This thesis focuses on serious games that simulate realistic situations. The objectives of such games go beyond mere entertainment to fields such as training, for example. Since other areas of Computer Science provide methods and tools for simulating and reasoning about real situations, it is highly desirable to use them in this kind of serious games. This thesis introduces a new framework on which simulation techniques from different areas, such as modeling and simulation, geographic information systems and multi-agent systems, can be integrated into a serious game architecture. The proposed solution resulted in the conception of a novel simulation modeling paradigm, named process-oriented simulation (POS), which combines different aspects of the more traditional object-oriented simulation (OOS) and agent-oriented simulation (AOS) paradigms. The main idea of POS is the separation between state and behavior of the entities involved in the simulation. This characteristic favours the modularization of complex behaviors and the integration of different and interfering simulation models into a single simulation. Based on the POS paradigm, a discrete-event simulation formalism named Process-DEVS was developed as an extension of the well-known DEVS simulation formalism. Some formalisms, such as workflows and cell space processes, were mapped to Process-DEVS and tested in the implementation of two systems: an emergency training game and a contingency planning system, both designed for the oil and gas industry.