Theme 4: Analog Studies [PDF]
Improve understanding of the long-term fate of CO2 through examination of analogs, especially the CO2–enhanced oil recovery (EOR) sites to (1) assess environmental impacts of CO2 leakage from the storage formations and (2) test and validate monitoring tools and strategies for CO2 leakage detection in near-surface environments.
- Conducted groundwater chemistry survey at two CO2-EOR industrial analog sites: Cranfield site, Mississippi, and Hastings site, Texas, for understanding the complexity of geochemical processes dominating groundwater quality.
- Conducted a set of laboratory experiments with groundwater and sedimentary samples collected from various major aquifers in Texas to study the effects of CO2 leakage on groundwater quality.
- Developed numerical models to simulate the laboratory experiments and field tests.
- Conducted controlled-release tests at the ZERT site, Montana, for validating the process-based approach and applied this approach to CO2 leakage detection at the Cranfield and Weyburn sites in Texas and Canada.
- Completed a preliminary study of gas migration through the overburden, including
• Identification of a possible microseep at a field prior to and during progress of a CO2 flood and collection of five years of data on changes in fluid composition and isotopes.
• Implementation of aerial magnetic and conductivity surveys and initialization of laboratory simulations of gas migration.
Studies of analogs have resulted in the development of the following new geochemical methods:
- An integrated approach [PDF] combining numerical simulations, laboratory experiments, and field single-well push-pull tests to assess potential impacts of CO2 leakage on groundwater quality and test groundwater chemistry monitoring for CO2 leakage detection.
- A process-based approach [PDF] that can promptly identify a leakage signal using three simple relationships among coexisting gases (CO2, N2, O2, and CH2) to distinguish processes acting in the near surface.
- A novel methodology [PDF] using light hydrocarbon as a potential proxy for CO2 leakage detection. Methane migration through overburden to near-surface environments is well known, and methane is less attenuated by dissolution into water than CO2 is.
Major Field Sites
- Brackenridge Field Laboratory (BFL). An important research site in Austin, Texas, where various controlled-CO2-release tests can be conducted in the shallow aquifer and also the vadose zone.
- Cranfield site, Mississippi. An active industrial site with significant EOR activity where we studied groundwater and soil gas chemistry.
- Hastings site, Texas. An oil field near Houston undergoing EOR where GCCC has helped develop a monitoring plan for the field.
- ZERT site, Montana. A research field site where the process-based approach was validated for the detection of CO2.
- Kerr Farm, Weyburn, Canada. Adjacent to a field undergoing EOR where the process-based approach was applied to investigate a suspected CO2 leak.