Integrated Framework for Assessing Impacts of CO₂ Leakage on Groundwater Quality and Monitoring-Network Efficiency: Case Study at a CO₂ Enhanced Oil Recovery Site

Abstract

This study presents a combined use of site characterization, laboratory experiments, single-well push-pull tests (PPTs), and reactive transport modeling to assess potential impacts of CO2 leakage on groundwater quality and leakage-detection ability of a groundwater monitoring network (GMN) in a potable aquifer at a CO2 enhanced oil recovery (CO2 EOR) site. Site characterization indicates that failures of plugged and abandoned wells are possible CO2 leakage pathways. Groundwater chemistry in the shallow aquifer is dominated mainly by silicate mineral weathering, and no CO2 leakage signals have been detected in the shallow aquifer. Results of the laboratory experiments and the field test show no obvious damage to groundwater chemistry should CO2 leakage occur and further were confirmed with a regional-scale reactive transport model (RSRTM) that was built upon the batch experiments and validated with the single-well PPT. Results of the RSRTM indicate that dissolved CO2 as an indicator for CO2 leakage detection works better than dissolved inorganic carbon, pH, and alkalinity at the CO2 EOR site. The detection ability of a GMN was assessed with monitoring efficiency, depending on various factors, including the natural hydraulic gradient, the leakage rate, the number of monitoring wells, the aquifer heterogeneity, and the time for a CO2 plume traveling to the monitoring well.

Arsenic mobilization in shallow aquifers due to CO2 and brine intrusion from storage reservoirs

“…Although As concentration exceeds the maximum contamination level (MCL) of the U.S. Environmental Protection Agency (EPA) in the beginning when CO 2 is introduced for both BG and S reactors, it drops below the MCL after 8-day exposure, which might not be considered as a long term concern of the USDWs. This As concentration drop was also observed in other studies 17, 30, 31 . It is notable that the BG reactor without CO 2 injection shows a large increase of aqueous phase As concentration to exceed the MCL.…”

Semi‐analytical approach to reactive transport of CO2 leakage into aquifers at carbon sequestration sites

“…Regional groundwater flows westward, with an average regional hydraulic gradient of about 0.5% in the site . Groundwater types are mainly Na‐Cl, Ca‐Na‐HCO 3 , and Ca‐Na‐HCO 3 ‐Cl . Mineral analysis of aquifer sediments indicates that quartz and kaolinite are the dominant minerals and few carbonates are present in the aquifer sediments.…”

“…One of the challenging questions to be addressed is to assess monitoring efficiency of a groundwater monitoring network (GMN) in the event of CO 2 leakage from possible failures of the 151 P/A wells. Yang et al . presented a reactive transport modeling approach to assess detection ability of 9 possible GMNs, with well density ranging from 0.1 well/km 2 to 0.9 well/km 2 …”

“…Yang et al . presented a reactive transport modeling approach to assess detection ability of 9 possible GMNs, with well density ranging from 0.1 well/km 2 to 0.9 well/km 2 …”

Identifying attributes of CO2 leakage zones in shallow aquifers using a parametric level set method

“…11 For example, Wang and Jeffe 8 conducted a series of numerical simulations of CO 2 release into shallow aquifers by coupling a reactive transport model with a geochemical speciation model. Yang et al 13 conducted both laboratory and field experiments to study the potential impact of CO 2 leakage on shallow aquifer water quality at a CO 2 enhanced-oil-recovery field. They demonstrated that a CO 2 leak with magnitude greater than 10 4 ton/yr can be detected at a monitoring well located 500 m downstream from the leak within 15 months and that pH and carbonate chemistry would offer good indicators of CO 2 intrusion in the scenarios they considered.…”