Fluid Flow Induced by Seismic Waves in Fractures

Youcef Bouzidi, Nabil Kharoua , Fateh Bouchaala , Hamid Ait Abderahmane, Douglas Schmitt

A theoretical and numerical analysis is presented on the squeezed film of an incompressible fluid between two parallel fracture walls induced by seismic waves at normal incidence. In the frame of small oscillations, a closed form of the fluid pressure changes along with the fracture, and the fluid velocity field distribution is proposed. The developed analytical solutions are valid for any relative amplitude and phase of the vibrations within the assumed small oscillations and can help in understanding the induced fluid flow in fractures near zero-offset seismic wave propagation in a fluid-saturated fractured reservoir with nearly parallel fracture walls. It is found that the fluid flow is governed by the squeezing motion due solely to the difference of the vertical fluid velocities. In the absence of experimental data, the analytical solutions are validated with numerical solutions of the full Navier-Stokes equations. The comparison confirms the accuracy of the analytical solutions, showing that average fracture pressure rises with frequency, fracture length squared, and decreasing wall separation. It is also found that the presence of a pressure gradient does not hinder the overall flow during an oscillation cycle. The high induced horizontal acceleration of the fluid can reduce surface tension and improve oil to dissolve in any injected solvents. This may help mobilize fluids in fractured reservoirs, potentially explaining the improved oil recovery observed with surface seismic wave stimulation near production wells. Optimizing flow parameters through accurate fracture characterization can further enhance oil recovery.