Influence of different pore structure types on the occurrence features of movable fluid in Chang-10 reservoir in Wuqi–Ansai Oilfield

Abstract Chang-10 reservoir in Wuqi–Ansai oilfield of Ordos Basin is restricted by its strong microscopic heterogeneity, complicated microscopic pore structure and unclear oil–water movement rules. The technology of nuclear magnetic resonance (NMR) is an excellent method to quantitatively evaluate the reservoir fluid of different pore structure types, and the microscopic experiments such as cast thin slices, scanning electron microscope (SEM) and high-pressure mercury injection were also used to analyze the differences in the occurrence features of fluid of different pore structure types and their influencing factors. The experimental results show that the sandstone types of Chang-10 reservoir in Wuqi–Ansai Oilfield are mainly medium-fine arkose and lithic arkose. The pore types are mainly intergranular pore, feldspar pore, turbiditic zeolite pore and cuttings pore. The combination type of pore-throat belongs to mesopore–micropore and microlarynx–microlarynx. By mercury injection experiment analyzed the characteristic of capillary pressure curve, Chang-10 reservoir in Wuqi–Ansai Oilfield pore structures is classified into Type I, Type II, Type III and Type IV due to the different movable fluid occurrence features. The occurrence features of movable fluid are obviously controlled by the pore-throat, and the orders of control effect from strong to weak are from Type I, Type II, Type III to IV The saturation of movable fluid gradually becomes low when the pore-throat radius decreases.