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This paper deals with the problem of disposal of industrial waste greenhouse gases (CO2) into deep reservoirs. The simulator TOUGH2 was used to model the injection of 100 kg/s of COz for 10 years into an aquifer 3 km deep with the object of evaluating the long-term storage prospects for this gas. Depending on the permeability structure above the injection point, some gas may escape to the surface. In the most favourable case, all of the gas dissolves into the water, and the resulting dense fluid settles in the aquifer over several thousand years. Consequently, underground storage provides a promising sink for reducing CO2 emissions to the atmosphere.

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It is shown that the dimension of the vector space of second order, trace-free conformal Killing tensors (CKT’s) in a Riemannian space of dimension n (?3) is bounded above by (1/12)(n−1)(n+2)(n+3)(n+4) and that this is attained in flat space. The discussion is eventually restricted to four-dimensional spaces which admit a two-dimensional, Abelian, orthogonally transitive symmetry group, as well as one nonredundant CKT. A sufficient condition is given for an empty space to be Type D.