Demonstration of Non-Endangerment at the Secarb Anthropogenic Test Site

Abstract

The Southeast Carbon Sequestration Partnership (SECARB) Anthropogenic Test became the first fully integrated carbon capture, transport, and storage project to successfully demonstrate non-endangerment towards the closure of a Alabama Department of Environmental Management (ADEM) underground injection control (UIC) permit. Despite being a state-issued UIC Class V experimental well permit, this permit contained many elements specific to geologic sequestration of CO2 included in the United States Environmental Protection Agency (EPA) regulations for Class VI wells. This paper will outline the permit structure and the steps taken to demonstrate non-endangerment for the first fully integrated Carbon Capture and Storage (CCS) project on a coal-fired power plant using advanced amines for CO2 capture. The SECARB Anthropogenic Test is a U.S. Department of Energy (DOE), Southern Company, and Electric Power Research Institute (EPRI) funded, Southern States Energy Board (SSEB) managed, project designed to demonstrate deep underground injection and containment of anthropogenic CO2 sourced from a 750 MW (net) coal -fired electric generating unit at Plant Barry, Alabama. From August 2012 to September 2014, a total of 114,104 metric tonnes of CO2 were captured and transported via a 12-mile pipeline from Alabama Power Company’s Plant Barry and successfully injected and stored in the upper Paluxy formation, a Lower Cretaceous sandstone unit, at the Denbury Onshore operated Citronelle Oil Field in Citronelle, Alabama. One CO2 injection well and three monitoring wells were drilled for this project. The initial Class V experimental technology UIC permit application was modified to include some Class VI permit requirements by the EPA to demonstrate protection of underground sources of drinking water (USDWs). These requirements included but were not limited to bottom to top cement coverage, a model-based Area of Review (AoR) determination with periodic updates, and a suite of Monitoring, Verification and Accounting (MVA) methods to track and monitor the CO2 plume migration and containment within the permitted injection zone. The UIC permit required extensive monitoring of the injected CO2 with objectives to create and sustain well integrity, assure safe CO2 injection operations, verify the location and migration of the CO2 plume, and monitor for any CO2 leakage. As such, a suite of technologies were applied and developed to demonstrate non-endangerment of underground sources of drinking water (USDW’s) and to ensure that CO2 does not migrate out of the intended storage zones. This involved several levels of monitoring: surface monitoring, shallow groundwater monitoring, and deep reservoir monitoring via commercially available and experimental MVA methods. Sufficient evidence was provided by the suite of monitoring efforts to indicate successful non-endangerment of USDWs at the Citronelle site. No CO2 release or build-up was detected using groundwater analysis, tracer detection, and soil CO2 flux monitoring to indicate any shallow or surficial leakage of CO2. Additionally, no evidence of gas saturation was observed within or above the confining zone, based on the results of time-lapse pulsed neutron capture logging. Cross-well seismic results show no negative velocity anomalies in or above the confining unit, which implies that there is no detectable leakage out of the injection zone. The associated models simulating the distribution of CO2 through the injected geological layers agreed with observed monitoring data, demonstrating confinement within the injected zone and confirming that the Citronelle Dome structure forms an ideal CO2 storage complex for the confinement of CO2 in the subsurface.