Reservoir Characterization of Snøhvit Field, Norwegian Barents Sea

Snøhvit field is the only field in production in Norwegian Barents Sea. Most of the hydrocarbons are gas. Complicated tectonic history of this field resulted in low matured source rocks, highly faulted structures, low porosities and trap breach. Three reservoirs were studied in this project; Stø, Nordmela and Tubåen Formations. Stø is the main producing formation in Snøhvit field. It is gas saturated and formed in shallow marine environment. Most sections of Stø Formation are composed of very clean sands. Properties in Nordmela are much worse for its high volume of shale and clay contents formed in complex estuary and tidal environments. Only minor gas and oil were found in it. Clay studies show evidence of deep burial and uplifted history in this region. Although oil and gas did not exist in fluvial Tubåen Formation, it is the main object of study because it was the target formation of the previous CO2 injection project operated by Statoil. Four zones were divided in this formation but the uppermost one represents a transgression event rather than fluvial environments. Models of this formation explained the storage capacity problems. Different methods were used to estimate porosities and permeabilities for all three reservoirs. Calculations show previous overestimation of permeabilities and connectivity for channels. Local good CO2 warehouses were isolated and the surrounding worse reservoirs become barriers under high injection pressure. Statoil started a new injection target which is Stø Formation. A preliminary and qualitative analysis shows thick and widespread sandstones. These sandstones may support the long lasting injection project.