微胶囊聚合物的时变特征及提高采收率机制

Time-varying characteristics and enhanced oil recovery mechanism of microencapsulated polymers

摘要

微胶囊聚合物通过缓释增黏抵抗炮眼剪切,提高聚合物驱效果。然而,微胶囊聚合物的时变特征导致其渗流行为和驱油机制与常规聚合物相差较大,提高采收率机制不明确。从形态和流变角度研究时变特征,并进行岩心驱替实验,利用CT扫描驱替实验研究动态剩余油动用机制。结果表明:微胶囊聚合物经历“溶胀颗粒-颗粒网络-高分子网络”的形态变化和“微弱黏弹膨胀性流体-低黏弹假塑性流体-高黏弹假塑性流体”的流变性变化,有利于前期注入、中期运移、后期波及;微胶囊聚合物适用于(300~500)×10^-3 μm²的渗透率范围和级差小于等于5的非均质条件,在增黏过程中表现出主流扩边式时变渗流特征,提高采收率幅度由4.32%增至19.29%;微胶囊聚合物增黏前推进至高渗岩心后端,增黏过程中逐渐波及低渗岩心,增黏后剩余油动用程度明显高于聚合物驱,证明可进一步大幅度提高采收率。

Abstract

Microencapsulated polymers can resist borehole shear by their slow-release and thickening effects, which can improve polymer flooding efficiency. However, the time-varying characteristics of the microencapsulated polymers can lead to significant differences in their flow behavior and oil recovery mechanisms compared to conventional polymers, and the mechanisms for enhancing oil recovery are not fully understood. In this study, the time-varying characteristics of microencapsulated polymers were studied in terms of morphology and rheological properties. The results show that microencapsulated polymers can undergo a morphological change from swelling particles-particle network to polymer network and a rheological change from weak viscous elastic expanding fluid to low viscous elastic pseudo-plastic fluid and to high viscous elastic pseudo-plastic fluid, which are beneficial for injection in the early stage, migration in the middle stage, and volume sweeping in the later stage of the polymer flooding process. The results of core displacement experiments show that microencapsulated polymers are suitable for the permeability range of (300-500)×10 ^-3 μm ² and heterogeneous conditions with a gradient of less than or equal to 5. During the thickening process, a kind of time-varying flow characteristics can appear via mainstream expansion, and the oil recovery rate was increased from 4.32% to 19.29%. Using CT scanning displacement experiments to study the dynamic residual oil utilization mechanism, the results show that the microencapsulated polymer can advance to the back of the high permeability core before thickening, and gradually spread to the low-permeability core during the thickening process. The degree of residual oil recovery after thickening is significantly higher than that of conventional polymer flooding, proving that it can further significantly improve the recovery rate.

关键词

微胶囊聚合物 / 缓释增黏 / 时变特征 / 渗流行为 / 驱油机制

Key words

microencapsulated polymer / slow-release and thickening / time-varying characteristics / flow behavior / oil displacement mechanism

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基金资助

国家油气重大专项(2025ZD1406100)