Study On Sequence Stratigraphy And Sedimentary Characteristics Of Carboniferous Carbonate Rocks In The Eastern Margin Of Precaspian Basin

The purpose of this paper is to study the carboniferous in the eastern margin of the Precaspian Basin to clarify the tectonic sedimentary evolution process,stratigraphic sedimentary characteristics and establish sequence stratigraphic framework.Thus provides the scientific basis for the subsequent exploration and development.The study area is the eastern margin of the Precaspian Basin.The target strata are carboniferous carbonate rocks.Combining field outcrops,drilling cores,logging interpretation and seismic data,based on the previous research results,on the basis of regional stratigraphic correlation,according to the sedimentary characteristics of carboniferous system in the eastern margin,the sequence stratigraphic framework of the carboniferous in the eastern margin of Precaspian Basin was established.In this paper,the genetic types and spatial and temporal distribution of carboniferous reservoir sand bodies in the eastern margin are studied,and the sedimentary facies(microfacies)types and sedimentary characteristics of the carboniferous reservoir sand bodies in the eastern margin of the Precaspian Basin are determined.Studies have shown that the tectonic evolution stage that has important influence on the Precaspian Basin is Devonian-Carboniferous back-arc basin stage and Permian foreland basin stage,its tectonic evolution was influenced by the closure of the Urals ocean in the eastern margin and the subduction and subduction of the palaeo-asian ocean and the palaeo-tethys ocean in the southern margin during the same period,sedimentary evolution is also significantly influenced by changes in global sea level at different levels.In detailed divided the eastern margin of the carboniferous sequence interface and its internal system domain,on the basis of combining the method of classic sequence stratigraphy theory,single well sequence stratigraphic characteristics in the study area is studied in detail,studies have shown that the carboniferous of the eastern margin of the Precaspian Basin is divided into eight secondary sequence,nineteen tertiary sequence and established the carboniferous sedimentary model,the second sequence is named after its corresponding order and third sequence are named after their corresponding small levels.On the basis of sequence and sedimentary studies,the relationship between sequence and reservoir cover assemblage is studied,it is believed that there are two sets of sequence-related reservoir and cap assemblages in the carboniferous system at the eastern margin of the Precaspian Basin.The first set of reservoir and cap assemblages is lower carboniferous KT-II limestone or dolomite(reservoir)-middle carboniferous MKT mudstone(cap).The second set is carboniferous middle-lower series KT-I limestone or dolomite(reservoir)-Permian lower series mudstone(cap).The study of carboniferous tectonic-sedimentary evolution,the establishment of sequence framework and sedimentary facies in the eastern margin of the Precaspian Basin can provide scientific basis for subsequent exploration and development.