特低渗透高含水油藏CO_(2)驱油参数优化

Optimization of CO_(2) Flooding Parameters in Ultra-Low Permeability Oil Reservoirs with High Water Cut

为明确生产参数对特低渗透油藏高含水期CO_(2)驱油提高采收率的影响,进行了CO_(2)驱油数值模拟研究。通过CO_(2)连续注气驱参数优化发现:CO_(2)注入速度的提高会提高产油速度,但同时也会导致气窜的加剧和换油率的降低,并存在压裂地层的风险。生产井底流压的提高短期内会限制产油速度,但有利于提升地层压力水平,促进CO_(2)同地层油传质混相进而提高阶段采出程度和换油率。开发时在能够保证注采平衡的条件下,应尽可能提高井底流压。区块含水率的提高会使CO_(2)驱油效果变差,导致CO_(2)驱油阶段采出程度和换油率降低。CO_(2)驱油开发时换油率会随着生产气油比的提高而降低,因此,注CO_(2)开采过程应适时关井停注保证合理的CO_(2)注入量。优化得出CO_(2)注入速度15 000 m^(3)/d、生产井底流压25 MPa、CO_(2)注入时机为区块含水率60%时、关井时机为生产气油比达到1 000 m^(3)/m^(3)时、合理的CO_(2)注入量为9.2万吨。应用优化所得参数进行模拟预测结果表明:注CO_(2)开发9年后,区块原油产量相比水驱阶段增加了21.3万吨,采出程度提高了27.4%,阶段累计换油率0.58,累计埋存率0.67。

To investigate the interactions between CO_(2) and CH_(4) in aqueous phase and their competitive dissolution effects on CO_(2)-enhanced oil recovery processes,a numerical simulation model incorporating the competitive dissolution of CO_(2) and CH_(4) was developed.The established model modifies the solubility of CH_(4) at different CO_(2) concentrations and improves the equilibrium constants that characterize methane solubility.Simulation results indicate significant changes in the distribution of gas components due to competitive dissolution,affecting the gas-oil ratio and water cut fluctuations,thereby impacting the production performances of the reservoir.Under competitive dissolution,the CH_(4) content in the gas phase increases,further confirming the complexity of interactions between CH_(4) and CO_(2).This model accurately reflects gas interactions during the CO_(2) flooding process.