AVO modelling considering various caprock and reservoir scenarios for potential CO2 storage in Smeaheie area, northern North Sea

Unlike a hydrocarbon accumulation where we are sure of a working reservoir and the caprock integrity, the CO2 storage has many unknowns before the gas is injected and placed there. To reduce this risk it is imperative to model all the possible scenarios before taking a major decision for CO2 storage. To evaluate subsurface reservoirs and caprocks for CO2 sequestration, the CO2 plume movement while injection and subsequent changes in the elastic properties at the reservoir-caprock interface are important. The AVO method might provide us with a tool to detect the position and level of saturation of CO2 in a reservoir while and after injection. The upper Jurassic Sognefjord Formation is a potential CO2 storage formation overlain by the Heather and Draupne Formations considered to be the cap rocks in the Smeaheie area within the northern North Sea. In this study we considered two different reservoir-caprock cases with five different saturation, pressure and temperature scenarios for each case to check the sensitivity of the AVO method in this area. These findings will help understanding the change in elastic properties at the reservoir-caprock interface as a function of CO2 saturation, facilitating detection of its migration and possible phase changes.