Modelling of seismic wave propagation in heterogeneous poroelastic media using a high-order staggered finite-dilfference method

Hydrocarbon reservoirs are composite multiphase media with gas and/or liquid contained in voids between solid grains. In this work, instead of using the velocity-stress finite-difference scheme of fourth-order in space and second order in time, we propose an improved explicit eighth-order staggered finite-difference algorithm in space and second order in time for poroelastic media to enhance the computation efficiency. Although the time step is a little smaller than that in fourth-order, the high-order FD scheme can use much coarser grids than that for the fourth-order. This feature compensates its inefficiency in time domain. Using this scheme, we calculate the snapshots and time series on a two-layered model. We also simulate the wave propagation in equivalent elastic and poroelastic models. Slow waves and their effects are clearly seen. Our numerical modeling shows that, although slow waves are attenuated strongly, when they are reflected by an interface, the converted P- and shear waves propagate in a normal way with much less attenuation than the slow waves.