Potential injection sites for the storage of CO₂ were assessed using regional geological analysis, 3D seismic data, sampling, image logs and core data. The chosen site, near Krechba, is the downdip of the gas producing field. The reservoir comprises a relatively narrow, 20 metre-thick Carboniferous sandstone, 1900 metres underground, with low porosity (13-20%) and permeability (10mD). This is sealed by 950 metres of Carboniferous mudstones, then a 900 metre of Cretaceous sandstone and mudstone. Detailed geological and reservoir models of the reservoir, aquifer and caprock system have been constructed using the collected data.

State-of the-art drilling was necessary to access this narrow reservoir site. Three horizontal injectors (1500-1800 metres long) were drilled perpendicular to the stress field using geosteering technologies to maximise injection capacity.

Storage formation overview:

• Injection formation: 20 metres-thick Carboniferous sandstone
• Porosity and permeability: 13-20% porosity and 10mD permeability (very similar to potential deep saline CO₂ storage formations in many parts of the world)
• Injection depth: 1950m below ground with 13-20% porosity
• Wells: three, state-of-the-art, horizontal wells were drilled to inject the CO₂