低渗透油藏毛细管压力动态效应

通过实验测定和数值模拟研究,分析低渗透油藏油水两相渗流毛细管压力动态效应,以明确其对水驱油特征的影响规律。建立了动态毛细管压力测量实验装置,对动态毛细管压力和含水饱和度变化率之间的关系进行了测定,并求得低渗透岩心的毛细管动态系数。基于测定结果建立了一维水驱油渗流数学模型,并用其研究了注水过程中动态毛细管压力对低渗透油藏水驱油渗流规律的影响。结果表明,低渗透油藏毛细管压力的动态效应非常显著,不能忽略;动态毛细管压力和湿相饱和度变化率之间近似为线性关系,且不同渗透率岩心的毛细管动态系数大小不尽相同,岩心渗透率越低,毛细管动态系数值越大,毛细管动态效应越明显,启动压力梯度越大。认为毛细管压力动态效应是造成低渗透油藏油水两相流动符合非达西渗流规律的原因之一,会对水驱油前缘的推进速度、沿程压力分布、见水时间、产油量、采出程度等开发指标产生影响。

Dynamic effect of capillary pressure in low permeability reservoirs

The dynamic effect of capillary pressure in oil-water two-phase percolation flow in low permeability reservoirs was investigated by experiment and numerical simulation. An experimental apparatus was constructed to measure the relationship between the dynamic capillary pressure and water saturation change rate, and the dynamic capillary coefficient of low-permeability cores was calculated. A one-dimensional mathematical percolation model was established to analyze the effect of dynamic capillary pressure on waterflooding process. The dynamic capillary pressure effect is too significant to be neglected. The relationship between the dynamic capillary pressure and the change rate of wetting phase saturation is almost linear. The lower the rock permeability is, the greater the dynamic capillary coefficient and threshold pressure gradient are. One of the reasons for non-Darcy two-phase percolation flow is the dynamic capillary pressure effect. The dynamic capillary pressure in low permeability reservoirs has a significant influence on development indices such as the velocity of displacement front, water breakthrough time, pressure distribution, oil production rate, and recovery degree.