RELATIONSHIPS AMONG COMPRESSIONAL WAVE ATTENUATION, POROSITY, CLAY CONTENT, AND PERMEABILITY IN SANDSTONES

We have measured the attenuation coefficients of compressional waves in 42 sandstones at a confining pressure of 40 MPa (equivalent to a depth of burial of about 1.5 km) in a frequency range from 0.5 to 1.5 MHz. The results show that for these samples, compressional wave attenuation (α, dB/cm) at 1 MHz and 40 MPa is related to clay content (C, percent) and porosity (φ, percent) by α = 0.0315φ + 0.241C - 0.132 with a correlation coefficient of 0.88. The relationship between attenuation and permeability is less well defined: Those samples with permeabilities <50 md have high attenuation coefficients while those with permeabilities >50 md have low attenuation coefficients at 1 MHz at 40 MPa. These experimental data can be accounted for by modifications of the Biot theory and by consideration of the Sewell/Urick theory of compressional wave attenuation in porous, fluid-saturated media. -from Authors