Movable Fluid Distribution Characteristics and Microscopic Mechanism of Tight Reservoir in Yanchang Formation, Ordos Basin

Tight sandstone reservoirs have smaller pore throats, complex structures, strong heterogeneity in the throat system, and significant differences fluid distribution. To reveal occurrence characteristics of movable fluids tight reservoirs, typical core samples from Chang 4+5 reservoir Upper Triassic Yanchang Formation Ordos Basin were selected micro classification standard was established by using casting thin slices, field emission scanning electron microscopy (FE-SEM), high-pressure mercury injection (HPMI), nuclear magnetic resonance (NMR) technology. The test analysis results showed that can be divided into Type I, II, III different structure. I well-developed good connectivity, low threshold pressure (0.42 MPa on average), high saturation (46.82% a minimum radius (0.056 ?m average). structure production degree other two types gradually deteriorated. Note throats but content (17% With deterioration reservoir, utilization larger decreases (74.33%–57.33%), whereas does not change significantly (25.67%–13.82%). Many factors affect parameters. parameters positive correlation with permeability ( R 2 = 0.85) sorting coefficients 0.88). no obvious single factor. Multiple scale throats.