Tex. Natural Resources Code § 52.172

The owner of said land is hereby authorized to sell or lease to any person, firm, or corporation the oil and gas that may be thereon or therein upon such terms and conditions as such owner may deem best, subject only to the provisions hereof, and he may have a second lien thereon to secure the payment of any sum due him. All leases and sales so made shall be assignable. No oil or gas rights shall be sold or leased hereunder for a delay rental during the primary term of less than 10 cents per acre per year plus royalty, and in case of production, the lessee or purchaser shall pay the state the undivided one-sixteenth of the value of the oil and gas reserved herein, and like amounts to the owner of the soil.