Human Resources allocation is a crucial factor for success in multi-project companies. It should consider the quantity of professionals needed to develop the project and the amount of time these professionals can dedicate to it. Companies where the core business is engineering design, software design or research and development projects, usually need a variety of specialists and the allocation of these workers on the projects can be done by a simulation of the process aiming to obtain better system performance. This work makes an analysis of sizing and allocation of human resources on design processes, proposing a simulation based method to improve it. An application to onshore oil well design process for a petroleum company was made, generating a model that represents the amount of professionals needed according to a given demand. After that, some scenarios were simulated aiming to improve the system performance metrics. Through the proposed method, the process was analyzed, identifying some bottlenecks and improvement points related to downsizing and deadline accomplishment. The simulated scenarios have shown that an organization modification through centralization of well engineering offices could reach these goals.