analyses of 26 matrix material samples, 6 cementing matter samples and 6 karst samples from the depth of 5 600～5 900 m show that, there is great variation of δ13C and δ18O values of the carbonate palaeokarst reservoir. The variation ranges and the average values of δ13C and δ18O are -0.70‰～-6.50‰, -3.75‰～-17.10‰ and (-1.76)‰, -9.42‰respectively. The distributions of δ13C and δ18O values of carbonate matrixes, alluvial rocks and calcite cements are different. The negative of δ18O values of three kinds of samples show that the process of carbonate diagenesis is affected by meteoric fresh water, which indicates the weathering crust karst diagenesis environment at that time. The much more negative δ13C values of alluvial rocks also indicates that their provenance is probably Carboniferous—Permian formation.
Pages: 69-71,76-7
Year: 2004 Issue: 4
Journal: Journal of Xi'an Petroleum Institute（Natural Scien
Keyword: Talimu Basin; western region of Lungu; Ordovician carbonate rock; carbon isotope; oxygen isotope; geochemical characteristic;
Abstract: The study of the geochemical characteristics of carbon and oxygen isotopes of Ordovician carbonate reservoir in this area can provide geochemical information for understanding the genetic types, the fluid properties and the palaeohydrologic condition of karst reservoirs, and evaluating the reservoirs. The analyses of 26 matrix material samples, 6 cementing matter samples and 6 karst samples from the depth of 5 600～5 900 m show that, there is great variation of δ13C and δ18O values of the carbonate palaeokarst reservoir. The variation ranges and the average values of δ13C and δ18O are -0.70‰～-6.50‰, -3.75‰～-17.10‰ and (-1.76)‰, -9.42‰respectively. The distributions of δ13C and δ18O values of carbonate matrixes, alluvial rocks and calcite cements are different. The negative of δ18O values of three kinds of samples show that the process of carbonate diagenesis is affected by meteoric fresh water, which indicates the weathering crust karst diagenesis environment at that time. The much more negative δ13C values of alluvial rocks also indicates that their provenance is probably Carboniferous—Permian formation.
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