Microscopic pore-throat structure characteristic and its influence on oil displacement efficiency in Chang-63 reservoir of Huaqing area inOrdos Basin

Through experiments on conventional mercury injection,scanning electron microscope,casting thin slice and water drive displacement test with real microscopic sandstone models,the characteristic of the microscopic pore-throat structure and its influence on the oil displacement efficiency were discussed.The results indicate the primary pore of the reservoir space is inter-granular pore and the secondary pore is dissolved pore.By applying NM-CT technology,the reservoir throats can be divided into four types:dotting throat,necking shape throat,flaky throat and sieve-tube throat.Based on conventional mercury injection and the capillary pressure curve,the pore structure can be divided into four types,namely type-I,type-II,type-III and typeIV.Different pore structures correspond to different Oil displacement efficiency and the displacement path.Permeabilityeffect on oil displacement efficiency is bigger than that of the porosity.