黄土塬地区CO2驱油封存泄漏地下水监测体系研究

针对鄂尔多斯黄土塬地区CO₂驱油封存项目的监测需求，在综合辨识黄土塬地区地下水潜在的CO₂泄漏特征，剖析CO₂泄漏进入地下含水层后的空间运移及时间响应特征的基础上，结合CO₂驱油封存过程，建立了1套面向黄土塬地区CO₂驱油封存CO₂泄漏的全时空立体化地下水监测体系。研究表明:受地形地貌及土壤特点影响，黄土塬地区驱油封存的CO₂具有盖层突破、井筒侧漏、降雨反渗和地表径流补给的多源泄漏特征；CO₂泄漏进入地下含水层后具有纵向快速运移扩散、横向四周缓慢扩散并随地下水向下游运移的空间运移特征和CO₂浓度、电导率等指标上升，pH值下降以及Ca2+、Mg2+离子浓度先上升后下降的时间响应特征。基于上述特征所建立的监测体系可为该区域CO₂驱油封存示范项目的监测提供参考。

DEVELOPMENT OF A GROUNDWATER MONITORING SYSTEM FOR CO2 LEAKAGE OF CO2-EOR STORAGE IN LOESS TABLELAND REGION

In view of the lack of literature in monitoring of CO₂ leakage into groundwater and the demand of the monitoring of CO₂-EOR and storage projects in the Loess Tableland Region in the Ordos Basin, in this study, based on comprehensive characterization of the potential CO₂ leakage into groundwater and identification of the spatial migration and time response characteristics of CO₂ leakage into groundwater, a full-time and three-dimensional monitoring system was established for monitoring CO₂ leakage into groundwater associated with CO₂-EOR process in Loess Tableland Region. The result indicated that, affected by topography and soil characteristics, the potential CO₂ leakage into groundwater featured with multiple leakage sources, including caprock breakthrough, shaft side leakage, rainfall infiltration and surface runoff recharge. The migration of CO₂ leaked into the groundwater were characterized with quick diffusion in the vertical direction, slowly spread out in the horizontal direction, and movement along with water flow to downstream. The time response characteristics were also identified with seven indicators to CO₂ leakage into groundwater, such as the increase of CO₂ concentration, conductivity, HCO₃- concentration, temperature and pressure, the decrease of pH value and the variation of Ca2+ and Mg2+ concentrations. The developed monitoring system reflecting above characteristics could provide solid support for the monitoring of CO₂-EOR and storage in Loess Tableland Region.