My condolences to you and your family.
If you have probate documents, did they list the mineral rights with descriptions? If not, there are several ways to get started.
I would start with looking in www.okcountyrecords.com under your grandparents’ names. It may not go back far enough, but it might. It is free to look and only costs a few dollars to print. You want to find the minerals tracts. You may have more tracts than what is currently producing. Remember that you need to file your names and addresses with the title info in the counties where you have minerals. You also have to contact every operator and file a title change, plus ask what they need to put you into pay status.
The OK tax site will tell you is a well is active and what the production is. https://oktap.tax.ok.gov/oktap/web/_/. You do not need a login. Go to the HELP box and use the PUN lookup. Use the well name if you know it or the bottom hole location or surface location.
The OCC will give the basics on the well filings. Well activity: Test.
See if you can find any checkstubs or deeds or any paperwork in your inherited boxes.