Abstract
<title>Abstract</title> <p>To figure out the distribution and influencing factors of movable fluids in ultra-low permeability sandstone reservoirs, this research takes Chang 6 member in the Wuqi area as an example. Through a series of experiments, the occurring and influencing factors of the movable fluid were analyzed. The results show that the ultra-low permeability sandstone reservoirs in this research have porosity values ranging from 8.78% to 16.12%, permeability values ranging from 0.094mD to 1.467mD, and the values of movable fluid saturation ranging from 31.38% to 62.67%. All the samples can be comprehensively divided into two types, type I samples have higher content of feldspar, more developed dissolved pores, and generally locate in middle part or top part of thicker sand bodies. For all the samples, the movable fluid saturation, permeability, rpeak, and r50 have a strong correlation with each other, which may be associated with the development of large pore-throats. Although the movable fluid occurs in pore-throat with a wide size range, the development of micron pore-throats is the key influence on the values of movable fluid saturation, differentiating ultra-low permeability reservoirs and tight sandstone reservoirs.</p>