缝洞型碳酸盐岩油藏非混相气驱采收率影响因素

Influence Factors of Immiscible Gas Flooding Recovery in Fractured-Vuggy Carbonate Reservoirs

为研究缝洞型碳酸盐岩油藏非混相气驱采收率的影响因素,建立了缝洞介质机理模型,分析了注采井所处的储集层类型、注采井间洞的分布、注采部位及注气速度等对非混相气驱采收率的影响。研究发现,非混相气驱的主要机理为油气密度差异形成的重力驱、膨胀原油增加弹性能量和降低原油黏度改善流动能力;气驱过程中宜选取缝注洞采,高部位注低部位采的注采方式;洞的存在有利于降低气窜风险,洞距离油藏顶部和生产井越近,采收率越高;采收率随注气速度的增加呈现先增大后减小的变化趋势。模拟结果表明,非混相气驱采收率主要受重力、储集层类型、注采井间洞的分布及注气参数的影响。

In order to study the influence factors of immiscible gas flooding oil recovery in fractured-vuggy reservoirs, the mechanism mod-els of fractured-vuggy media are developed to analyze the influence of injection and production wells＇ reservoir type, vug distribution be-tween injection well and production well, injection and production sites and gas injection rate on the EOR. The results show that the mainmechanism of immiscible gas flooding is gravity drive due to the density differences between oil and gas, oil expansion and oil viscosity re-duction to improve the flow ability. A better process could be gas injecting in fractured reservoir and high site, and oil producing in vuggyreservoir and low site. The existence of vugs could reduce the risk of gas channeling. The closer the vug to the top of reservoir and produc-tion well is, the higher the oil recovery will be. The oil recovery of gas flooding will increase and then decrease with the increase of gasflooding rate. The simulation results show that the oil recovery of gas flooding is mainly influenced by gravity, reservoir types, the distribu-tion of vug between injection well and production well and gas injection parameters.