The Integrated Research On Triassic Chang 2 Oil-bearing Formation In Yuanlongsi Area

Yuan Longsi area is located in the southeast part of Yishan slope which is the biggest tectonic unit of Ordos Basin of which tectonismis apart of YiShan slope in the Ordos Basin,and itsouth central of the eastern slpoe of ShanBei,the structure of this area is relatively flat.On the basis of oil field data and analysis assay data,Chang 2 stratum is dived into three different small layers by the research method of reservoir geology and sedimentology.Then,the distribution characteristics of sand bodies and deposition microfacies will be studied following the comparing among the small layers.Integrated evaluation is based on the studies of petrologic,macro heterogeneity and micro heterogeneity.According to the methods and principles of stratigraphic division and correlation,Triassic Chang 2 oil group is divided into Chang 2~1,Chang 2~2and Chang 2~3.The data of 23 exploration wells can be used to draw superface structural forms of study area.It's a gently and widely nose-shaped uplift fits the regional tectonic setting.According to the analysis of sedimentary source,logging data and the core observation,sedimentary face can be built.The results show that Yan Chang2 oil formation of Yuan Longsi area is controled of braided delta front deposits,which developed interdistributary estuary and underwater distributary channel facies.The rock type of Change2 is arkose.Under the control of sedimentary facies belt,reservoir sand bodies distribute from NE to SW in zonal in the horizontal direction and show an overlapped feature in vertical.Porosity and permeability's distribution range is roughly evenly.Chang2belongs to low porosity low permeability reservoir.Plane heterogeneity is low while intraformational heterogeneity and inter layer homogeneity are obvious.The pore throat distribute heterogeneously.There is a a good oil source condition in Chang 2 oil group of Yuan Longsi area,with bottom generating and top storing source reservoir cap assemblage.The reservoir is defined as lithologic reservoir.There are many water layers on oil reservoir profile,and oil is located in the top of the water.