Network modelling of gas relative permeability in heavy oil.

摘要

Some of the solution gas drive heavy oil reservoirs (foamy oil reservoirs) in Canada, Venezuela, China, and Oman have experienced unusual high primary oil recovery factor (>10%), low producing gas oil ratio, low reservoir pressure decline, and high oil production rate. One of the hypotheses to explain the behaviour is that the gas mobility in foamy oil flow is much lower than that in conventional oil, leading to improved recovery performance. In this study, immiscible micro-displacement in porous media was modeled by using a network of pores of converging-diverging geometry. The effect of viscosity of one phase (oil) on the mobility of another phase (gas) is included in the model. The developed model is used to simulate the motion of the dispersed gas bubbles in an initially oil filled network, and to determine gas relative permeability. The obtained results showed that gas relative permeability decreased drastically by increasing the oil viscosity. In addition, it is shown that dispersion of gas leads to lower relative permeability to gas. Dispersed gas flow and low gas mobility are believed to lead to improved recovery in foamy oil reservoirs.