A Scenario is a "What if?" or "Incremental" set of data that typically defines the options available to you. Many real world production problems that have any sort of production curtailment, or gas compression can only be analyzed using the combination of a "Base Scenario" and a "Incremental Scenario".

When you create a Project, it starts with a default “Base Scenario”, but you can add as many new scenarios as you require for your analysis.  Some economic data is stored a the Scenario level, and it is the default node for setting up your sales point (that is, the place at which your production is sold at a specified price).  Assets can be completely shared across scenarios so that data changes to that asset will be synchronized with the other versions of that asset that exist in the other scenarios.

A very common approach is to model your existing wells and facilities in a base scenario, then using the "Scenario" menu to copy the scenario and create an incremental development scenario that can be layered on top. From the "PlanView" tab, you can set your Scenario Consolidation Factors to establish what type of results will be reported at the Project level. For example, if Scenario A has a consolidation factor of +1 and Scenario B has a consolidation factor of -1, the project results will show the incremental results of Scenario A minus Scenario B.