The Traps Prediction And Evaluation Of Silurian Kepingtage Formation In The East Of Tarim Basin

Tarim Basin,as the biggest onshore petroliferous sedimentary basin in our country,is the important strategic base in the West-East natural gas transmission project.The great hydrocarbon breakthroughs in Silurian Kepingtage Formation stratum of Tarim Basin have been achieved in the recent years of exploration,which makes the research of Silurian hydrocarbon a hotspot.Under the controlling of the tectonic movements in Caledonian period and early Hercynian,the Silurian stratum were corroded in the ridgy zone,which provide the favorable condition for the formation of the tectonic and stratigraphic traps.Therefore,the investigation has been developed with the purpose of the recognization and evaluation of the traps of Silurian Kepingtage Formation stratum in the western slope of Manjiaer depression and Mandong tectonic belt.On the basis of core information,logs and seismic data,under the guidance of sequence stratigraphy,seismic stratigraphy and sedimentology the research work including sequence stratum division,sedimentary facies and reservoir-cover assemblages in Kepingtage Formation has been developed.First,the sequence stratigraphy framework has been established with the integrated study of logs and seismic data.Secondly,the sedimentary facies in every sequence have been analyzed after the research of the log facies and the seismic facies.Finally,based on the systematical study and summation of the reservoir-cover assemblages in Kepingtage Formation,the tectonic and stratigraphic traps are evaluated.The achievements can be described as follows:1.Sequence stratigraphic framework of Kepingtage Formation in the research area has been maked clear.The Kepingtage Formation is divided into three third-order sequences.The rising and descending base level cycle is distinguished in every sequence.2.Every sequence in Kepingtage Formation is well developed in the Manjiaer depression and is lost in the around slope zone.Sql stratum is the smallest,which is corroded in the east and north-west and overlaps on the underlayers in the south.Sq2 and Sq3 stratum are corroded in the east and the south.3.Four types of seismic facies are summarized according to the seismic characteristics of Kepingtage Formation.On the basis of geologic data analysis and seismic facies interpretation the distribution of sedimentary facies in the sequence framework were clear.4.The thickness of every shale cover has been predicted after the analysis of the forward model which indicated the effection of different shale thickness.5.In the three sequence of Kepingtage Formation three reservoir-cover assemblages are summed up.The upper and the lower assemblages are favorable in the western research area and in the eastern area the upper assemblage is optimum.6.There are eleven tectonic traps,six stratigraphic overlap traps and t:hree stratigraphic unconformity barrier traps in Sql stratum of Kepingtage Formation.Twelve tectonic traps and two stratigraphic unconformity barrier traps are recogonized in the Sq2 stratum,and twelve tectonic traps and three stratigraphic unconformity barrier traps are found in the Sq3 stratum.After the synthetic evaluation,as to Sql stratum the stratigraphic overlap traps in the western area of Well Mancan 2 are favorable.The stratigraphic unconformity barrier traps of Sq2 and Sq3 stratum in the area of Well Mannan 1 are also advantageous.