OPM
Issue with difference cases if different time steps from original case
Think this is best explained by an example.
Say you have a case with these dates stored (here called "ORG")
01 Jan 2022 01 Jan 2023 01 Jan 2024
and two restarts from that case with the following dates (here called "RESTART_REF" and "RESTART_ALT") 01 Jan 2023 01 Jan 2024 01 Jan 2025 01 Jan 2026 01 Jan 2027
I then want to take a difference between these two cases in the 3D viewer.
If I select RESTART_REF as my main view, and select the difference case RESTART_ALT in the "Difference options", without selecting a "base time step", the difference behaves as expected, I subtract the same time step in RESTART_ALT from the selected time step for RESTART_REF in the main view. I can also select different time steps.
If on the other hand I select the case ORG in "Difference options" (and base time step as "disabled"), the case used to subtract ORG from the main case RESTART_REF is not matched on date, but rather on index in the list of existing time steps as far as I can see. E.g. if I in the main view for RESTART_REF have selected 01 Jan 2024, which is nr 2 in the list of time steps for that case, the date subtracted for the diff case is 01 Jan 2023 as that is the second time step in the list for ORG. This is confusing behavior.
If base time step is "disabled" the data for the two cases should be matched on the date/time by default and undefined if missing in one of them.
Thanks for the report.
A possible workaround for now is to use the "Import Eclipse Case (Time Step Filtered)" feature to make sure that all the cases you want to use in a difference operation has the same time steps loaded.
You can also select explicitly the right time step I think. My main worry is not the lack of workaround but that in some cases this behavior is not obvious and thus could lead to misinterpretation by users that assume the time steps used are matching.