CO₂入侵包气带对土壤热参数的影响

张青海 邓红章 赵晓红 韩枫 李春荣 裴宇 张徽

摘 要： CO2地质储存是一种缓减碳排放行之有效的途径，但是逃逸的CO2入侵包气带将带来土壤热性质的变化。土壤包气带热参数直接控制着大气环境和土壤的热量交换，进而影响土壤的生态环境。为了研究土壤包气带热参数对高浓度CO2的响应规律，采用人工模拟CO2在包气带中泄漏的方法，通过检测CO2在土壤中的扩散规律并通过测试土壤含水率、干容重及热参数来研究CO2对土壤热性质的影响。结果表明：在实验设定的CO2浓度范围内，从低区到高区随CO2浓度升高，包气带热导率平均值由0.9 W/mK减小到0.5 W/mK，体积热容量由1.5减小到1.2 MJ·m-3·K-1；低浓度区土壤包气带体积热容量对CO2的敏感性高于热导率；不同CO2浓度影响了体积热容量与含水率的线性关系，低浓度区具有最好的线性关系，线性回归相关系数R2为0.741 9。在设定的CO2浓度梯度内CO2对土壤包气带热参数的影响有特定的规律，为研究CO2对土壤包气带热量传递奠定了基础。

关 键 词：CO2；土壤包气带；体积热容量；热导率

中图分类号：X 131.3 文献标识码： A 文章编号： 1671-0460（2016）04-0668-05

Abstract： Carbon dioxide geological storage is an effective way to mitigate carbon emission； but once the leaking CO2 invades into the soils unsaturated zone， the soil thermal properties will change. The thermal parameters in the unsaturated zone directly control the heat exchange of atmosphere and soil， therefore， the change of which can affect the ecological environment of soil. In order to study the effect of high concentration of CO2 permeation into the soils unsaturated layer on the thermal parameters， the experiment applied artificial simulation process of CO2 leakage into unsaturated zone to detect the transportation rule. By testing the soil moisture， dry bulk density and thermal parameters， the impact of CO2 on the soil thermal properties was studied. The results show that，within the range of experimental settings， with increase of CO2 concentration from low density regions to high density regions， the average thermal conductivity value of the vadose zone reduces from 0.9 W / mK to 0.5 W / mK， the volumetric heat capacity reduces from 1.5 to 1.2 MJ·m-3·K-1. The soil vadose zones volumetric heat capacity in the low density regions is more sensitive than the thermal conductivity. And different CO2 concentrations might affect the linear relationship between volumetric heat capacity and moisture content， the low CO2 test areas have the best linear relationship with the linear regression correlation coefficient R2 =0.7419. In the range of CO2 concentration gradient settings， the effect of CO2 permeation into the unsaturated zone on soil thermal parameters has specific rules， these results can be used for further research on the unsaturated zones heat transfer.

Key words： Carbon dioxide； Soil unsaturated layer； Volumetric heat capacity； Thermal conductivity

随着全球气候变暖，二氧化碳减排已经受到社会的普遍关注。目前，CO2地质埋存主要有三种形式：一种是利用CO2提高石油采收率（CO2-EOR），在实现CO2减排的同时，又可以提高油气采收率，实现双赢而备受世人注目[1，2]，另外两种是把CO2封存于不可开采的煤层和不适宜为人类所利用的深部咸水层[3]。然而，CO2地质埋存过程是相当复杂的，地质裂隙、地震等自然因素和废弃井或现有钻井的不封闭处理等人为因素均会造成埋存的CO2发生泄漏[4]。……