A Comparison of Model Calculations for Compressional Wave Velocity in Clastic and Carbonate Rocks

Compressional and shear wave velocity as well as their correlation are topic of different geoscientific fields and topic of many articles. Different approaches for vp and vs for fluid saturated porous rocks were published.This paper will show a comparison of different approaches for modelling vp for sandstone and carbonate samples and hence a comparison of calculated and measured values for dry and water saturated rocks. Starting point are two model types: the penny-shaped crack model by O’Connell and Budiansky and a long-wave first-order scattering theory by Kuster and Toksoez. After calculating vp for the dry rock with the two cited models, vp for the with brine saturated rocks is calculated using the theory by Gassmann.First data show that depending on the rock type different models are needed.O’Connell and Budiansky works good for both, carbonate and sandstone samples. Kuster and Toksoez gives only good results with the penny cracks.Using additional the fluid substitution equations by Gassmann gives good results and a good correlation with measured data.