With the tight sandstone gas exploration and
development, to study the influencing factors of tight sandstone irreducible
water saturationbecomesimportant, as it can effectively guide reservoir
description, evaluation, and productivity prediction. As an example of the
tight sandstone reservoir in Linxing area in Ordos basin, the influencing
factors of irreducible water saturation in tight sandstone were analyzed by casting
thin section, X-ray diffraction, nuclear magnetic resonance, high pressure
mercury injection, gas-water phase permeability, and scanning electron
microscope experiments.The results show that the irreducible water saturation
of tight sandstone in the study area is 34.77% - 83.78%, withanaverage of 63.86%,
and the T2cutoff is 3.86 -
65.60 ms withan average of 20.96 ms.The irreducible water saturation of tight sandstone is
affected by physical properties, wettability, sensitivity, clay mineral type, mass
fraction, and particle size in reservoirs. The smaller the tight sandstone size
is, the higher the clay minerals content, and the stronger the rock
hydrophilicity; The greaterthe specific surface area and water film thickness
of the rock, the higher the capillary and membrane irreducible water. Water
sensitivity and salt sensitivity are the main factors causing the damage of permeability.
Residual intergranular pores, dissolution intergranular pores, dissolution
within grains, intercrystalline pores and micro-fractures are developed in the research
area. The types and forms of clay minerals filled in the pores are different,
resulting in the complex pore structure of tight sandstone, strong
micro-heterogeneity, and largeirregular changes in water saturation.