Abstract
CO2 resistant cement-zonal isolation technology dedicated to CO2 geological storage-provides an enduring solution to reducing well leakage risks in carbon capture and storage (CCS) and CO2 enhanced oil recovery (EOR) projects.
CCS involves capturing CO2 from the major sources of concentrated emissions and injecting it into selected geological formations such as saline aquifers, depleted hydrocarbon reservoirs and unminable coal beds. CCS has the potential to make a critical contribution to reducing the amount of greenhouse gas released into the atmosphere as the most effective, safe, and low-cost long-term CO2 storage technology.
One of the key requirements in CCS is long-term zonal isolation. Subsurface pressure and temperature changes can compromise the stability and integrity of the cement sheath around a CO2 injection well. Compromising well integrity can quickly lead to CO2 leakage at the surface, putting containment at risk. That's why the cement sheath used in the wellbore must be exceptionally durable and able to maintain its integrity for hundreds of years.
Portland cement has been used successfully for decades in oil and gas well cementing. However, such cements are thermodynamically unstable in CO2-rich environments and degrade once exposed to CO2 in the presence of water. For this reason, compromised well integrity has been identified as the greatest risk factor for leakage from underground storage sites.
CO2-resistant cement ensures lasting zonal isolation. In laboratory tests, the system proved highly resistant to CO2 attack, maintaining stable mechanical properties after exposure to simulated extreme injection/storage downhole conditions, including wet supercritical CO2 and water saturated with CO2. This cement system is 100% compatible with Portland cement and can be blended, mixed, and pumped using standard field equipment. It can be used for zonal isolation in new CO2 injection wells, or to plug and abandon existing CO2 injection/production wells at the end of a project.
