Characterization of oil-water two phase flow patterns in vertical upward flow pipes is studied based on fractal and chaotic time series analysis of conductance fluctuation signals. For 60.5%≤ K w≤91% and 10 m 3· d -1 ≤ Q t≤60 m 3·d -1

local fractal dimension and correlation dimension of chaotic attractors are in the range from 1.006 to 1.631 and from 4.30 to 6.77

respectively. For K w=51% or K w=51.5% and 20 m 3·d -1 ≤ Q t≤60 m 3·d -1

fractal dimension and correlation dimension of chaotic attractors are in the range from 1.17 to 1.758 and from 5.46 to 7.05

respectively. Both dimensions show an irregular sudden change with variation of total flowrate Q t

which corresponds to happenings of transitional flow pattern. The irregular sudden changes in dimensions are verified with complex power spectrum and flow pattern map proposed by our previous study. It is shown that fractal dimension and correlation dimension of chaotic attractors is sensitive to flow pattern variation as an "indicator".