深层砂砾岩油藏注CO2相态变化与吞吐参数优化

Phase behavior and parameters optimization of CO2 huff and puff in deep glutenite reservoir

WQN深层砂砾岩油藏存在自然产能低,压裂后稳产期短且产量递减快,注水开发效果差,地层能量亏空大,采出程度低等问题,目前油井多处于低速低效衰竭式开采甚至关停状态。开展了CO2驱室内实验研究和可行性分析。研究表明:注入CO2后能起到增溶膨胀,降黏改善流度比,补充返排所需能量等作用。运用CMG数值模拟技术对注入量、注入速度、焖井时间、返排速度、第二轮注气时机、吞吐周期等工艺参数进行优化。经矿场初步试验,W31井CO2注入量800 t,目前累计增油629.1 t,换油率已达0.79,初步取得了增油效果,为有效挖掘深层砂砾岩油藏剩余油提供了技术支持。

WQN deep glutenite reservoirs have problems such as low natural productivity,short stable production period after fracturing and rapid production decline,poor water injection development effect,large formation energy deficit,and low recovery.At present,the oil wells are mostly in a state of low-speed and low-efficiency depletion production or even shut down.Therefore,CO2 flooding experimental study and feasibility analysis have been carried out to improve the development effect.The research results show that the injection of CO2 can play a role in solubilizing and swelling,reducing viscosity,improving fluidity ratio,and supplementing the energy required for flowback.The CMG numerical simulation is used to optimize the process parameters such as injection volume,injection speed,soak time,flowback speed,gas injection timing for second round,cycle time of huff and puff,and so on.Preliminary pilot tests show that the CO2 injection volume of Well W31 is 800 t,the current cumulative oil increase is 629.1 t,the oil exchange rate is reached 0.79,and the oil increase effect has been achieved,which can provide technical support for the effective exploration of remaining oil in deep glutenite reservoirs.