深部储层中CO2沿断层泄漏量的影响因素

CGS（CO₂地质储存）是CO₂减排的重要手段之一，天然裂隙的存在则是CGS的潜在风险.CO₂地质储存过程中储层上覆盖层及其浅部含水层是防止CO₂泄漏的天然屏障，为了探究深部咸水层中CO₂沿断层的泄漏过程并获得断层渗透率及储层中超临界CO₂流体初始条件（初始饱和度、初始泄漏压力）对CO₂沿断层泄漏速率和泄漏量的影响程度，依据鄂尔多斯CO₂灌注工程示范区资料，使用多相、多组分溶质运移数值模拟软件TOUGH2建立了2D概念模型.结果表明，深部咸水层中的CO₂在压力差和浓度差的作用下沿断层发生泄漏，到达浅部含水层后开始发生侧向运移，100 a内运移了约200 m的水平距离；由于浮力的作用，CO₂集中在含水层顶板处，有效地防止了CO₂向外泄漏.影响因素分析表明，100 a内断层渗透性能为低渗、中渗和高渗条件时，CO₂累积泄漏量分别为0、1 050和3 000 t；CO₂初始饱和度分别为0.20、0.50和0.99时，CO₂累积泄漏量分别为550、1 050和1 650 t；初始泄漏压力分别为17.3、17.6和18.1 MPa时，CO₂累积泄漏量则分别为900、1 050和1 400 t.除此之外，断层渗透性、CO₂初始气体饱和度和初始泄漏压力对CO₂泄漏的影响还体现在泄漏发生时间和平均泄漏速率上.研究显示，各因素对CO₂沿断层泄漏过程的影响程度表现为断层渗透性能> CO₂初始饱和度> CO₂初始泄漏压力. 

Factors Influencing Amount of CO2 Leakage through a Fault Zone in Deep Storage Aquifer

Carbon dioxide geological storage (CGS) is one of the important ways to mitigate CO₂. However, the presence of natural fractures is a potential risk of CGS. The cap rock and shallow aquifers covering a CO₂ reservoir may be a natural barrier to prevent CO₂ from leaking. According to the data of Ordos CO₂ storage demonstration site, we established a 2D conceptual model based on the migration theory of multi-component and multiphase flow, using the numerical simulation software TOUGH2 to study the process of CO₂ leakage along a fault from a deep saline aquifer, and to analyze the influence of fault porosity, permeability and the initial conditions of CO₂ fluid (initial saturation, leak pressure) on the amount of CO₂ leakage along the fault. The results showed that CO₂ in deep saline aquifer will leak along the fault under the action of pressure difference and concentration difference, and then migrate laterally in the shallow aquifer. The distance of migration is about 200 m in 100 years. CO₂ will be concentrated on the top because of buoyancy, and the aquifer can effectively prevent the leakage of CO₂. The analyses of uncertain parameters showed that the accumulation of CO₂ leakage was 0, 1050 and 3000 t when fault permeability was low, medium and high respectively over 100 years, and the accumulation of CO₂ leakage was 550, 1050 and 1650 t when CO₂ initial saturation was 0.20, 0.50 and 0.99 respectively. Moreover, the accumulation of CO₂ leakage was 900, 1050 and 1400 t when CO₂ initial leak pressure was 17.3, 17.6 and 18.1 MPa respectively. In addition, the leakage time and average leakage rate of CO₂ have to do with the different levels of these three factors, and the effects of each influencing factor in the process of CO₂ leakage can be arranged as follows:fault permeability > CO₂ initial saturation > CO₂ initial leak pressure.