Abstract: The propagation of pressure wave of unsteady flow of elastic fluid in low permeability reservoirs is researched using the steady state replacement method. Among the different percolation processes such as planoparallel flow, planoradial flow and spherical centripetal flow, the pressure wave propagating velocity is the fastest under the spherical centripetal flow, and the slowest under the planoparallel flow. And low permeability reservoir is slower than mid-high permeability reservoir in pressure wave propagating velocity.

Key words: low permeability, pressure, travel time, percolation