Study on influencing factors and mechanism of pore compressibility of tight sandstone reservoir—A case study of upper carboniferous in ordos basin

A series of studies were carried out on 11 tight sandstone samples Upper Carboniferous in Ordos Basin. Firstly, the deposit composition and pore structure characteristics are investigated based analysis experiments including cast thin section scanning electron microscope high-pressure mercury intrusion nuclear magnetic resonance Then, combined with DP-P test, stress-dependent permeability change compressibility reservoirs studied to reveal influencing factors mechanism reservoir compressibility. The detrital particles study area mainly quartz (75.8%–89%), followed by fragments (3%–16.1%), almost no feldspar. content interstitial materials is 6.5%–11.2%. type I consist mesopores macropores, accounting for 60.57% 32.84% respectively. Mesopores dominated Type II reservoirs, 78.98% total volume. There while a similar proportion mesopores, micro micropores Ⅲ reservoirs. shows that coefficient decreases increase effective stress, reduction rate two-stage rapid early stage slow later stage. pressure turning point between 3 10 MPa. average increases from directly proportional changing higher rigid particles, carbonate cement sandstone, smaller coefficient, ductile components such as soft rock clay minerals, greater compression coefficient. pore-throat closely related compressibility, low displacement pressure, T 2glm value, large radius show lower In addition, positively correlated D L (dimension pores macropores), negatively S (the fractal dimension mesopores). It considered two stages, viscoplastic destructive deformation first then small-scale non-ideal elastic particles.