WHITE MODEL OF ATTENUATION IN ROCKS WITH PARTIAL GAS SATURATION

In two important papers, J.E.White and co-authors (White, 1975; White et al, 1976) have given an approximate theory for the calculation of attenuation and dispersion of compressional seismic waves in porous rocks filled mostly with brine but containing gas-filled regions. Modifications of White's formulas for kE and Q in the case of gas-filled spheres brings the results into good agreement with the more exact calculations of Dutta and Ode (1979 a, b, see above), who used Biot's theory for porous solids. In particular, the modified formulas give the expected Gassmann-Wood velocity at very low frequencies. Inclusion of the finite gas compressibility in numerical calculations for gas-filled spheres shows an interesting maximum of the attenuation at low gas saturations which is not seen if the gas is ignored. A comparison of the attenuation calculated for the same rock and fluids but for three different geometries of the gas-filled regions suggests that the configuration of the gas-filled zones does not have an important effect on the magnitude of the attenuation.-Authors