特低渗油藏油气两相启动压力梯度研究

目前,国内外对启动压力梯度的研究主要集中在油水两相中,对于油气两相启动压力梯度研究很少.用特低渗透油藏的天然岩心,通过实验研究了不同流体,不同介质及不同注气条件下气驱油启动压力及其变化规律.研究结果表明:油气两相启动压力梯度随渗透率的增加而降低,与流体的流度呈半对数直线关系;随含油饱和度的降低而增加;有效应力对启动压力梯度影响很大;启动压力梯度随着回压的增加而降低,但幅度不大.

Study on Starting Pressure Gradient of Oil and Gas Two-phase Flow in Extra Low Permeability Reservoir

At present, the studies of starting pressure gradient in home and abroad are main focus on single phase and water-oil two-phase and there are a few studies of gas-oil two-phase. A serial of starting pressure gradient experiments of gas-oil two-phase were conducted on extra low permeability natural cores and the laws under different fluids, different porous medium and different operating conditions were studied at length. The results show that the starting pressure gradient decreases along with the increment of permeability and there is a semi-logarithmic relationship between it and mobility. The starting pressure gradient increases with the decrement of oil saturation; the effective stress has a strong effect on it; and it decreases with the increment of back pressure, but the decrease extend is limited.