The Material Balance is one of the basic techniques used to describe hydrocarbon reservoirs. No structural model is needed and no detailed descriptions of the reservoir features are required. All data will be on global or field level by averaging all reservoir parameters to be suitable for MB calculation. Consequently the results will be only on field level as well. Reservoir Simulation on the other hand is a more complex tool with a completely different workflow. The reservoir is represented in details and the high resolution results on well level and small sized block basis make the monitoring and management of the reservoirs possible. The results provide insight and understanding of the reservoir and can be used for future developing of the reservoir. In this Master thesis an approach is presented that integrates the MB methods in full field simulation modeling workflow as internal function or object, which makes MB applicable in reservoir simulation environment, utilizing grid models with full features and properties description as input data on well basis and cell by cell level. The new MB approach is able to be used at any stage of workflow matching the reservoir pressure and defining the Aquifer parameters or in prediction mode where different developing scenarios can be tested. The new concept is validated on a real field case. Based on the Elephant Oil Field belonging to ENI Oil Co the whole workflow including results is presented in form of a tutorial, as well.