Wellbore instability induced by alternating water injection and well washing with an elasto-plastic erosion model

The well instability induced by well washing was investigated with finite element simulations. To describe this problem, a multi-physics coupling model, in which hydrodynamics, geomechanics and erosion were coupled through Young modulus, flow velocity and plastic yield, was established. We built a series of model to simulate this process. Results show that rock around wellbore and the cusp of perforation can be damaged in the process of well washing. This damage accelerates the erosion and the erosion induces further new damage. With the decrease of well washing pressure, the damage area increases. Some suggestions were given to prevent the wellbore instability such as injection with clean water, reinforcing the cement sheath and increasing well washing pressure. Our work could provide an insight in guiding the design of stable wellbore and well washing procedure.