Mineral rights owner

I recently got a letter in regards to my grandfather owning mineral rights in Oklahoma. Letter stated there has been 2 well drilled and completed. Also letter stated there was bonus and royalty money to be claimed. I was wondering if that means oil is already being pumped and how would I find out how much. I don’t have much knowledge about this matter other than in inherited the mineral rights. Thank you

More info is needed for someone to help you. Who was the letter from? Did it identify in whose name the mineral rights are currently in? How were you located to receive the letter? What are the legals - section, township and range? What entity is holding bonus and royalty $? The more details you are willing to share, the more likely you will get good help.

What County and the legal description?