关键词: 粘性指进, 分形集团, 分数维, 粘度比, 驱扫效率

Abstract: The morphological evolution characteristics of viscous fingering, which occurred in two-dimension Hell-Shaw cells with the viscosity ratio V_R between the displaced and the driving fluids varying from 1 to 10000, were simulated by a modified DLA model on off-lattices, which was some different from the conventional method and the effect of surface tension was also taken into account.Both the shapes of fractal clusters and the fractal dimension obtained by controlling the parameters in the present model are in good agreement with the experiments.The present work indicates that the fractal dimension D and the viscosity ratio V_R follows the formula D=2.0384-0.0384V_R^1/3.The sweep efficiency is proportional to the logarithm of V_R, E_S=1-0.1795log (V_R).So, the greater the value of V_R, the less the fractal dimension D and the lower the sweep efficiency E_S.Thus, the parameters such as fractal dimension D, which describes the complexity in a system, viscosity ratio V_R, which influences the dynamics of fingering, and sweep efficiency E_S, which scales the EOR programs, were connected by the present study.The fractal dimension can be reasonably regarded as a useful parameter to evaluate the sweep efficiencies and oil recoveries.The present results suggest that the improvement in sweep efficiencies for EOR programs may be achieved by the means of increase in fractal dimension of viscous fingering.

Key words: viscous fingering, fractal clusters, fractal dimension, viscosity ratio, sweep efficiency