  We use virial series to study the equilibrium properties of confined
soft-spheres fluids interacting through the inverse-power potentials. The
confinement is induced by hard walls with planar, spherical and cylindrical
shapes. We evaluate analytically the coefficients of order two in density of
the wall-fluid surface tension $\gamma$ and analyze the curvature contributions
to the free energy. Emphasis is in bending and Gaussian rigidities, which are
found analytically at order two in density. Their contribution to $\gamma(R)$
and the accuracy of different truncation procedures to the low curvature
expansion are discussed. Finally, several universal relations that apply to
low-density fluids are analyzed.
