Ultrasonic measurements of attenuation and velocity of compressional and shear waves in partially frozen unconsolidated sediment and synthetic porous rock

The presence of partially frozen liquid in the pore spaces of porous materials has significant effects on elastic wave propagation. Although the characterization of partially frozen systems using velocity information has been well developed, application of the attenuation information is limited because the attenuation mechanisms in partially frozen systems are poorly understood. We have conducted ultrasonic wave transmission measurements with changing temperatures from 0 degrees C to -15 degrees C to estimate the effect of partially frozen liquids grown in unconsolidated (unconsolidated sediment) and consolidated (synthetic porous rock) materials on the velocity and attenuation of P- and S-waves. Our experimental results determined that the existence of partially frozen liquid in the unconsolidated and consolidated materials increases the velocity and attenuation for temperatures of 0 degrees C to around the freezing point (i.e., -3 degrees C), thus experimentally validating the unintuitive observations of high velocity and high attenuation. We interpreted the differences in velocity-versus-temperature curves as both the difference in inherent stiffness between the matrix of the consolidated material and the ice frame of the partially frozen unconsolidated material and the microscale ice distribution in pore spaces. We have also attributed the difference in the attenuation-versus-temperature curves in the unconsolidated and consolidated materials between the P- and S-waves to the difference of attenuation mechanism between the P- and S-waves. Our findings can be used for interpreting the velocity and attenuation results from the sonic logging measurements.