This work examines the main sources, governing the international oil and gas operations around the world, with a view to examining whether we are witnessing the emergence of transnational petroleum law has emerged. The work explores the nature of governance in the petroleum industry and the extent to which the oil and gas industry is self-governed or governed by the state-made law. It assesses the degree of standardisation of governance to determine whether it is so high as to give rise to the emergence of lex petrolea. The main focus is on sources, specific to the oil and gas industry, such as: model contracts, industry usages, standards and guidelines promulgated by various industry organisations and associations. This work argues that lex petrolea is not yet a mature legal order. Its sources are best characterised as transnational layers of governance of the international exploration and production operations. As to the relationship between the alleged lex petrolea and the state-made law, it is demonstrated that the two are vitally important to and mutually dependent on each other.