The Change System

In PetroVR, any input on the part of the user that modifies the model is a change. No element of a model, either a whole model object such as a reservoir, or a single attribute of a variable, can exist without being reflected as a change or set thereof. A model, therefore, can be defined not only as a complex of objects and their attributes, but also as the history of inputs or changes that generated them.

Getting to know the Change System

Actions that in no way affect the model (such as moving a facility group on the Surface Layout) are not recorded, and so will not appear in the various tools for managing changes.

PetroVR records each and every change using a specific format, which can be reduced to this:

So, if you modify a well completion's reserves to 1 million barrels, what PetroVR will understand is that those reserves (the object) are instructed to receive a new value (the action).

Tthe object in this case is not the well completion itself, but only one of its attributes (the reserves), and that the information conveyed in the action is reduced to a minimum: something like "be 1 million barrels". Therefore, the specification of whose reserves we are talking about is contained in the object, and the whole change could be expressed thus:

Whenever PetroVR displays this change, it will normally appear thus:

Additional information is stored together with each change:

User: The user name under which the change was entered. This is by default the Windows user name, but can be changed by means of the Change User command in the Tools Menu.
Timestamp: Date and hour of the change. This is saved in change sets using the ISO 8601 standard and displayed using your Windows regional settings and local time.
Origin: File name of the project to which this change was originally applied. Only displayed when using the Browse Changes from File and Browse Recovery Log tools.

Changes are stored in two kinds of changes files, which include Changes files (.ch) proper, where sets of changes belonging to a single project are stored, and the Recovery Log, where all changes made in all projects are backed up.

The Change System has two main, complementary uses: on the one hand, it allows you to review in detail the building of a project, saving each separate step as a meaningful operation; on the other, it enables the possibility to apply these changes again, either in the same project or (by exporting them) in other projects.

This functionality is provided by several tools. Some of them are Change Browsers, which allow you to view, apply and save changes; they are Browse Unsaved Changes, Browse Saved Changes, Browse Changes from File and Browse Recovery Log. You can also load all the changes in one file directly using the Bulk Load from Changes File option in the Tools menu. Besides, you have the option to directly access changes made to a single variable (see Tracking Changes). Finally, the Scenarios and Decision Tree tools are based on the Change System and so offer options for browsing changes.

In some cases, it is not a single step but a complete set of them that makes sense and has to be applied as a single entity. An example of this could be first changing the value of an Input variable and then redefining it as a Function (see Input Modes); to recover the value change you must also reset it to the Input type again, so that the change will actually be made up of these two steps.