Isotopic composition of geologic organic matter and its applicability in reducing greenhouse gas emissions

Jaime Cesar, Omid H. Ardakani, Edward Little

Geological Survey of Canada. Calgary, AB 

Driving Canada to become a cleaner energy producer requires the petroleum industry to decrease the carbon footprint of not only current production operations but also that of ceased activities. In this respect, carbon emissions from abandoned/orphan wells represent a critical challenge for the energy industry. In Alberta alone, the number of orphan wells surpassed 8,600 in 2020, with a national cumulative estimate cost for well clean-up of $361 million (Office of the Parliamentary Budget Officer, 2022). Petroleum wells are abandoned after their operating life ends. The process of abandonment includes the plugging of the well, removal of the wellhead, cutting, capping and burying the casing 1 m or more below the surface (Wisen et al., 2020). After abandonment, the integrity of the well can deteriorate over time and unexpected hydraulic connections between geologically isolated intervals can take place, which is known as wellbore leakage (Wisen et al., 2020). Leaking hydrocarbons can contaminate shallow aquifers and surface water, and will contribute to greenhouse gas (GHG) emissions. The stable carbon isotopic composition of leaking hydrocarbon is key in determining its source, thus influencing decision making when remediating deteriorated sections of a well from a given gas leak. Carbon isotopic composition information also helps tracking migration pathways of leaking gas into the shallow hydrosphere. However, several gaps persist in carbon isotope measurements of gas hydrocarbons. For instance, results can significantly vary according to sampling methods. This raises some critical questions such as (1) Is a 0.5‰ precision enough to distinguished gas sources that may be only 1‰ apart (e.g. many cases in Western Canada)? (2) Do enough legacy isotope data exist for multiple stratigraphic intervals produced in the past? (3) Is there enough carbon isotope data being generated now so that potential leakages can be addressed in the future?
Our presentation will discuss these issues and will explore carbon isotope instrumental analytical improvements that may be necessary to help meet the 2050 goal of net zero emissions.
 

References:
Office of the Parliamentary Budget Officer, 2022. Estimated cost of cleaning Canada’s orphan oil and gas wells. Office of the Parliamentary Budget Officer, Ottawa, Canada.
Wisen, J., Chesnaux, R., Werring, J., Wendling, G., Baudron, P., Barbecot, F., 2020. A portrait of wellbore leakage in northeastern British Columbia, Canada. PNAS 117(2), 913-922.