Analysis Of Sedimentary System And Prediction Of Favorable Exploration Target Of Xingouzui Formation In Jiangling Depression, Jianghan Basin

Jiangling Depression is the largest subbasin in Jianghan Basin, developed on the Meso-Cenozoic basement.With the guidance of the theory of Sequence Stratigraphy, seismic sedimentology and geomorphology, and based on 3D seismic data, well loggings, cores and geochemical data, isochronous stratigraphic framework of Xingouzui Formation were established, types of sedimentary facies were recognized, the distribution and evolution of sedimentary facies zones were illustrated, the deposit source and the control effect of paleogeomorphic enviroments on sedimentary system were discussed, and the favourable exploration targets were revealed.Xingouzui Formation is a second-order sequence and there are four third-order sequences, SQXS, SQXXI, SQXXII, SQXXIII. During the deposition peroid of Xingouzui Formation, fluvial-delta plain, delta front, shore-shallow lacustrne, shallow lacustrine, semi-deep lacustrine, salt lacustrine were divided. From SQXXIII to SQXXI, it is a process of transgression to regression. There are mainly fluvial and fluvial delta in the north, northwest, west of Jiangling Depression, dalta and shallow lacustrine in the middle of the depression, shore-shallow lacustrne and salt lacustrine in the south.The deposit source were revealed by field outcrops, dip logging, the components and content of heavy minerals, compositional maturity of the rocks, seismic attribute and seismic reflection structure.During the deposit period of Xingouizui Formation, there are three deposit sources: Nanjing water system, from the north of the basin, Zhijiang water system, from the northwest of the basin, Yuan’an water system, from the west of the basin.The control effect of paleogeomorphic enviroments on sedimentary system were discussed. Jingzhou Antcline Belt was an underwater uplift, and it was a barrier to water system. Wancheng Fault was a contemporaneous sedimentary fault, and the sedimentary model of slope break was developed in the downthrown side. The Meihuaiqiao Sag and Huduhe Sag was present in this deposition period, and they were the unloading zones of the sediment.Based on the analysis of sedimentary system and the hydrocarbon source rock distribution, three favourable reservoir facies belts were put forward, downthrown side of Wancheng Fault, the south slope zone of Jingzhou anticlinal belt, the south slope zone of Zifusi Syncline.