The provisions of this subchapter shall not apply to:
(1) gas produced from a common reservoir that contains both sweet and sour gas which was being lawfully used for the manufacture of carbon black under the provisions of the source law codified in Subchapters D and E of this chapter at the time of the passage of the source law for this section; or
(2) gas from gas wells located in these reservoirs which were entitled to be so used under the provisions of the source law codified in Subchapters D and E of this chapter at the time of the passage of the source law for this section.