How do depleted oil and gas wells impact the safety and efficacy of carbon sequestration and storage? Researchers at Battelle recently completed a comprehensive analysis of historical oil wells in Ohio and Michigan to determine how they impact CO2 storage risks in different areas of the states. The data is now available as a map to help stakeholders in the oil & gas and power industries pinpoint the areas most likely to be viable for carbon storage.
There are over one million depleted oil wells throughout the Midwestern United States, some dating back to the mid 1800s. Many of these wells are located in areas where power companies and other carbon-intensive industries would benefit from using carbon capture, utilization and storage (CCUS) methods to reduce their carbon footprints. However, little was known about the current condition of these wells and how their condition changes over time. Degraded wells can act as conduits to allow carbon injected into local reservoirs to escape back into the atmosphere.
The three-year project, funded by the Department of Energy (DOE) and completed in partnership with BP and Columbia NiSource, examined historical logs and records—including construction and operational data and geophysical logs—to complete a survey of depleted wells in Ohio and Michigan. Wellbore integrity testing was completed on representative wells to determine how age, material construction and other factors have impacted the studied wells. Testing included evaluation of cement degradation, cracks and microannuli, acid-gas zones, channeling and casing corrosion. Sustained pressure casing monitoring was completed for 13 representative wells.
Using this data, researchers were able to determine how different characteristics impact wellbore integrity and develop maps that correlate well characteristics and potential risks across both states. By looking at test results for the representative wells, researchers can now predict the condition of wells of similar age, material construction, depth and geologic conditions. Researchers applied this analysis to 240,000 abandoned and depleted wells in Ohio and 60,000 in Michigan to develop regional datasets that predict potential local wellbore integrity risks with a high degree of confidence.
The maps identify which zones are likely to be safe for CCUS and which zones will require mitigation to make them safe for long-term carbon storage. The analysis showed that some areas previously considered too risky for CCUS are in fact most likely safe because the wells present are not deep enough to penetrate the geologic storage zone. By contrast, analysis of wells in other areas identified the likelihood of cracks and defects that would permit CO2 to escape over time. The dataset also identifies wells with limited records that would require further characterization.
This is the first detailed analysis of wellbore integrity for wells in Ohio and Michigan. The oil & gas and power industries will be able to use the data to determine which areas are most viable for CCUS and estimate the amount of mitigation needed for safe CO2 injection and storage in their regions. Researchers at Battelle are now beginning a follow up project in Michigan to see how exposure to CO2 impacts wellbore integrity over time.