低渗油藏压裂直井最小流压界限求解及应用

Solution and Application of Minimum Threshold Flowing Pressure of Fracturing Vertical Well in Low Permeability Reservoir

低渗透油藏开发的显著特点是存在启动压力梯度和应力敏感现象,这种特有的现象使该类油藏与常规油藏的生产特征存在较大差异,常规方法不再适合计算其产能。基于扰动椭圆概念和等价发展矩形的思想,考虑原油脱气对油相流动能力的影响,引入油相、液相相对流动能力的概念,建立了同时考虑启动压力梯度和应力敏感的低渗透油藏压裂直井产能公式和流入动态方程,利用作图法绘制了求解最小流压界限的流入动态曲线图版,并应用于实际油藏进行了验证。结果表明,计算值与实测值具有很好的吻合度,从而证明了所提出的求解最小流压界限方法可以满足工程应用要求,能为现场制定合理的油井工作制度提供理论指导。

The development of low permeability reservoir is different with that of conventional reservoirs due to its threshold pressure gradient and stress sensitivity,therefore using conventional methods to study low permeability reservoir is inappropriate.Based on the idea of disturbed ellipse and equivalent developing rectangle,the concept of relative flow capacity in oil phase and liquid phase is introduced,considering the effect of degassing crude oil.Productivity equation and inflow performance equation for fractured vertical well were established considering the impact of threshold pressure gradient and stress sensitivity on low permeability reservoir.The IPR curve is plotted to solve minimum threshold flowing pressure which is verified using field data.The results indicate that calculated value agrees with the measured value.This method meets the practical requirements and provides theoretical guidance on optimization of development in field.