Static and Dynamic Bulk Moduli of Deepwater Reservoir Sands: Influence of Pressure and Fluid Saturation

Abstract The static bulk modulus of unconsolidated sands is essential for predicting the in situ effective pressure to reduce drilling risks deepwater reservoirs; however, dynamic often more broadly available from seismic or well logging data. Therefore, it tempting investigate relationship between and moduli. We perform a series ultrasonic velocity measurements on 21 reservoir Gulf Mexico (GoM) study moduli simultaneously. Both room-dry brine-saturated velocities are measured under hydrostatic stress conditions derive Under conditions, if pore kept constant, volume change with confining can be monitored accurately by digital pump, which subsequently used estimate modulus. experimental results suggest that both decrease upon unloading. pressure-dependent modeled using Hertz-Mindlin contact theory at critical porosity combined modified Hashin-Shtrikman lower bound other porosities. theoretical estimates serve as upper static-to-dynamic ratio decreases value approaching 0.8 approximately 0.25 decreasing differential pressure. Moreover, effects brine saturation investigated Gassmann’s equation. substantially reduces difference moduli, making approach unity, may relevant rock properties.