Abstract:

On the basis of the porous flow mechanics and the non-Darcy motion equation in consideration of the threshold pressure gradient, a mathematical model of non-Darcy flow in low or ultra-low permeability reservoirs was established to reveal the characteristics of pressure distribution. The analytical solution was derived from the integral transformation after simplifying. A calculation method for reasonable control radius of individual unfractured well was presented. A log-log plate between matrix control radius and threshold pressure gradient was given under different pressure drawdown. On the basis of the elliptic flow theory, a new method for calculating the control coefficients of various well patterns was presented and used to quantitatively analyze the startup degree of reserves in different fractured well patterns. This method can provide the theoretical foundation for reservoir evaluation and development design of low or ultra-low permeability reservoirs.

Key words: low-permeability reservoir, non-Darcy flow；control radius；pressure distribution；threshold pressure gradient；fractured well pattern, mathematic model

摘要：

依据渗流力学基础理论，及考虑启动压力梯度存在的非达西运动方程，建立了低/特低渗透油藏流体非达西流动的数学模型。通过积分变换得出解析解，建立了单井未压裂情况下的合理动用半径的计算方法，并绘制了不同生产压差下的基质动用半径与启动压力梯度的双对数关系图版。结合压裂椭圆渗流理论，给出了不同面积井网压裂情况下动用系数的计算方法，用于定量表征不同井网条件下储层的动用程度，为低渗透储层的油藏评价和开发设计提供了理论依据。

关键词: 低渗透油藏, 储层非达西渗流, 动用半径, 压力分布, 启动压力梯度, 压裂井网, 数学模型