CO2地质封存过程中盖层和裂缝的自封闭机制研究现状

Research status of self-sealing mechanisms of caprocks and fractures during CO2 geological storage

  • 摘要: 通过对现有文献的系统调研,总结了CO2地质封存过程中物质重新平衡对盖层和裂缝自封闭规律的动态影响研究现状。室内实验、井场监测和数值模拟研究普遍显示,CO2注入后在短期内不会突破较厚的盖层,即使突破直接上覆盖层,也会被多层盖层系统二次捕获封存。盖层自封闭的机制主要包括超临界相态CO2注入限域空间导致的自封闭、岩石孔隙结构压缩,或微粒运移导致的机械作用自封闭和化学作用引起的自封闭。而裂缝或断层系统在CO2注入后的流体—岩石相互作用机制下,会随着时间推移倾向于逐渐形成自封闭,低CO2流速、小裂缝开度是形成裂缝/断层自封闭的主要因素。但在时间尺度的效应下,CO2的物理扩散、化学反应对盖层和裂缝的动态定量影响,仍然需要进一步详细研究。目前国内外对这一动态过程的研究正逐渐向多时空尺度协同、多研究手段结合、多因素耦合的系统过程发展,并且逐渐成为CO2地质封存研究的热点问题。

     

    Abstract: Through a systematic review of the existing literature, the current research on the dynamic effects of material re-equilibration on caprock and fracture self-sealing patterns during CO2 geological storage is summarized. Laboratory experiments, field monitoring at well sites, and numerical simulation studies generally show that CO2 injection will not breach relatively thick caprocks in the short term, and even if the directly overlying caprock is breached, CO2 will be secondarily trapped and sealed by multi-layered caprock systems. The mechanisms of caprock self-sealing mainly include self-sealing due to injection of supercritical-phase CO2 into confined spaces, mechanical self-sealing resulting from rock pore structure compression or particle migration, and self-sealing induced by chemical reactions. Under the fluid and rock interaction mechanisms after CO2 injection, fractured or faulted systems tend to progressively develop self-sealing over time. Low CO2 flow rates and small fracture apertures are identified as the main factors in the formation of fracture/ fault self-sealing. However, the dynamic quantitative effects of CO2 physical diffusion and chemical reactions on caprocks and fractures under time-scale effects still require further detailed investigation. Currently, research on this dynamic process at home and abroad is gradually evolving toward a systematic approach that integrates multi-spatiotemporal scale coordination, multiple research methods, and multi-factor coupling, and it is increasingly becoming a hot topic in research on CO2 geological storage.

     

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