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Categorizing CO2 Storage Potentials
We use mathematical optimization to suggest practical injection strategies and storage efficiencies of large-scale saline aquifers. The optimal injection rates are limited due to excess leakage and/or pressure buildup, which is forecast or simulated to occur, respectively. Based on these limitations, we can categorize the formation as "leakage-constrained", "pressure-constrained", or constrained in terms of both leakage and pressure. The following three formations demonstrate each possible category. Their optimal injection strategies were obtained using a 30-year injection period and a leakage penalty factor of 5. More details of these storage examples can be found in [1].

Pressure-contrained storage example
 

Bjarmeland (Barents Sea)

The depths of this formation range from 500 to 2150 meters below sealevel, so the overburden pressure varies from 7 to 35 MPa. The optimal injection rates of the five wells are such that the formation pressure builds up to the pressure limit, which was set to be 90% of the overburden pressure. An insignificant amount of leakage occurs. Thus, this storage case is categorized as "pressure-constrained".
     

Leakage-constrained storage example
   

Statfjord (North Sea)

Parts of this formation are located at depths of 6.1 kilometers below sealevel, thus the overburden pressure is as high as 114 MPa. Four wells were placed around these deep regions, according to the trapping structure of the topsurface. The induced pressure rise remains well below the pressure limit. However, the optimized storage strategy includes an amount of CO2 leakage, thus this storage case is categorized as "leakage-constrained".
     

Both pressure- and leakage-constrained storage example
   

Tilje (Norwegian Sea)

The overburden pressure in this formation varies from 19 to 55 MPa. Seven wells are placed according to the trapping structure of the top surface, several of which are located within the deepest region. The optimized storage strategy includes an amount of CO2 leakage as well as a pressure rise that reaches the limit. Thus, this storage case is categorized as both "pressure- and leakage-constrained".



Literature

  1. R. Allen, H. M. Nilsen, O. Andersen, K.-A. Lie. Categorization of Norwegian Continental Shelf formations in terms of their geological CO2 storage potentials*. 13th International Conference on Greenhouse Gas Control Technologies, GHGT-13, 14-18 November 2016, Lausanne, Switzerland.
    * revised version in which we corrected inaccuracies in the calculation of overburden pressure that determines the storage efficiency and whether an aquifer is constrained by leakage or pressure buildup

Published December 9, 2016