鄂尔多斯盆地红河油田长8储层致密砂岩油藏注CO2提高采收率

鄂尔多斯盆地红河油田地层压力系数低，天然能量开发递减较快、采收率低，难以实现有效开发。而长8储层裂缝较发育，注水补充能量开发存在油井水窜严重、见效低等问题。为了解决补充能量的问题，进行红河油田长8储层注CO₂提高采收率的可行性实验研究，室内开展了PVT实验、最小混相压力实验和裂缝岩心CO₂驱油实验，并评价了CO₂吞吐的开发效果。实验结果表明：红河油田原油注入CO₂后体积增大，具有较强的膨胀能力。而且随着混合体系压力逐渐增大，原油与CO₂能产生明显的相互扩散传质作用。长细管混相仪法测得红河油田原油与CO₂的混相压力为17.34 MPa，低于红河油田原始地层压力，注CO₂驱油能达到混相条件。通过多轮次CO₂吞吐实验，在弹性开发采收率4.04%的基础上可提高采收率3.14%。综合室内可行性评价实验结果看,红河油田长8储层注CO₂补充能量开发具有可行性。

CO2-EOR in Chang 8 tight sandstone reservoir of Honghe oilfield in Ordos Basin

The Honghe oilfield in Ordos Basin has difficulty achieving effective development due to low formation pressure, quick production decline and low recovery efficiency during natural depletion.In addition, natural fractures are well developed in Chang 8 tight sandstone reservoir, making it difficult to carry out waterflooding due to serious water channeling and low efficiency.Various CO₂-EOR experiments including PVT, minimum miscible pressure and CO₂ flooding in fractured cores were performed to determine the feasibility of maintaining reservoir pressure via CO₂ injection.The performance of CO₂ puff-huff was also eveluated.The results show that the crude oil of Honghe oilfield swells significantly after CO₂ injection.The diffusion between crude oil and CO₂ gradually increased as the pressure grows.The measured miscible pressure of crude oil and CO₂ is 17.34 MPa, lower than the initial formation pressure of Honghe oilfield, indicating that miscible flooding of CO₂ is feasible.Multi-cycle CO₂ huff-puff experiments show that an additional oil recovery factor of 3.14% can be achieved on the basis of 4.04% of natural depletion.A comprehensive evaluation of the experiment results indicates that CO₂ injection is feasible in Chang 8 reservoir of Honghe oilfield.