Sand production is a common phenomenon in oil and gas reservoirs, which occurs when reservoir fluids exert a sufficient drag force on reservoir rocks to erode the matrix. Numerical models for sand production have been used to understand the sanding mechanisms and forecast sand-production potential of formations to design well completion, optimize production, and prevent setbacks in future operations. This paper presents a mathematical model for defining the conditions of sanding onset as well as to predict and quantify the sand rate. We also introduce fluid-flow coupling and a geomechanical and sand-production model. By using the proposed model and a set of experimental data, sanding-related variables are analyzed, and a matching process for the simulated results and forecast analysis are performed. The results show that elastoplastic constitutive models are indispensable, and a clear relationship exists between the sanding and plastic strains.