「Roweらの収れん圧力定義」の多成分型油層模型への応用に関する一提案

抄録

A vapor-liquid equilibrium calculation method fit for compositional reservoir models was presented. The compositional effects on the equilibrium ratios were taken into account by employing Rowe's definition of convergence pressure¹⁴⁾. The difficulty of insuring the smooth calculation when the fluid composition is close to a bubble point curve, a dew point curve, or a critical point, which is often the case when the convergence pressure is calculated iteratively, was resolved by defining the mole fraction of vapor phase V extendedly in (-∞, +∞) and equilibrium ratios in the pressure range greater or less than convergence pressure.
The method was tested in the reservoir simulation of pressure maintenance processes using three and seven component fluid systems, and smooth calculation was observed. In addition, the method was compared with one employing a fixed convergence pressure, and it was found that the former could predict reliable phase diagrams of the three component system but the latter could not, and that the recovery curves in the pressure maintenance process predicted by the both methods were unlike. These two facts indicate the preferability of employing varying convergence pressure in compositional models. An additional computer time to recalculate convergence pressure was observed to have been small compared with the total computer time required for the reservoir simulation.