Land men can look at any county, it just cost money for them to drive to the other court house.
You can go to the county clerk office and look up records yourself. I'm sure they will show you were the books are, then you go to the section, township and range. They will not look it up for you as they are busy recording things, but usually they are more than helpful to show you where things are. Once you get to your legals, you will find leases, easement, deeds, etc. If the minerals were separated from the surface, you will need to look in different books. It's not hard.
Also, you can look up some thing on line at OK county records. com. Then for about $10 a month, you can open the records and for a small fee get copies off line. I'm sure how far back these counties have put on -line.