Abstract: Evaluation method and risk control of CO₂ leakage are key issues for carbon capture and storage（CCS).In order to reveal affecting factors and features of CO₂ leakage during injection, a two-phase flow model was proposed to describe the leakage process, and numerical simulations were conducted using a commercial software COMSOL Multiphysics 3.5a.Based on comparison and extension of its solutions for a benchmark problem, the affecting factors, including distance between the injection well and leaky path, radius and permeability of leaky path, injection rate and injection depth, were investigated. The quantitative relationships between leakage rates and impact factors were obtained from simulations and data analysis.The results show that asymptotic leakage rates of CO₂ are linearly dependent on the reciprocal of distance between the injection well and leaky path, are quadratic with radius of leak path, and are linear with respect injection rates.The permeability of leaky path is the key factor controlling CO₂ leakage, whereas the increase of injection depth has little effect on decreasing CO₂ leakage rates.The proposed model and simulation results not only reveal the relationship between CO₂ leakage rates and impact factor quantitatively, but also provide analytical method and computational tools for site selection, evaluation of leakage and risk management of CO₂ injection into subsurface formations.

Key words: CO₂ storage, leakage, numerical simulation, prediction

摘要： 地下封存CO₂泄漏的评估方法和风险控制是碳捕集和封存（CCS）技术亟待解决的核心问题。为了揭示封存CO₂泄漏过程的影响因素及其特性，本文建立两相流驱替过程数学模型描述封存CO₂的泄漏过程，采用COMSOL Multiphysics 3.5a软件进行数值模拟。通过对基准问题及其解的拓展，分别对注入井与泄漏通道之间距离、泄漏通道半径、泄漏通道渗透率、CO₂注入速率和CO2注入深度等因素对封存CO2泄漏过程的影响特性进行研究，通过过程模拟和数据分析得到了影响因素的定量函数关系。研究表明：封存CO₂的渐近泄漏速率与注入井与泄漏通道之间距离倒数呈对数线性关系，与泄漏通道半径呈抛物线型关系，与注入速率呈线性关系；泄漏通道的绝对渗透率是CO₂泄漏速率控制的关键因素，而CO₂注入深度的增加并不能有效地降低CO₂泄漏速率。本文的计算模型和数值模拟结果不仅揭示了地下封存CO₂泄漏过程的影响因素与泄漏速率之间的定量关联规律，还可为地下封存CO₂的封存地点选择、泄漏速率估计和泄漏风险评估提供工程分析方法和计算工具。

关键词: CO₂封存, 泄漏, 数值模拟, 预测