摘要
盖层密封性能对CO_2地质封存工程的容量、经济性、安全性具有重要影响。盖层岩石具有明显的层状非均质特点,而这种层状非均质特点直接影响CO_2在盖层中的迁移与泄漏过程,从而影响盖层的密封性能。现有研究考虑了各向同性的非均质性对盖层密封性能的影响,但并未针对层状非均质性盖层展开相应的研究。建立了考虑孔隙度、渗透率和毛管压力参数变化关系的均质、非层状非均质和层状非均质3种盖层地质模型,并采用TOUGH2对统一边界条件的不同地质模型开展了数值模拟对比研究,分析了CO_2进入盖层、盖层内迁移和穿透盖层而形成缓慢泄漏的全过程。模拟结果表明:3种模型中,自由态CO_2饱和度分布与孔隙度、渗透率的分布基本一致;与均值模型相比,非层状非均质性会加速CO_2在盖层中的迁移,而层状非均质性将会阻碍CO_2在盖层中的迁移,增加穿透时间;与均质模型和非层状非均质模型相比,层状非均质模型将会大大降低CO_2的穿透盖层以后的泄漏速率和泄漏总量。针对建模和数值模拟过程中遇到的问题,提出了盖层地质建模过程中的一些局限性。其结果为更加客观和定量地评价CO_2在盖层内迁移规律及泄漏量奠定了一定的基础。
The sealing ability of cap rock has a critical influence on the storage capacity, economy, and security in CO2 geological storage project. Due to the obvious characteristic of layered heterogeneity of the cap rock, it directly affects the migration and leakage process of CO2 in the cap rock. As a result, the cap rock sealing ability is also affected. Currently, the effect of isotropic heterogeneity on the sealing ability of cap rock was studied in the literature. However, the effect of layered heterogeneity has not been investigated yet. In this study, the homogeneous, non-layered heterogeneous and layered heterogeneous models were separately established by considering the different spatial distribution of porosity, permeability and capillary pressure of cap rock. Under consistent CO2 injection conditions, numerical simulations were conducted using these three models to comparatively study the whole leaking process of CO2 entering, migrating and breakthrough all over the cap rock by using TOUGH2. Results revealed that the distributions of free CO2 saturation in the cap rock agreed with the spatial distributions of porosity and permeability among the models. In contrast with the homogeneous model, non-layered heterogeneity accelerated the CO2 migration, whereas layered heterogeneity slowed down CO2 migration in the cap rock, and increased the period of CO2 breaking through the cap rock. Compared with the homogeneous and non-layered heterogeneous models, layered heterogeneous model greatly decreased the leakage rate and total leakage amount of CO2 after the breakthrough of CO2. At last, limitations on the geological modelling were addressed. Hence, the research results provide helpful guidance for more objective and quantificational evaluation on CO2 migration and leakage through the cap rock.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2017年第11期3287-3294,共8页
Rock and Soil Mechanics
基金
中国科学院战略性先导科技专项课题(No.XDA07040300)
中科院青年创新促进会支持(No.20140015)~~
关键词
CO2地质封存
盖层
层状非均质性
迁移
数值模拟
CO2 geological sequestration
cap rock
layered heterogeneity
migration
numerical simulation
