Research On Sedimentary Facies Of The Lower Member Of Jiufotang Formation In Luxi Sag

The structural oil and gas reservoirs in the lower part of the Jiufotang Formation in the Luxi Depression have been basically proved,and the lithology and lithology-tectonic reservoirs are the next exploration priorities.However,due to the limitations of the understanding of the spatial distribution of sedimentary faeies,the subsequent exploration process is restricted.In this paper,focus on the sedimentary characteristics of the Jiuxia section of the Luxi Sag,guided by related theories,make full use of existing materials,through a variety of research methods,detailed study of sequence stratigraphic division,petrological characteristics,sedimentary facies types and sedimentary facies distribution characteristics,summed up the evolution law of sedimentary facies,established sedimentary facies model,and phase of advantage is analyzed and described.In this paper,the Jiufotang Formation is divided into one sequence with three systems tracts,while the lower part of Jiufotang and the upper part of Jiufotang are separated by the MFS,and the lower part of Jiufotang formation contains two systems tracts(lowstand systems tract and transgressive systems tracts).and further subdivided into seven parasequence sets.Through the seven well sections,the isochronous stratigraphic framework of the lower part of the Jiufotang Formation in the Luxi Sag was established.Four facies were identified in the lower part of Jiufotang formation.Types and their corresponding subphases and microphases,and their characteristics are described in detail.Through the analysis of single well sedimentary facies and the comparison of the sedimentary connected wells in the whole area,it is believed that the Wushijiazimiao depression in the study area is mainly dominated by lakes,and both deep lakes and shallow lakes are developed.The eastern steep slopes mainly develop slip turbidite fan.The Majiapu high barrier zone develops a typical fan delta;the Mabei slope zone develops a braided river delta.The planar distribution characteristics and evolution laws of the sedimentary facies of each sequence in the lower part of the Jiufotang formation are analyzed.It is considered that the microfacies of the underwater river channel and the granulating beach micro facies are the dominant reservoir facies belts,and the reservoir physical properties and thickness distribution are better,which is the key direction of oil and gas exploration in the next step.