Dynamic modelling of a UK North Sea saline formation for CO₂ sequestration

Preliminary dynamic modelling, using TOUGH2/ECO2N, has been carried out to assess the suitability of a site in the UK North Sea for sequestering CO₂. The potential storage site is a previously unused saline formation within the Permian Rotliegend sandstone. Data regarding the site are limited. Therefore, additional input parameters for the model have been taken from the literature and nearby analogues. The sensitivity of the model to a range of parameters has been tested. Results indicate that the site can sustain an injection rate of around 2.5 Mt a^-1 of CO₂ for 20 years. The main control on pressure build-up in the model is the permeability of the unit directly beneath the Rotliegend in the location of the proposed storage site. The plume diameter is primarily controlled by the porosity and permeability of the site. A comparison between static, analytical and dynamic modelling highlights the advantages of dynamic modelling for a study such as this. Further data collection and modelling are required to improve predictions of pressure build-up and CO₂ migration. Despite uncertainties in the input data, the use of a full three-dimensional (3D) numerical simulation has been extremely useful for identifying and prioritizing factors that need further investigation.