摘要：Because of a high mobility ratio in the chemical and gas flooding for oil reservoirs, the problems
of numerical dispersion and low calculation efficiency also exist in the common methods, such as
IMPES and adaptive implicit methods. Therefore, the original calculation process, “one-step
calculation for pressure and multistep calculation for saturation,” was improved by introducing a
velocity item and using the fractional flow in a direction to calculate the saturation. Based on these
developments, a new algorithm of numerical solution for “one-step calculation for pressure,
one-step calculation for velocity, and multi-step calculation for fractional flow and saturation” was
obtained, and the convergence condition for the calculation of saturation was also proposed. The
simulation result of a typical theoretical model shows that the nonconvergence occurred for about
6,000 times in the conventional algorithm of IMPES, and a high fluctuation was observed in the
calculation steps. However, the calculation step of the fast algorithm was stabilized for 0.5 d,
indicating that the fast algorithm can avoid the nonconvergence caused by the saturation that was
directly calculated by pressure. This has an important reference value in the numerical simulations
of chemical and gas flooding for oil reservoirs.
