Acoustics simulation and analysis of three phase fluid patchy saturations porous rock

Abstract

Fluid saturation distribution is patchy due to variation of lithology, porosity and permeability of porous rock. Traditional porous medium theory based on homogeneous saturation does not apply to acoustical signatures calculation of patchy saturation porous medium. Employing three phase fluid Brooks-Corey model, Gassmann theory and bound theory, acoustical signatures calculation method of mesoscopic-scale inhomogeneous porous rock with three phase fluid patchy saturation is proposed, in order to research the effect of fluid saturation distribution on acoustical signatures of rock. Under conditions of capillary equilibrium, the quantitative relationship between porous medium acoustical signatures and global water saturation is established, then rules of compressional wave velocity ( V p) and shear wave velocity ( V s) of different fluid saturated rock vary with different global water saturation are revealed. Numerical results demonstrate that V p of porous rock with three phase fluid patchy saturations more continuous variation across the entire global water saturation range. It will be more suitable for quantitative interpretation of hydrocarbon saturations than the case of three phase fluid homogeneous saturations. V s of porous rock doesn’t depend on saturations distribution. However, the relationship between V s and global water saturation in three phase fluid saturations porous rock is more complex than that in two phase fluid saturations porous rock.