低渗油藏注水井达西-非达西耦合试井模型及压力分析

Darcy & Non-Darcy Coupled Flow Model and Its Pressure Analysis in Injection Well of Low-Permeability Reservoirs

低渗油田注水开发过程中,注水井周围的渗流特征明显不同。考虑注水井附近内区为水相达西渗流,外区为油相非达西流动,建立了变渗透率效应下的达西-非达西非耦合渗流试井模型,采用交替迭代法对非线性差分方程组迭代求解。计算结果表明,外区油相非达西流动,在试井曲线上显示压力导数上翘,注水井油水交界处越近,压力导数曲线与压力曲线重合时间越长,近井地带憋压现象越严重。基于变渗透率效应建立的达西-非达西耦合渗流试井模型及其解符合实际低渗油田注水开发情况。实际低渗油藏注水井试井分析实例说明,新模型解释结果符合实际地层流动条件,结果正确。

In the water-flooding development of low permeability reservoirs,the percolation characteristics of near the injection well are completely unlike.Considering that the zone near the well is water phase of Darcy flow,the outer is oil phase of non-Darcy flow,Darcy & nonDarcy coupling flow model has been established,and the iterative algorithm is adopted to solve the non-linear differential set of equations.Calculated results show that the up-warding in the derivative pressure curve is caused by the non-Darcy flow at outer zone,and the closer the contact of water-oil is,the longer the superposition time of the pressure & derivative pressure curve is,and the severer the phenomenon of pressure builds up.The new Darcy & non-Darcy coupled flow model and its solution based on changing permeability effect fit better in real condition of low-permeability reservoirs which are developed by the water-flooding program.The actual well testing analysis examples in low permeable oil reservoirs of injection well indicate that interpretation results from the new model accords with the actual formation flow condition,and the result is correct.