The Callovian-Oxfordian carbonate reservoirs are the most important hydrocarbon reservoir in the Samandepe gas field,Amu Darya basin,Turkmenistan.Based on the analysis of Fe,Mn and Sr trace elements,and carbon,oxygen ...The Callovian-Oxfordian carbonate reservoirs are the most important hydrocarbon reservoir in the Samandepe gas field,Amu Darya basin,Turkmenistan.Based on the analysis of Fe,Mn and Sr trace elements,and carbon,oxygen and strontium isotopes,the genesis and evolutionary characteristics of the carbonate reservoirs were studied,and the conclusions were follows：1） Sustained transgressive-regressive cycles played an important role during Callovian-Oxfordian.The reservoir of reef-bank facies was well developed in the period of transgression,while the regional dense cap rocks developed in the period of regression;2） The 87 Sr/86 Sr ratio measured from rudist shells yields an age of 157.2 Ma according to the global strontium isotope curve;3） As diagenetic intensity increased,δ 13 C changed little,and δ 18 O showed strong negative deviation but was still limited to the range of Late Jurassic seawater.High Fe and Sr contents,and low Mn content,and the evolutionary trend of δ 13 C and δ 18 O all indicate that diagenesis occurred in a relatively confined environment,where the fluids were relatively reducing and contained hot brine.The stage of diagenesis reached is mesodiagenesis,which is very favorable for preservation of primary pores in carbonates;4） Strong dissolution of reef limestones,burial dolomitization and hydrothermal calcite precipitation were all the results of the interaction between the 87 Sr-rich diagenetic fluid and rocks;5） The analysis results of isotopes,fluid inclusions and vitrinite reflectance show that the diagenetic fluid was compaction-released water that originated from the deep,coal-bearing clastic strata.展开更多
The Kutch Basin of western India is famous for its rich assemblages of the Callovian-Oxfordian ammonites.The family Oppelidae Douvillé is the second most diverse ammonite group after perisphinctids during the Mid...The Kutch Basin of western India is famous for its rich assemblages of the Callovian-Oxfordian ammonites.The family Oppelidae Douvillé is the second most diverse ammonite group after perisphinctids during the Middle-Upper Jurassic.Hecticoceratinae is the most diverse subfamily within Oppelidae and has wide palaeobiogeographic(near cosmopolitan) and temporal distributions(Bathonian-Oxfordian).Some species were well timediagnostic and thus help in interprovincial correlation.The taxonomy of the subfamily Hecticoceratinae of Kutch was in a state of flux until recently.It was not revised since Spath’s(1927-1933) great contribution.Many genera and species were morphogenera or morphospecies and they again suffer from excessive subjective splitting.It was therefore badly needed for a comprehensive taxonomic revision of the subfamily with modern aspects of systematics i.e.,sexual dimorphism and population dynamics.A lithostratigraphic framework has already been well documented in the Kutch Basin of western India.A high resolution biostratigraphy incorporating stage-intrastage fossil assemblages have been used in interbasinal correlation based on the Callovian-Oxfordian hecticoceratins.Near cosmopolitan distribution of many hecticoceratin genera were widely used for biostratigraphic zonation as well as an understanding of the palaeobiogeographic pattern.The phylogeny of the subfamily Hecticoceratinae has been used to construct the cladograms depicting area relationships among different provinces during the Callovian-Oxfordian.展开更多
文摘The Callovian-Oxfordian carbonate reservoirs are the most important hydrocarbon reservoir in the Samandepe gas field,Amu Darya basin,Turkmenistan.Based on the analysis of Fe,Mn and Sr trace elements,and carbon,oxygen and strontium isotopes,the genesis and evolutionary characteristics of the carbonate reservoirs were studied,and the conclusions were follows：1） Sustained transgressive-regressive cycles played an important role during Callovian-Oxfordian.The reservoir of reef-bank facies was well developed in the period of transgression,while the regional dense cap rocks developed in the period of regression;2） The 87 Sr/86 Sr ratio measured from rudist shells yields an age of 157.2 Ma according to the global strontium isotope curve;3） As diagenetic intensity increased,δ 13 C changed little,and δ 18 O showed strong negative deviation but was still limited to the range of Late Jurassic seawater.High Fe and Sr contents,and low Mn content,and the evolutionary trend of δ 13 C and δ 18 O all indicate that diagenesis occurred in a relatively confined environment,where the fluids were relatively reducing and contained hot brine.The stage of diagenesis reached is mesodiagenesis,which is very favorable for preservation of primary pores in carbonates;4） Strong dissolution of reef limestones,burial dolomitization and hydrothermal calcite precipitation were all the results of the interaction between the 87 Sr-rich diagenetic fluid and rocks;5） The analysis results of isotopes,fluid inclusions and vitrinite reflectance show that the diagenetic fluid was compaction-released water that originated from the deep,coal-bearing clastic strata.
基金completed under UGC Minor Research Project Scheme [F.PSW008/11-12(ERO)]
文摘The Kutch Basin of western India is famous for its rich assemblages of the Callovian-Oxfordian ammonites.The family Oppelidae Douvillé is the second most diverse ammonite group after perisphinctids during the Middle-Upper Jurassic.Hecticoceratinae is the most diverse subfamily within Oppelidae and has wide palaeobiogeographic(near cosmopolitan) and temporal distributions(Bathonian-Oxfordian).Some species were well timediagnostic and thus help in interprovincial correlation.The taxonomy of the subfamily Hecticoceratinae of Kutch was in a state of flux until recently.It was not revised since Spath’s(1927-1933) great contribution.Many genera and species were morphogenera or morphospecies and they again suffer from excessive subjective splitting.It was therefore badly needed for a comprehensive taxonomic revision of the subfamily with modern aspects of systematics i.e.,sexual dimorphism and population dynamics.A lithostratigraphic framework has already been well documented in the Kutch Basin of western India.A high resolution biostratigraphy incorporating stage-intrastage fossil assemblages have been used in interbasinal correlation based on the Callovian-Oxfordian hecticoceratins.Near cosmopolitan distribution of many hecticoceratin genera were widely used for biostratigraphic zonation as well as an understanding of the palaeobiogeographic pattern.The phylogeny of the subfamily Hecticoceratinae has been used to construct the cladograms depicting area relationships among different provinces during the Callovian-Oxfordian.
