Pore Structure And Flowing Characteristics Of Chang8Reservoir In Zhangjiashan-Gengwan Area,Ordos Basin

Based on the previous researches, Using the real sandstone micromodel to perform an experiment of microscopic waterflooding in Chang8reservoir in zhangjiashan-Gengwan Area,Ordos Basin and combining with collected information and a series test analysis data(thin-section, physical property analysis, scanning electron microscopy, relative permeability and mercury intrusion),It is analysed that pore structure affect the distribution of oil-water and recovery and relationship between pore structure and the water driving efficiency, Discussing the main factor which control water oil displacement efficiency.Reservoir of micro-pore type and structural characteristics as following:reservoir rock develops intact intergranular pore, remaining intergranular pore, slit-like intergranular pore, intragranular pore of matrix (mainly intergranular pore of authigenic kaolinite), fracture pore, corroded intragranular pore (feldspar corroded grain pore), pore type,etc. It is the most important the type of the combination of slit-shaped intergranular pore-microcrack in clast and cement-corroded intragranular pore-intergranular pore in study area. Pore structure is divided into ⅡA low-to-moderate expulsion pressure type (accounting for9.09%of the total samples), ⅡB moderate-to-high expulsion pressure type (48.86%), ⅢA high expulsion pressure type (32.95%), ⅢB ultra-high expulsion pressure type (9.09%), of which IIA low-to-moderate expulsion pressure type and ⅡB moderate-to-high expulsion pressure type are major pore structure type of the reservoir in study area Studing on the areal heterogeneity, the interlayer heterogeneity, the in-layer heterogeneity and microscopic heterogeneity,it shows that the overall heterogeneity of Chang8reservoir is strong, especially, significant micro-heterogeneity is the most important factor which is resulted in the outcome of different waterflooding experiment.Chang8reservoir displacing type is divided into three types that are homogeneous, reticular and finger-like displacement, final displacement efficiency from homogeneous to finger-like displacement changes to worse.Through research and analysis of the oil-water relative permeability curve, the flow characteristics of the reservoir, the results show that the flowing characteristics is significantly common oil-water relative permeability curves show slightly oil wet, the saturation of the irreducible water is low, oil permeability after-breakthrough decline faster and other characteristics.The combination of slit-like intergranular pore is the best type of reservoir for the study area, mainly refers to the pores of slit-like pore between the particles, the corroded pores, intercrystal pores, the remaining intergranular pores, micro-particles or cement joints and other pore combination. Such rock is generally loosely cemented, easily form slit-like intergranular pore in the development process.