Ultrasonic properties of oil-well drilling muds

It is shown that the effective density (acoustic impedance/acoustic velocity) of heavily weighted muds can be significantly reduced compared to the static density because of the inertia of the suspended particles. The properties of weighted muds are qualitatively consistent with the Biot theory, in which viscous and inertial effects are dominant, but the viscosity is an ill-defined quantity and good agreement with theory is obtained only if the viscosity is assumed to be an order of magnitude less than the measured value. The attenuation in an oil-base emulsion is nonnegligible and appears to be caused by both thermal and viscous effects