Have you tried www.okcountyrecords.com? Use the name of the relative and search for leases there. All leases are filed for the counties they track. You have quite a few to begin with. You may discover others.
Then go to the OTC tax site to see if there are producing wells. You can search by the section or quarter section. You are owed royalties if your description is within the spacing unit of the well.
You can find the spacing orders using the http://www.occeweb.com/caseprocessingonline/default.aspx