Tex. Nat. Res. Code § 87.092

In any common reservoir in this state producing both sweet and sour gas, no person may operate a plant for the extraction of the natural gasoline content of gas in which sweet gas and sour gas are commingled, or plant casinghead gas is commingled with either sweet gas or sour gas or both, until the person secures from the commission a permit authorizing the operation of the plant.