Sequence Characteristics Of Gaotaizi Oil-bearing Layer In Jin28 Area Of Qijia Depression

Cretaceous Qishankou Formation is the major exploration layer of Qijia depression,nowadays only three levels of the sequence of Qishankou Formation in jin28 zone of 3D project was divided and was agreed,but Division and distribution of four levels is not yet clear.In the paper we have the research on the character of four levels sequence of the Gaotaizi Formation,guided by the basic knowledge of Sequence stratigraphy and seismic sedmentology.Through identification of sequence flag and dividing layer technology by joint of Seismology and Geology,we established sequence stratigraphic framework.In the sequence stratigraphic framework we identify sedimentary facies marks and analyze sedimentary facies and distribution characteristics,then the distribution of Sand and oil and gas in the work area was included,in combine with the analysis of reservation reasons,the favorable direction of oil and gas exploration was pointed out.In the basis of Sequence boundary identification,sequence boundaries of qingshankou group and at all levels of sequence in jin28 seismic project of qijia area was normally divided,qingshankou Formation was divided to three Third-order sequence,seven Fourth-order sequence,and gaotaizi Formation was divided to five Fourth-order sequence.According to the comparasion to the Sequence Stratigraphy of main wells and seismic sequence,the characters and Controlling factors of sequence stratigraphy were analyzed.Through identification of the facies flag,logging flag and seismic flag,the single well phase and associated wells phase well were analyzed,through attribute analysis of seismic sedimentology stratal slices,the distribution of seismic facies and sedimentary facies was researched,and the location of the favorable reservoir sand bodies was predicted.Two kinds of sedimentary types was made,Lacustrine and Delta in the stratum of Qishankou Formation.Lacustrine can be divided to Semi-deep lake and deep lake;Delta can be divided to three Subphases:Delta plain,Delta front and Delta.Through the research on distribution characteristics of sedimentary facies and sand body in the framework,distribution of facies,sand,oil and gas was discussed,according to the the analysis of reservation condition,favorable exploration zone was indicated,in order to make clear direction for searching different types oil and gas reservation.