I am very much agree with Temr. To become good simulation engineer you have to know Petrel G&G in details otherwise you are unable to use Petrel RE properly. There are many things in Petrel RE where it is linked with Petrel G&G. During upscaling of the model if you have no idea of propery modeling, your upscaled model will give different picture. With my little experience I can say that Petrel/Petrel RE is the ultimate tool for present day reservoir modeling.
Thanks