This is a process whereby, for a given scenario,  an input assumption (or assumptions) are changed and the result of that change on the output is calculated. Typical sensitivity variables are commodity price, capital cost, operating cost, production rate, reserves. There are 2 distinct variants of sensitivity analysis used for different purposes: Static Sensitivity Analysis:  In this case, the sensitivity analysis will change the value of an input parameter (or parameters) and recalculate results, altering neither underlying project selections nor project timing (while acknowledging that the sensitivity may cause some wells and projects to be removed from the results if they become uneconomic or their economic limit is reached at a different time).  In this case, the sensitivity analysis will take the project timing as fixed and not alter it.  Since project timing is essentially a primary constraint in “Static” mode, there is no guarantee that other constraints will not be violated in this mode. This type of analysis is used for generation of tornado charts and for assessing the relative sensitivity of a final plan to various input factors. Compared to “Dynamic Sensitivity”, it can result in less precise results. Dynamic Sensitivity Analysis:  In this case, the sensitivity analysis will change the value of an input parameter (or parameters) and recalculate results, altering project timing as indicated.  Project timing shifts may be indicated based upon the sensitivity variables affecting the constraints, or from changes to economic limits in the case of dependent operations (like up hole recompletions).  As in the static case, this sensitivity may cause some wells and projects to be removed from the results if they become uneconomic or their economic limit is reached at a different time.    This type of analysis is commonly used when performing a variance analysis with a simulation or portfolio tool. Compared to “Static Sensitivity”, it will be more likely to honor preexisting constraints and may yield a more precise result. The reader might observe some overlap between a scenario and a dynamic sensitivity, since they may result in a unique “what and when”.  The distinction is that sensitivities (whether they be static or dynamic) are always related to, and generated based upon, a specific scenario.