SALE, PURCHASE, DELIVERY, AND RECEIPT OF GAS.
Tex. NAT. RES Code § 91.058.
in effect(a) Each sale, purchase, delivery, and receipt of gas by volume made in this state by, for, or on behalf of an oil and gas lease owner, royalty owner under a lease, or other mineral interest owner shall be made and the gas shall be measured, calculated, purchased, delivered, and accounted for on the basis of a standard cubic foot of gas as defined in this subchapter and determined under this subchapter.
(b) If the provisions of this subchapter operate to change the basis of measurement provided in existing contracts, the price for gas, including royalty gas, provided for in the contracts shall be adjusted to compensate for the change in the method of measuring the volume of gas delivered under the contracts if either the purchaser or seller so desires.
(c) This section is intended to protect parties to contracts in existence on October 4, 1949, so that the total amount of money paid for a volume of gas purchased or required to be accounted for under these contracts shall remain unaffected by this subchapter.