Distinguishing fluid injection induced ground deformation caused by fracture pressurization from porous medium pressurization

Ground deformation (both deformation patterns and deformation magnitudes) due to porous medium pressurization and fracture pressurization exhibits different characteristics. However, whether these differences can be detected during fluid storage is a complicated issue. Two analytical solutions have been previously developed to correlate ground deformation with underground fluid injection/extraction. One is Geertsma׳s (1973) solution on ground deformation associated with a disc-shaped reservoir (porous medium), and another is Sun׳s (1969) solution on ground deformation associated with a circular fracture. In this technique note, we compare these two solutions through a finite element modeling approach based on comparable boundary conditions, i.e., the similar areal extent, burial depth and fluid injection volume. We found that the deformation patterns are similar for these two cases on the ground surface, but very different underneath, especially in the horizontal direction. The radial extent of horizontal deformation is more restricted for the fracture pressurization case and more importantly, much higher magnitudes of ground deformation occur for the fracture pressurization case, which can provide new understanding of how to distinguish a fracture pressurization effect from porous medium pressurization.