Study On Sedimentary Facies In The Upper Submember Of The Third Member Of Shahejie Formation In Dongfenggang Oilfield

Turbidite reservoir of the upper submember of the third member of Shahejie Formation is one of the main reservoir type in the Dongfenggang Oilfield.Despite positive results in oil exploration and development in blocks,such as Che40-44,Che142-6,Che40-31-x35,and Che407-1,the problems of frequent turbidite fan migrating,complex sand body distribution,and high density well spreading outside the target blocks leads to,incomprehensive understanding and more work should be done,isochronous stratigraphic framework establishing,systematic regional sedimentary laws building,the sedimentary model forming,to better determination of the exploration targets in this oil fields.As a result,this paper take the turbidite fan of Sha-3 upper sub-member,a major blocks of Dongfenggang Oilfield,as the research subject.Based on previous study of Che40-44 block,with the help of drilling data,well logs,seismic data and laboratory test analysis etc.,this research develops the isochronous stratigraphic division and correlation,determines turbidite sand body sedimentary characteristics,types and its distribution.The results are as following:(1)Guided by stratigraphy and sedimentology knowledge,with the aid of geophysical data,this study established the stratigraphic classification and correlation in the upper sub-member of Sha-3.It is divided into 4 sand bed sets and 26 layers.We determined the top boundary,achieved the region layer unification under the sequence stratigraphy restrain,and established the isochronous stratigraphic framework;(2)This research proposed that turbidite fan sedimentary system is mainly supplied by feeder channels which are developed on the gentle slope of fault trough lake basin in Sha-3 upper sub-member of this area.Turbidite fan can be divided into channel-presence and channel-absence.,Channel-presence turbidite can be divided into main channel,inter main channel,braided-channel in middle fan,inter braided channel in middle fan and sand lobate;(3)Combining geophysical technique and geological analysis,this research clarified the turbidite fans distribution,and established sedimentary facies model.There are four phases turbidite fans developed in upper sub-member of Sha-3,whose scale gradually increase from bottom to top.Sediment prograde along the provenance direction and frequent migrate laterally in vertical source direction,resulting in,relatively poor continuity in lateral direction;(4)This study clarified the genetic types of sand body and its distribution.Lake level changes,tectonic movement and sediment supply are the main controlling factors of sand body distribution.We proposed four favorable area for the next round of rolling exploration and development.The results are of great significance for guiding and deepening the understanding of the exploration in the target area.