考虑高速非达西效应的油水相对渗透率计算模型

油水相对渗透率是描述储层多孔介质油水渗流的重要参数,高产的高孔高渗油藏在近井地带可能会发生单相或两相的非达西渗流,以致于在常规条件下得出的相渗曲线并不能准确地表达该类油藏的渗流特征,导致产能评价及预测不合理。通过考虑高孔高渗储层多孔介质的油水渗流特征,建立了考虑高速非达西效应的高孔高渗油藏非稳态油水相对渗透率计算模型,进行了非稳态油水相对渗透率实验,计算了不同油相或水相非达西系数对油水相对渗透率曲线的影响,最后数模分析了高速非达西效应对高孔高渗油藏的影响。研究表明,水相对油水相对渗透率曲线的影响较为显著,非达西效应的影响在油水相渗曲线的两端更为明显。两相高速非达西效应虽然降低了油藏的总体产液量,但是抑制了产水,增加了产油量,与单相高速非达西效应相比,两相高速非达西效应对油田生产并不一定具有负面作用。

Calculation model for oil-water relative permeability considering non-Darcy effect

Oil-water relative permeability is an important parameter to describe the fluid flow in porous media of reservoir. Since single phase or two-phase non-Darcy flow may occur in the near wellbore region in high porosity and permeability reservoirs, the conventional relative permeability for Darcy flow may not be able to accurately describe the fluid flow characteristics, which results in unreasonable well performance prediction and evaluation. Based on the characteristics of oil and water flow in porous media of high porosity and permeability reservoir, an oil-water relative permeability model has been established considering the non-Darcy flow effect in high porosity and permeability oil reservoirs. The experiment of unsteady oil-water permeability is done and the influence of different oil phase and water phase non-Darcy coefficient on oil-water relative permeability curve is calculated. Finally, the non-Darcy effect on reservoir performance was analyzed by numerical simulation. The results show that water inertia coefficient has more influence on the relative permeability curves and non-Darcy effect is more significant at endpoint of the relative permeability curves. The two-phase non-Darcy effect reduces the total liquid production and the water production from the oil reservoir, so the oil production may increase. Hence, comparing with single-phase flow, two-phase non-Darcy flow may not always have negative effect on the oil production of high porosity and permeability oil reservoirs.