苏北盆地注CO2提高采收率技术面临的挑战与对策

Challenges and countermeasures of EOR by CO2 injection in North Jiangsu Basin

苏北盆地注CO2提高采收率技术历经4个发展阶段,在目前低油价下,主要面临注CO2驱成本高难以实现效益开发,最小混相压力高难以大幅度提高采收率以及非均质性较强难以扩大CO2驱波及体积三方面的挑战。主要对策:一是以优化方案为关键,充分利用老井,减少新井投入,优化注入方式,减少注气用量,利用已有设备,减少地面及回收投资,整体规划管网,降低气价成本等方法降低CO2驱油成本,将60%的CO2驱油项目平衡油价控制在60美元/bbl以下;二是开展降低最小混相压力添加剂的筛选评价,并通过先期注入等方式提高地层压力,改善混相条件,提高CO2驱油采收率;三是利用高部注入、水气交替、调整剖面等手段减缓气窜,提高CO2驱波及体积。通过研究和实践,为低油价下类似油藏的CO2驱油效益开发提供了参考和借鉴。

CO2 injection for enhanced oil recovery(EOR)has gone though 4 stages of technical improvements in North Jiangsu Basin.During the current low oil price period,three challenges are exiting:the high cost of CO2 flooding makes it difficult to realize benefit development,the minimum miscible pressure(MMP)is too high to enhance oil recovery substantially,and the heterogeneity is too strong for expanding CO2 swept volume.Therefore,three main countermeasures is put forward.Firstly,the optimization of scheme is the key.By full advantage of the old wells to reduce investment for new wells,optimization of injection mode to reduce injection volume,use of current equipment to reduce recycling cost,and overall plan for the pipe network to reduce gas cost,the cost of CO2 flooding is reduced,thus,the equilibrium oil price of 60%of the CO2 flooding project will be kept below$60/bbl.Secondly,screening and evaluation of additives to reduce MMP are carried out.Meanwhile,the miscible condition was improved and the recovery rate of CO2 flooding was increased by the injection in advance to increase the formation pressure.Tiredly,the swept volume of CO2 is improved by means of injection at the high parts,water alternating gas injection(WAG),and profile modification to mitigate gas channeling.The research and practice offer reference and examples for the beneficial development of CO2 flooding in similar reservoirs under low oil price.