Initiation and propagation of wormhole in unconsolidated rock matrix induced by long-term water injection

The initiation and propagation of wormhole near the wellbore during the process of water injection was investigated through finite element simulations. To describe the problem, a multi-physics coupling model, in which hydrodynamics, geomechanics and erosion were coupled, was built. By constructing a reservoir model with stochastic and inhomogeneous porosity this study found that the initial porosity plays an important role in the geometry and evolution direction of wormhole. The effects on the erosion rate and wormhole area under the consideration of parameters such as flow flux, erosion coefficient and pore pressure were elucidated. Furthermore, wellbore with multi-perforations was studied to investigate possible interactions between the perforations due to Darcy flow. The simulation results show that the wormhole is more likely to form around the longer perforations. With the increase of the angle between two perforations, the wormhole around the cusp of perforations is more likely to form while the wormhole around the wellbore is restrained. This work provides an insight to guide the design of perforation pattern and application of injection in terms of optimization of the hydrocarbon production.