Verification Well #1: How a Deep Monitoring Well Was Used and Adapted to Meet the Evolving Monitoring Needs and Challenges at the Illinois Basin – Decatur Project

Abstract

The Illinois Basin – Decatur Project is a one million tonne deep saline geologic carbon dioxide (CO2) storage project led by the Midwest Geologic Sequestration Consortium, one of the United States Department of Energy – National Energy Technology Laboratory’s Regional Carbon Sequestration Partnerships. The project is currently in the post-injection monitoring phase and is using a monitoring well known as Verification Well #1 (VW1) that was drilled to a depth of 2,201 m (7,264 ft). When the well was first completed, it included an experimental Westbay multilevel monitoring system. That system was used for about six years to collect information from 11 monitoring zones including continuous temperature/pressure and 103 fluid samples. In addition, sequential pulsed neutron logging was an essential monitoring tool to identify CO2 presence and assess the evolution of annular, wellbore, and reservoir conditions. Geochemical sampling provided detailed fluid chemistry and helped verify pulsed neutron logging results. VW1 has served as an integral data source to understand the subsurface geology, document pre-injection conditions, evaluate the performance of experimental monitoring systems, monitor responses of the reservoir to injection, provide data for multiple numerical modeling efforts, conduct research on deep brines of the Illinois Basin, and verify containment of injected CO2. During the project, the post-injection monitoring needs for VW1 were increased significantly from 7 years to 22 years. Given the significantly extended timeframe and performance issues with the experimental system, five recompletion options were assessed, and a 3-zone, Baker Hughes intelligent completion system was selected. The recompletion offered a rare opportunity to evaluate the experimental Westbay system and wellbore integrity after six years of service in a highly corrosive environment. Cement integrity across the zones exposed to carbonated fluids appeared to be unchanged. However, localized pitting of the long string casing was observed in sections within the Mt. Simon Sandstone where casing internal yield strength had an estimated average degradation of 25%. Despite the corrosive environment, the specialized well construction materials, including 13Cr casing, proved crucial in maintaining VW1 integrity for continued monitoring purposes. The Baker Hughes system was successfully installed in 2017, and VW1 is scheduled to continue operation through 2032.