准噶尔盆地车排子凸起多物源复杂沉积体系中的地震沉积学

Seismic Sedimentology in Multiple Sources-Complex Depositional Systems of Chepaizi Uplift,Junggar Basin

准噶尔盆地车排子凸起新近系沙湾组为湖盆缓坡多物源、复杂沉积体系沉积,其沉积体系认识争议很大,时空演化难以刻画.准确刻画其沉积体系类型、演化规律和砂体分布特征,是精细刻画单砂体及内部构型等储层的基石,对后期油气开发具有重要指导意义.在岩心、测井、测试分析及地震资料,充分利用相位转换、地层切片等地震沉积学技术方法,对其沉积体系特征进行深入研究.建立研究区精细层序地层格架,将沙湾组划分为2个三级层序、4个四级层序;识别出冲积扇、辫状河、曲流河、曲流河三角洲、扇三角洲及滨浅湖6种沉积体系类型,并确定沉积体系边界及演化规律;建立了多物源冲积扇-辫状河、扇三角洲-曲流河三角洲沉积模式及砂体分布模式.辫状河道、心滩、点坝复合体及冲积扇砂体均钻遇较好油气显示,为重要储集体.此次研究丰富了地震沉积学在湖盆缓坡多物源、多沉积体系类型中的应用.

The Neogene Shawan Formation from the Chepaizi uplift of the Junggar basin,has multiple sources and complex depositional systems.It has long been debated about the depositional systems due to limited well and core data.Besides,it is hard to depict the spatial and temporal evolution.The depositional system is the key to depict the single sandbody and its architecture,which has a profound meaning for hydrocarbon exploration.Based on 3 Dseismic data,core data and well logs,combined with the seismic geomorphology approach,the depositional systems and evolution history of the Neogene Shawan Formation in the Chepaizi uplift of the Junggar Basin were studied in great detail.A sequence stratigraphy framework was established.And,two third-order sequences,namely,sequences NSQ1 and NSQ2 from base to top,and four forth-order sequences were identified from the Shawan Formation.Six depositional systems,namely,braided river,alluvial fan,meandering river,meandering river delta,fan delta and shallow lacustrine systems,were identified.Then,two sedimentary models,namely,alluvialfan-braided river systems and fan delta-meandering river delta systems,were built in the study area.Finally,the prediction model of sand bodies was constructed.There has showed significant indication of oil and gas in the sand bodies of braided rivers,mid-channel bars,point bars,and alluvial fan.So,they are the primary reservoirs in study area.It is proved that seismic sedimentary is a useful approach applied in multiple sources,complex sedimentary systems in gentle slope of lacustrine basin when core data and well data are limited.