Study On The Interlayers Of The Braided River Reservoir In The Qigu Formation,Nine 8^th Area,the Northwest Margin Of Junggar Basin

Nine area of Karamay oilfield is located in the overlap pinchout belts of the the hanging wall of the Ke Wu fault zone in the northwest margin of Junggar basin.The Qigu Formation reservoir in nine 8^th area is located in the northwest of nine area.The Jurassic Qigu Formation is the main oil-bearing section,which is a braided river sedimentary system.The channel migration and swing are frequent,and the interlayer development and spatial distribution are complex,which seriously restricts the thermal recovery and development effect of heavy oil.In order to solve the contradictions in the current development process of the oilfield and lay a foundation for the follow-up well location optimization and adjustment of the oilfield,this paper takes the internal interlayer of the braided river reservoir in the Qigu Formation of nine 8^th area of Junggar Basin as the research object,combines the core,logging,and production performance data,and starts with the stratigraphic correlation and sedimentary microfacies description,and develops a comprehensive study of the braided river reservoir in the research area on the genetic type,identification mark,spatial distribution and the distribution of remaining oil in heavy oil thermal recovery.The study shows that Qigu Formation can be divided into three sand groups vertically,and J₃q₂ sand group can be further divided into three single layers and eight single sand bodies.The target zone is a sandy braided river distributed from north to south,and the main sedimentary microfacies are river channel,channel bar and flood plain.There are two types of interlayer:muddy interlayer and physical interlayer.The main lithology of muddy interlayer is mudstone,silty mudstone and muddy siltstone,which has the characteristics of"high gamma,low resistance and medium density".The genesis is flood plain deposit,gully at the top of the channel bar and the deposition layer inside the channel bar,which is distributed on the top of the reservoir sand body vertically,thin and discontinuous horizontally,and mostly in the north of the study area;the main lithology of the physical interlayer is sandy conglomerate.It has the characteristics of"high gamma medium resistance and high density".Its genesis is river channel glutenite body and glutenite body at the bottom of the channel bar.It is mainly distributed in the inner and bottom of the reservoir sand body vertically,and it is inclined to the sand body laterally.It is thick and has good continuity.It is the main interlayer in the work area.The smaller the number of interlayers are,the higher the connectivity is,the better the permeability is,and the more abundant the remaining oil will be.The results of this paper provide a direct geological basis for the later well location deployment and oil recovery improvement.