Potential chemical impacts of CO2 leakage on underground source of drinking water assessed by quantitative risk analysis

摘要

Many geologic carbon storage site options include not only excellent storage reservoirs bounded by effective seal layers, but also Underground Sources of Drinking Water (USDWs). An effective risk assessment and mitigation plan provides maximum protection for USDWs, to respect not only current policy but also to accommodate likely future USDW-specific regulatory protections. The goal of this study is to quantify possible risks to USDWs, specifically risks associated with chemical impacts on USDWs. Reactive transport models involve tremendous computational expense. Therefore, a secondary purpose of this study is to develop, calibrate and test reduced order models specifically for assessing risks of USDW chemical impacts by CO2 leakage from a storage reservoir. In order to achieve these goals, a geochemical model was developed to interpret changes in water chemistry following CO2 intrusion. A response surface methodology (RSM) based on these geochemical simulations was used to quantify associated risks. The case study example for this analysis is the Ogallala aquifer overlying the Farnsworth unit (FWU), an active commercial-scale CO2-enhanced oil recovery field. Specific objectives of this study include: (1) to understand how CO2 leakage is likely to influence geochemical processes in aquifer sediments; (2) to quantify potential risks to the Ogallala groundwater aquifer due to CO2 leakage from the FWU oil reservoir; and (3) to identify water chemistry factors for early detection criteria.