The cylindrical model is discussed and a new tube model is proposed to describe capillary imbibition kinetics in porous sedimentary rocks. The tube consists of a periodic succession of a single hollow spherical element of which the geometry is defined by the sphere radius and the sphere access radius. These two parameters are estimated experimentally for four rock types from their specific surface areas. Introducing those parameters in the model capillary imbibition kinetics, parameters are calculated and compared with the experimental ones. A direct relation between imbibition kinetics and specific surface area has been pointed out.