低渗透油藏CO2驱油数值模拟方法与应用

为弄清正理庄油田樊142块CO2驱油前缘特征和驱油效果,开展CO2驱油数值模拟方法和采油井开井顺序研究。利用多相渗流理论和数值求解技术,研制全隐式CO2驱油油藏数值模拟器。运用地质和生产资料分析和数值模拟相结合的手段,研究了压力恢复阶段连续注入CO2油层中CO2的分布和前缘推进情况。发现CO2前缘存在明显指进,注入2 a后,前缘已到达樊142-6-2井,前缘距樊142-6-3井和樊141-1-1井的最短距离分别为52和45 m。低压区的樊142-8-3和樊142-7-3井先开井,生产1 a后其余4口井再开井生产为最佳方案,该方案比同时开井累积生产5 a的采收率高1.34%,增产油量为5 407 t。通过采出程度、CO2埋存率和换油率对比可以看出开井顺序对驱油效果影响显著。

Numerical simulation method and application of CO2 flooding in low permeability reservoirs

In order to clarify the characteristics of front and displacement efficiency of CO2 flooding in Fan142 Block,Zhenglizhuang Oilfield,a numerical simulation method for CO2 flooding and the optimization for well open sequence for oil wells are studied. A fully-implicit reservoir numerical simulator for CO2 flooding is developed by using the multiphase percolation theory and the numerical solution technique. Combining the geological/production data analysis and oil reservoir simulation,the distribution of CO2 and the displacement front of the block are studied during the pressure build-up stage by continuous CO2 injection. It is found that an obvious fingering phenomenon occurs at the CO2 flooding front. After 2 years of injection,the front has reached Well F142-6-2. The shortest distances from the front to Well F142-6-3 and F141-1-1 are 52 m and 45 m,respectively. The best scheme is that wells F142-8-3 and F142-7-3 in the low pressure area are first opened and the remaining 4 wells are opened for production after 1 year. The cumulative production for 5 years of this scheme is 1.34% higher than that of the scheme that the wells are opened at the same time,and the increase of oil production is 5 407 t. By comparing the oil recoveries,geological sequestration rates and replacement rates of CO2,it is indicated that the sequence of well opening have an significant effect on the displacement efficiency.