Study On Chang 4+5 Formation Reservior Heterogeneity Of Jihuang 32-Xiao Jianzi Area

Taking the Chang 4+5 formation of Jihuang 32-Xiao jianzi area in Ordos Basin as the research object,combining regional geological data and previous research results,with the integration of drilling,logging and analytical test data,using traditional cycle contrast,uniform thickness contrast methods,based on the methods like reservoir's 3D geological modelling and numerical modelling,the research of Chang 4+5 reservoir heterogeneity has been finished and the results are as follows:(1)Chang 4+5 oil bearing formation includes four small layers like Chang 4+522,Chang 4+521,Chang 4+512,and Chang 4+511.The research area is a monocline with west gentle dip,and locally developed near east-westward nose structure.Its sedimentary facies belongs to the delta front sub-facies,with northeast main provenance direction and northwest secondary provenance direction.Two main sedimentary microfacies are identified including sub-water channels and interdistributary bay;while microfacies like sub-water levee,channel mouth bar,crevasse splay are not developed.Chang 4+522 small layer has the thickest sand body,about 10 meters average thickness,in study area,and its distribution is controlled by sedimentary microfacies.(2)The lithology of Chang 4+5 reservoir includes lithic feldspathic sandstone,feldspathic lithic sandstone,and it has poor reservoir quality like low porosity and extra-low permeability.Using porosity,permeability,and permeability variation coefficient and mercury data to study reservoir heterogeneity,the results show that the study area has medium inner layer heterogeneity,weak to medium interlayer heterogeneity,relatively strong to strong flat heterogeneity,and weak to medium microcosmic heterogeneity.Intercalation distribution model of Feng 8 and Jian 9 close well spacing area is built.(3)Chang 4+5 reservoir of oil-bearing group was analyzed to calculate geological reserve,evaluate reserve abundance of every reserve unit.The evaluation results show that Chang 4+522 small layer of Jian 9 well area has large reserve and high reserve abundance,belonging to II1 reserve abundance type;reservoir heterogeneity affects the horizontal and lateral distributions of oil and gas,and the areas with good reservoir quality and weak reservoir heterogeneity have relatively high oil-bearing property;and reservoir permeability affects waterflooding results:when the permeability is equal to or less than 0.75 md,the waterflooding results are poor,the formation pressure decreases largely,and the formation energy will be insufficient.