1,4 (%quartz in matrix) ? 20 ,5 . But this is limited to non-smectitic and non-organic shales. So it's not applicable to Nordland shale (<2% of smectite). A correction or simplification of this problem was suggested by Lindeberg (1997). He considered a pressure difference for CO2 and water wet shale pore as in the following equation :
Δp = 2 σ/r,
where Δp = pressure difference in Mpa and σ = water wet shale pore in mN/m.
The prediction of pressures of capillarity for Nordland shale show the trapping of CO2 column for this formation varying from 11469, 1063 and 1188 m high .
Other measurements of sealing capacity of caprock were done by Dewhurst et al. (2002) for Muderong Shale in the northern Carnarvon Basin, northwest shelf of Australia. They have used this equation
Pc = 4γcos θ/d,
where γ is interfacial tension and θ is the contact angle between fluid and solid. The nature smectitic of this shale (28% of smectite, it is the main clay mineral of this rock) impose a contact angle of 140° as described by Diamond (1970). If the shale was more illitic or kaolinitic the contact angle would have been 150°. Then for Muderong shale an adaptation of the last equation has been created.
Pbh = Pc (γhCosθh)/(γCosθ) ,
where Pbh is a pressure sub-surface brine-hydrocarbon and γh and θh are interfacial tension and contact angles for the rock-brine-hydrocarbon system.
Updating the last equations and focalizing on Nordland Shale we have noted a diminution of the column height of CO2 but not meaning an inefficacy of the sealing.
