Density/Porosity Versus Velocity of Overconsolidated Sands Derived from Experimental Compaction

We present P- and S-wave velocities and density/porosity of seven natural sands experimentally mechanically compacted in various loading and unloading stages. The results show different velocity-density/porosity relationships for overconsolidated stages compared to normally consolidated stages at the same stress level. We utilised different rock physics models to observe the data on velocity-density/porosity and VP/Vs versus acoustic impedance crossplots. The velocity-porosity plot from overconsolidated sands plotted along the friable sand lines not only describe sorting deterioration but also differences in preconsolidation stresses. Well logs data from the Barents Sea show similar patterns to the measured data. The VP/VS versus acoustic impedance crossplot shows two additional trends (e.g. in the direction of reduced stress and increased precompaction stress). Fluid sensitivity is low in overconsolidated sands compared to normal consolidated sands as a function of increasing preconsolidation stress. These findings allow us better rock physics diagnostics of uplifted sediments and application of 4D seismic monitoring of uplifted basin like in the Basents Sea.