Seismic Stratigraphic Division And Seismic Facies Study In The Jilantai Area Of The Hetao Basin

The Jilantai area is located in Linhe depression,southwest of Hetao Basin.The lower Cretaceous is the main exploration target system.At present there are only 3 wells in this area.Only one of them have been discovered in crude oil.It is of the great significance for the stratigraphic division,sedimentary facies and seismic facies identification in the lower Cretaceous of the study area,with the basin entering the third exploration stage.In this paper,the lower Cretaceous Guyang formation is divided into three sections through lithology,paleontology and sedimentary cycles in the Jilantai area.We also made seismic synthetic records of ST1?ST2 and JC1 well,and identified the unconformity at the top of Guyang formation and the third segment of Guya ng formation,the bottom of Guyang formation and the top and bottom of the Linhe formation.The Guyang formation was traced and the lower Cretaceous framework was established.From the comparison with the Ordos Basin?Bayanhaote Basin and Yine Basin,It is considered that the Cretaceous system has the isochronous significance.From analyzing the logging curve characteristics of ST1,ST2 and JC1 well,combined with the previous analysis of sedimentary characteristics,the sedimentary facies of three wells are divided.The second and third segment of Guyang Group have the characteristics of dryland fan deposition,and the fist segment is Lacustrine deposition.There are two sets of dark mudstones developed in the first section,which contain a lot of calcite and dolomite,and well logging was shown to be high gamma value,high density value and low acoustic value.The third segment is displayed a wedge body in some sections.The ZK500 drill has drilled into the wedge,It is a set of near source coarse sediments.A high aeromagnetic anomaly body is developed in the northwestern part of the basin.Its uplift at the end of the third segment the sedimentary period leads to the transformation of the basin's fault depression to the depression The thinning of the second segment and its later sediment thickness to the direction of the fault.The wave impedance of the dark mudstone is greater than that of sandstone in the first segment,and the sandstone wave impedance of sandstone is greater than that of dark mudstone in the second-third segment.The dark mudstone and limestone showed a trough of two peaks on the seismic profile,the thickness and the amplitude is positively correlated.In the study area,there are four types of seismic facies:dark mudstone continuous,medium and strong amplitude seismic facies;continuous,medium amplitude seismic facies in the limestone;random and blank reflection seismic facies in the wedge body;subparallel weak amplitude seismic facies.The amplitude attributes of the three segment of Guyang group were extracted,and three regions of strong,medium and weak were divided into different types of sedimentary facies.According to the analysis of rock physical properties,reservoir caprock and migration,and by making the dark mudstone thickness map of the study area,the favorable exploration area is briefly divided.