工程科学学报2025，Vol.47Issue(5)：1117-1127,11.DOI:10.13374/j.issn2095-9389.2024.08.13.002
裂缝对咸水层内CO2对流混合特性的影响
Impact of fractures on convective-mixing characteristics of carbon dioxide in saline aquifers
摘要
Abstract
Fractures serve as the main channels for rapid CO2 diffusion and escape during sequestration in saline aquifers.While existing studies have focused on how fracture characteristics and chemical reactions affect CO2 convective mixing,the specific mechanisms at each stage of CO2 dissolution and sequestration are still not well understood.It is crucial to gain a deeper understanding of the overall impact of fractures on CO2 transport and sequestration.This paper presents a new coupling simulation model for CO2 convective-diffusion transport in fractured saline aquifers,developed using COMSOL Multiphysics 6.0.The numerical simulation analyzes how CO2 convection-diffusion in fractured saline aquifers,focusing on the effects of fracture width,inclination angle,and combination characteristics on CO2 convection and diffusion.It also examines CO2 behavior in large-scale fractured saline aquifers with a discrete fracture network.The results show that fractures located in the middle of saline aquifers have a dual,time-dependent effect on CO2 dissolution and diffusion,which becomes more pronounced as fracture width increases.Initially,these fractures enhance brine backflow,inhibiting CO2 migration and disrupting the uniform development of CO2 fingerings,leading to a decrease in CO2 concentration.Over time,however,they become preferential channels for CO2 migration,promoting its dissolution and storage capacity.In saline aquifers with fractures,the amount of dissolved CO2 can increase significantly by 11.03%with a fracture width of 0.1 mm,and this increase continues as the fracture width increases.The CO2 convective-mixing process is divided into three stages:rapid migration,relatively stable migration,and slow migration.The inclination angle and combination characteristics affect the CO2 diffusion path and the location and intensity of saline backflow.In a single low-angle fracture,dissolved CO2 migrates inward from both ends,with reflux occurring in the middle.By contrast,high-angle fractures caused dissolved CO2 to migrate upward through the lower oblique end with more concentrated and stronger reflux at the upper oblique end compared to low-angle fractures.In aquifers with combined fractures,horizontal parallel fractures create backflow patterns similar to low-angle fractures.Intersecting fractures help reduce backflow in the smaller area above them,while inclined parallel fractures help reduce backflow at the upper end of high-angle fractures.In large-scale fractured saline aquifers,well-developed intersecting fractures serve as primary channels for CO2 migration.They enhance the backflow effect in less developed or isolated fracture areas,inhibiting the formation of CO2 fine fingerings and reducing their number.These fractures also accelerate CO2 migration to deeper areas,improving its dissolution and storage.This work improves the understanding of CO2 transport and sequestration mechanisms in fractured saline aquifers and offers valuable guidance for evaluating the safety of CO2 sequestration in these environments.关键词
裂缝性咸水层/CO2 溶解封存/对流混合特性/离散裂缝网络/回流Key words
fractured saline aquifers/CO2 dissolution trapping/convective-mixing characteristics/discrete fracture network/backflow分类
能源科技引用本文复制引用
谭启贵,田键,田瑞超,彭浩平..裂缝对咸水层内CO2对流混合特性的影响[J].工程科学学报,2025,47(5):1117-1127,11.基金项目
国家自然科学基金资助项目(42407065) （42407065）
江苏省基础研究计划自然科学基金资助项目(BK20230647) （BK20230647）
江苏省高等学校自然科学研究面上资助项目(23KJD610001) （23KJD610001）
