Comparing Ultra Sonic Velocities from the Upper and Lower Cretaceous from the North Sea

Ultra sonic velocities are measured in the elastic regime during geomechanics measurements on plugs from the Upper and Lower Cretaceous chalk formations in the North Sea. The p-wave velocities are compared to data from similar studies where the effect of the cleaning, stress state, saturating fluid, degree of saturation and clay content are evaluated as contributors to the measured velocity. A clear difference is seen in the p-wave velocity where the velocity from the Upper Cretaceous is seen to be significantly higher than the velocity of the Lower Cretaceous at comparable porosities.