Evaluation Of Chang 2 Reservoir In Zichang Oilfield

The XX well area of Zichang Oilfield is mainly located in Haojiagou and Yangjiagou areas of Yujiaping Township,Zichang County,Shaanxi Province.The area of the study area is about 24.6 km².The main development layers are Chang 2 and Chang 2,which are thick and rich in oil and shallow in burial.The burial depth is generally about 350-550 M.Oil wells have the characteristics of high initial production and rapid decline.In this paper,core data,thin section identification,scanning electron microscopy and other testing and analysis methods are used.Based on petroleum geology,sedimentary petrology,structural geology and other disciplines,the reservoir of Chang 2 member of Yanchang Formation in XX well area of Zichang Oilfield is described in detail.The study area is located in the middle of the Ordos Basin.Its overall structural form is a westward dip monoclinic with gentle strata and no faults.There are some slow nose-like uplifts in the study area,which have certain influence on hydrocarbon enrichment.The physical properties of Chang 2 reservoir are relatively poor.The reservoir is a set of sand and mudstone with low porosity and permeability.The physical properties of Chang 2 reservoir vary greatly due to various actions.The permeability is mainly distributed between0.4³2×10^-3?m² and the porosity is mainly distributed between 9%¹5%.One of the unique characteristics of Yanchang Formation sandstone in Ordos Basin is that its physical properties are inversely proportional to the sorting of throat,and its skewness is improved with the coarsening of grain size.The positive rhythm of each sublayer in Chang 2 reservoir is the primary rhythm mode of sand body,which is dominated by coarse to fine sediments from bottom to top.Four distributary channels were developed in Chang 2₂¹ period.The width of the channel was between 3 and 10 km,the thickness of sand body was 10 to 20 m,and the ratio of sand to ground in the main channel was more than 60%.The number,distribution area and action range of distributary channel in this period are all weakened in 2₂² periods,which indicates that the hydrodynamic force is weakened and the scale of channel is reduced.On the basis of reservoir description,the residual oil saturation of a single well in the study area is calculated by field data method,and the remaining oil distribution law of the reservoir is analyzed.