针对目前大庆外围油田CO₂驱油区块采收率主要通过数值模拟方法进行预测、缺乏适合的经验公式等问题,建立了基于大庆外围油田基础物性和流体PVT参数的混相、近混相、非混相驱非均质理想模型,定义了含碳率-累产油、A型、B型三种CO₂驱特征曲线,利用特征曲线预测模型中的采收率,优选出适合CO₂近混相驱的特征曲线计算方法。在此基础上,建立了适合S区块的含碳率和采出程度图版,并与S区块实际动态相比较,选取A型气驱特征曲线进一步建立了CO₂近混相驱特征图版,应用改进后的图版预测了S区块CO₂驱采收率。结果表明:运用CO₂近混相驱特征图版预测的采收率与S区块现场预测的采收率比较接近,此方法可以简单快捷预测CO₂驱采收率,同时为S区块以及类似区块下一步的开发及评价提供参考。

At present, the oil recovery in the CO₂ oil displacement area of the peripheral oilfields in Daqing is mainly predicted by numerical simulation with no empirical formulas. In order to solve this problem, firstly, an heterogeneous ideal model of miscible, near-miscible and immiscible by CO₂ flooding based on the basic physical properties and PVT parameters of the peripheral oil field in Daqing oilfield is established. Secondly, three kinds of characteristic curves of CO₂ flooding are defined, including carbon content-accumulation of oil, type A and type B. The feature curve is used to predict the recovery rate in the model, and the calculation method of characteristic curve suitable for CO₂ near-miscible flooding modes is optimized. On this basis, the carbon content and recovery degree chart suitable for S block is established, and compared with the actual performance of S block. A-type gas drive characteristic curve is selected for the further establishment of the CO₂ near-miscible drive chart, and this improved chart is applied to predict the recovery rate of S block. The results show that the recovery rate predicted by the CO₂ near-miscible flooding chart is close to that predicted by the field test of S block. This method can predict the recovery rate of CO₂ flooding simply and quickly, and has guiding significance for the next development and evaluation of S block and similar blocks.