Interaction of Low-Frequency Tube Waves with Poroelastic Reservoirs Containing Perforations

Tube or Stoneley wave is known to strongly interact at low frequencies with poroelastic formations provided that flow is not restricted at the borehole-formation interface. Increased permeability leads to increased attenuation and decreased velocity of the tube wave. In this study we focus on reflection of low-frequency tube waves from various finite-size poroelastic structures. First, we examine a model of a thin reservoir and demonstrate good applicability of the approximate 1D effective wavenumber approach to describe interaction of tube waves with porous formations. We confirm that higher permeability leads to higher reflection coefficient. Then we analyze model of an idealized (disk-shaped) perforation inside a poroelastic layer and show that it has higher reflectivity compared to washout zone of the same geometry but with no-flow conditions at the face.