You will need to have someone search the deed records in that county under names of your ancestors to see if there is a deed or other conveyance of mineral rights to them, or you can do that yourself. For a small fee, many title companies will do a names search, and give you a list of documents in the deed records under whatever name(s) you provide them.
Sixty-five counties are available through OkCountyRecords and it is possible to do a remedial name search through that link. Twelve counties listed below must be searched individually: