Abstract: W2 fault block has low to ultra low permeability reservoir with poor poroperm characteristics, complex pore structure and relatively strong heterogeneity. Meanwhile, percolation pattern of fluids gets more and more complex during waterflooding, due to the influences of microfis-sures. In order to better understand the status of water-flooding, the vertical and horizontal reservoir heterogeneities and remaining oil distributions in this oil reservoir, microelement interwell tracing has been performed in one well selected in this block. It reveals, to some extent, the distribution patterns and characteristics of the static and dynamic parameters of well groups, which provide a direct basis for improving waterflooding effects.