| Lattice Boltzmann method(LBM)and color gradient model were used to study the displacement patterns and displacement efficiency of two immiscible two-phase flow in two-dimensional porous media.As important parameters to describe displacement,the capillary number Ca was set as 0.01,1,100,viscosity ratio M was set as 0.1,1,10,and wettability was characterized by contact angle ,which traversed from 0 to 180 at intervals of 10.A total of 171 groups of simulations were conducted to obtain the displacement morphology of different wettability under different capillary numbers and viscosity ratios.In order to describe the influence of wettability on displacement efficiency,a relative saturation was defined.The results showed that when the invading fluid was wetting,namely < 90,almost no defending fluid remained in the pore and the displacement efficiency was very high.When the invading fluid was non-wetting,namely > 90,there were much defending fluid pinned to the solid boundary and the displacement efficiency was low.The displacement efficiency was not always the highest at the contact angle of 0-10,but sometimes there was a saturation maximum in the range of 20-70.In stable displacement,the curves of saturation with contact angles showed a bi-linear trend at 0-90 and 90-180,respectively.The expression can be obtained by fitting.Based on the simulation results,the M-Ca- three-dimensional phase diagram was proposed on the basis of the traditional M-Ca phase diagram,which explained the moving characteristics of the M-Ca phase diagram.When hypergravity was taken into account,the amount of fingers increased and its width decreased,and the mixing of the two-phase fluid was more fragmented. |
