Okla. Stat. tit. 52 § 56
Every corporation, joint-stock company, partnership or person, engaged in the business of carrying or transporting crude oil or petroleum or any of the products thereof for hire or otherwise, by pipeline, within this state, and by virtue of and in conformity to, any valid law incapable of revocation by any laws of this state or of the United States, or by virtue of and in conformity to the provisions of this article, shall be deemed a common carrier thereof as at common law and no such common carrier shall allow or be guilty of any unjust or unlawful discrimination, directly or indirectly, in favor of the carriage, transportation, storage or delivery of any crude, stock or storage oil, or any products thereof, in its possession or control, or in which it may be interested, directly or indirectly.
Okla. Stat. tit. 52, § 56