考虑封存机理的低渗透油藏CO_(2)驱油与封存注采参数敏感性分析

Sensitivity Analysis on Injection⁃Production Parameters for CO_(2)EOR and Storage in Low⁃Permeability Reservoirs Considering Storage Mechanism

低渗透油藏采用CO_(2)驱油,既可以提高油气采收率,又能实现CO_(2)地质封存。基于CO_(2)封存机理,采用数值模拟方法,建立了考虑CO_(2)构造封存、束缚封存和溶解封存的驱油与封存机理模型,研究在连续注气开发和水气交替注入开发下,不同注采参数(注水年限、CO_(2)注入速度、注采比、生产井井底流压下限、注入井井底流压上限、循环次数和气水段塞比)对低渗透油藏CO_(2)驱油采收率与CO_(2)封存效率的敏感性。结果表明:CO_(2)封存机理会对CO_(2)驱油以及CO_(2)封存造成很大的影响。连续注气开发时,CO_(2)束缚封存有利于驱油,但对CO_(2)封存影响不大;CO_(2)溶解封存不利于CO_(2)驱油,但是有利于CO_(2)封存。水气交替注入开发时,CO_(2)封存机理不利于CO_(2)驱油,但是对CO_(2)封存有促进作用。研究结果可揭示不同CO_(2)注入方式下,封存机理对驱油与封存的影响规律。

In low⁃permeability reservoirs,CO_(2)flooding can enhance oil recovery and achieve CO_(2)geological storage.Based on the CO_(2)storage mechanisms,by using a numerical simulation method,a CO_(2)EOR and storage model considering CO_(2)structural storage,residual storage,and dissolution storage mechanisms was established.This model was used to analyze the sensitivity of injection⁃production parameters(e.g.water injection period,CO_(2)injection rate,injection⁃production ratio,lower limit of bottomhole flowing pressure in production wells,upper limit of bottomhole flowing pressure in injection wells,number of cycles,and gas⁃to⁃water slug ratio)on CO_(2)EOR and CO_(2)storage efficiency in low⁃permeability reservoirs under continuous gas injection and water⁃alternating⁃gas(WAG)injection modes.The results demon⁃strate that CO_(2)storage mechanisms have significant impacts on both CO_(2)EOR and CO_(2)storage.Under the mode of continuous gas injection,CO_(2)residual storage aids CO_(2)EOR but has minimal effect on CO_(2)storage,while dissolution storage hinders CO_(2)EOR but benefits CO_(2)storage.Under the mode of WAG injection,the storage mechanisms are less favorable for CO_(2)EOR but promote CO_(2)storage.These findings reveal the influences of storage mechanisms on CO_(2)EOR and storage under different injection modes.