An acoustic modeling method with possible application to enhanced hydrocarbon reservoir characterization is presented. The method involves numerical simulation of two-dimensional (2-D), low-frequency transient acoustic-wave propagation in porous media and is based on the explicit finite-difference formulation of Biot's system of equations in a fluid-saturated poroacoustic medium. The scheme is second-order accurate in space and time.Synthetic seismograms computed using this approach indicate that transient acoustic-wave propagation in unbounded fluid-filled porous media and in the presence of fluid viscosity closely mimics that in an equivalent nonporous (single-phase) solid. However, in the presence of heterogeneities, such as layering, inclusions, and discontinuities, the results show that acoustic-wave characteristics are affected by spatial variations in reservoir parameters such as porosity, permeability, and fluid content as well as the fluid-solid interaction. The effects of permeability and fluid viscosity are discernible in dispersion and dissipation of the compressional wave, whereas porosity affects the compressional velocity as well. The results of this study suggest that no equivalent single-phase model can adequately describe the effects of permeability and porosity on seismic waves propagating through heterogeneous fluid-filled porous media.