Assessing storage potential and leakage risks of geological carbon dioxide reservoirs

What is it about?

As part of Norway’s efforts to meet the Paris Agreement goals to reduce carbon dioxide (CO₂) emissions, the country is looking towards carbon capture and storage (CCS) in natural geological reservoirs, by injecting CO₂ hundreds of metres underground. But while CO₂ exists as a gas in nature, it needs to be compressed into a liquid or supercritical form (a mixture of liquid and gaseous phases) for transportation, injection, and storage in such reservoirs. Because of the unique physicochemical and flow properties of CO₂, which vary with temperature and pressure, potential sub-surface geological storage sites must be assessed for their storage conditions, capacity, and possible leakage risks. This study analysed the CO₂ storage prospects in the Smeaheia area, part of the offshore Horda Platform in Norway. It explored the structural geology of and fault blocks (cracks in the earth’s crust along which tectonic movements occur) in the region, with specific reference to two exploration sites. The study also addressed potential containment and leakage risks, through fault seal analyses, pressure profile predictions, and geochemical and geo-mechanical assessments. These analyses revealed that the structure at one of the two exploration sites has low fault-related containment risks, while the other site presents higher risks, and thus, storage uncertainty, due to its proximity to the Precambrian Øygarden Fault System.

Featured Image

Photo by Matthias Heyde on Unsplash

Photo by Matthias Heyde on Unsplash

Why is it important?

CCS possibilities in natural reservoirs are being increasingly explored as a means to contain the atmospheric accumulation of CO₂ and its contribution to global warming. Geological sub-surface rock formations serve as potential long lasting (up to even 1000 years) CO₂ reservoirs. Evaluating the structural properties of potential reservoirs, particularly fault seals, is key to avoiding CO₂ leakage back into the atmosphere or into surrounding areas. KEY TAKEAWAY: Understanding the fault seal features and pressure dynamics of potential CO₂ reservoirs can help scale up CCS potential and minimise leakage.