Movable fluid distribution and controlling factors in upper paleozoic tight sandstone reservoirs: insights from the Shenmu Mizhi area

The physical properties of dense sandstone reservoirs are closely related to fluid flow. In this paper, we first analyze the effects of compaction and dissolution, cementation, accounting, and dissolution on diagenesis, and elucidate the effects of intra- and interlayer inhomogeneities on pore structure. Second, the gas-water flow characteristics under different reservoir types were analyzed, and the evaluation criteria of movable fluid saturation were formulated by using nuclear magnetic resonance (NMR) technology. Third, the influence of geological factors such as depositional and diagenetic environments on the permeability characteristics of reservoirs was explored. The results show that: (a) the interlayer nonhomogeneity is strongest in the former section 5 and river section 8, as well as in the Taiyuan and Benxi formations. (b) Bound water saturation in the study area ranges from 29.73 to 54.02%, with an average of 30.648%. (c) Type I macroporosity is developed, and most movable fluids are distributed in the macroporosity.