特低渗透油藏面积井网见水时间计算

特低渗透油藏在水驱开发过程中常表现出渗透率各向异性和流体非达西渗流特征,运用非达西渗流公式及流线积分法,得到特低渗透油藏五点井网、反九点井网和菱形反九点井网在油水两相非活塞式驱替条件下的油井见水时间.计算长庆鄂尔多斯盆地某特低渗透油藏井网见水时间,结果与实际动态符合较好.分析油水黏度比、渗透率各向异性及启动压力梯度对油井见水时间的影响,结果表明:油水黏度比越大,油井的见水时间越早;当菱形反九点井网长轴方向井距与短轴方向井距之比与渗透率各向异性强度大致相等时,长轴方向与短轴方向上的角井能实现均衡驱替;启动压力梯度延缓了油井的见水时间,且生产井距越大,启动压力梯度的影响越显著.

Calculation of Water Breakthrough Time in Well Patterns of Ultra-low Permeability Reservoir

As ultra?low permeability reservoir is developed by water flooding, it always presents characteristics of non?Darcy flow and permeability anisotropy. We derived water breakthrough time formula of five?spot well pattern, inverted nine?spot well pattern and rhombic nine?spot well pattern with basic non?Darcy flow formula and streamline integral method. Breakthrough time of one actual well pattern in Ordos Basin was calculated. Calculation results accorded with production data well. Effects of threshold pressure gradient, permeability anisotropy and viscosity difference between oil and water were analyzed. It shows that the greater the viscosity ratio of oil and water, the earlier the water breakthrough time; Corner well of rhombic nine?spot well pattern can realize uniform displacement both in x direction and y direction as ratio of well spacing in x direction and y direction equals to permeability anisotropy degree; The grenter the threshold pressure gradient, the latter the water breakthrough time. Effect of threshold pressure gradient became more apparent as well spacing is larger.