The Study On Fine Geological Characteristics Of Chang 8 Reservoir In Huanxian FS Area,Ordos Basin

Huanxian oil area is located in west-central Ordos basin,in which there are rich shallow water sedimentary characteristics in Mesozoic Triassic Yanchang group chang 8,develop shallow water delta deposits,is the main hydrocarbon-bearing layer.Due to the factors such as limited technology and less logging data,the geological understanding of chang 8 reservoir on Huanxian FS area has some limitations,cannot meet the needs of oilfield continue development.Therefore,developing the fine geological study in the study area is particularly important to serve the late oilfield development programme.This paper research the chang 81 of Yanchang group in Huanxian FS area.Layer fine division and correlation,sand body distribution features and sand top micro-structure research,sedimentary facies research,logging evaluation with constrainted geological conditions,reservoir heterogeneity characteristics research,reservoir parameter distribution characteristics research,reservoir classification evaluation research have been carried out based on the collection of geological information,core information,logging information and the production dynamic information in the area.Research shows that the chang 81 formation can be divided into three small layers,chang811,chang 812,and chang 813.Structure in the study area shows low in the west and high in the east,develop small nose-like uplift structure with inheritance,but in different period,its distribution features has slight different.From the plane distribution figure of sand body thickness,the chang 813 sand body develop very thin,show banding,the chang 812 sand body develop best,show "H" shape,the most thick position of sand body over 14 meters.The research area is delta front subfacices,chang 812 deposition period mainly develop underwater distributary channel deposition,underwater distributary bay and underwater natural levee is locally develop in northeast and southwest direction of research area,chang 811 deposition period mainly develop underwater distributary channel deposition in the central of the research area,northwest are mainly develop underwater distributary bay deposition,northeast locally develop underwater distributary bay and underwater natural levee.The porosity of chang 81 in study area are mainly distributed in 10%-16%,the average porosity is 12.8%,the permeability of chang 81 are mainly distributed in(0.5-5)×10-3?m2,the average permeability is 0.84×10-3?m2.The porosity,permeability,and oil saturation in the study area has good correlation,reservoir parameter distribution characteristics has good correspondence with sand thickness and deposition microfacies.The chang 811 has stronger heterogeneity than chang 812 in chang81 reservoir.Using cluster analysis method and discriminant function analysis method,select porosity,permeability,oil saturation,sand thickness,and sand ground rate five parameters as the parameters of the reservoir classification evaluation,reservoir can be divided into four classes:?,?,?,?.To carry out and complete this paper is particularly important for the next oil field development plan formulation.