How To Determine If There Is A Mineral Lease On A Property

I inherited an interest in some property in Andrews County, Texas. I pay real property taxes but no mineral lease property taxes. The interest involves Block A-43, Section 5 E/2. The last know oil companies involved in three wells on the property was Phillips and Exxon back in the 1980’s. How can I find out if these two companies still have a mineral lease on this 320 acres? Thanks for any help.

Just by looking at it I'm assuming the whole thing is held by the NORTHEAST FUHRMAN-MASCHO UNIT. If it is, I doubt it'll ever come open again. Unfortunate!