Abstract: The complex differential waveforms between geophysical logging curves conceal petroliferous information of reservoirs, which can be described by chaos dynamics system. And the chaos attractor is of low fractional dimension. The study shows that the phase space attractor of pay zone is characterized by self-scaling structure and relatively high dimension and fast convergence of correlation dimension spectrum; the phase space attractor of water-flooded zone or water layer is of clearly weakening chaos characteristic and simple/in-order system with low dimension and slow convergence of correlation dimension spectrum. The signal chaos dynamics characteristic only depends on the signal complexity level and is independent of the signal absolute value. It is concluded that the method for well logs-based chaos fractal characteristic to identify water-flooded zone can be well applied to distinguish low-resistivity pay zone and high- resistivity water-flooded zone or water layer that are badly identified by using conventional well log interpretation theory.

Key words: water flooded zone, well log curve, chaos, fractal, identification