The Effects of Carbonate Micro-structure on Seismic Velocities

To accurately study the factors that affect seismic velocity in carbonate rocks one should look at the texture, grain types, mineralogy, pore types and pore size of the rock as all these elements influence the seismic velocity of the rock. Compressional and shear wave velocities (at 1 MHz) of thirty-seven Arab-D rock samples were measured dry, and as functions of saturating fluid and confining pressure. The lithology, mineralogy, porosity, and pore type and size distribution of each sample were obtained using a combination of thin-section and scanning electron microscopy, helium porosimetry, and mercury intrusion porosimetry. The microporous nature of the skeletal and oolite grains appears to produce a softer material, which in turn increases the rock compressibility and decreases the expected seismic velocities of the samples.