Percolation in two-scale porous media

Two-scale porous media are generated by filtering a Gaussian random correla ted field with a random correlated threshold field. The percolation thresho ld and the critical exponent nu are derived with the help of a finite-size scaling method. The percolation threshold for the three-dimensional media i s a decreasing function of the variance and correlation length of the thres hold field. A simplified model predicts these trends in 3d; moreover, it su ggested some effects in 2d which were all numerically verified.