Soil gas monitoring at the Illinois Basin – Decatur Project carbon sequestration site

Hongbo Shao, David A.N. Ussiri, Christopher G. Patterson, Randall A. Locke, Hong Wang, Alexander H. Taylor, Hanna F. Cohen

Research output: Contribution to journalArticlepeer-review


An extensive monitoring, verification, and accounting (MVA) program was carried out from 2011 to 2016 as part of the Illinois Basin – Decatur Project (IBDP), a large-scale carbon capture and storage (CCS) demonstration project in Decatur, Illinois, USA. As part of the monitoring program, a near-surface monitoring network for soil gas was used to characterize the natural variability of CO2 and identify anomalies that could be associated with CO2 leakage in the vadose zone. In the fall of 2011, 21 permanent soil gas sampling nests were installed on-site and three nests were installed off-site as reference locations. Soil gas was collected from three depth intervals (15–30, 47–61, 107–122 cm) at each nest. Fixed gas (CO2, N2, O2, and light hydrocarbon) concentrations, stable carbon isotopic composition (δ13C), and radiocarbon (14C) content of CO2 in soil gas were monitored during the pre-injection, injection, and post-injection phases from 2011 to 2016. Both CO2 concentrations and carbon isotopic compositions showed large spatial and temporal variations; however, the relationships among CO2, N2, and O2 concentrations in soil gas indicated that these variations should be attributed to natural processes and not CO2 leakage. Soil CO2 concentrations responded to temperature and precipitation variations and increased with increasing soil depth. While 14C cannot be used to determine the occurrence of CO2 leakage at IBDP site due to the indistinctive signature between injected CO2 and soil gas CO2, experiences at IBDP validated that δ13C can serve as an effective natural tracer at this site. Results from this project have value for future industrial CCS projects that plan to use soil gas monitoring techniques for site characterization and leakage detection.

Original languageEnglish (US)
Pages (from-to)112-124
Number of pages13
JournalInternational Journal of Greenhouse Gas Control
StatePublished - Jul 2019


  • Carbon capture and storage (CCS)
  • Carbon isotopes
  • Fixed soil gases
  • Illinois Basin – Decatur Project (IBDP)
  • Leakage detection
  • Soil gas monitoring

ASJC Scopus subject areas

  • Pollution
  • General Energy
  • Management, Monitoring, Policy and Law
  • Industrial and Manufacturing Engineering


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