Promulgated by the Federal Military Government of Yakubu Gowon on 27 November 1969 — mid-civil-war, three months before Biafra's surrender — to consolidate three separate colonial statutes (the Mineral Oils Ordinance 1914, the Mineral Oils (Amendment) Act 1959, and the Petroleum Profits Tax Ordinance 1959) into a single sovereign regime. Section 1(1) reads: 'The entire ownership and control of all petroleum in, under or upon any lands to which this section applies shall be vested in the State' — applying to all Nigerian territory and the continental shelf. This is the first fully Nigerian assertion of sovereign ownership of petroleum, replacing the colonial Crown-ownership formula and extinguishing any private mineral claim, including the residual corporate claim under the 1899 99-year Royal Niger Company mineral royalty deed whose Northern zone overlapped some of the southern oilfields.
The Act created three licence types — Oil Exploration Licence (OEL, 1 year), Oil Prospecting Licence (OPL, 5 years), and Oil Mining Lease (OML, 20 years) — granted by the Minister of Petroleum Resources. Section 6 reserved licences to Nigerian citizens or companies incorporated in Nigeria but with ministerial discretion to grant to foreign companies; that became the basis of the Joint Venture and Production Sharing Contracts with Shell, Mobil, Chevron, Elf, Agip and Texaco through the 1970s–2010s. The First and Second Schedules set out the royalty rates (originally 12.5% onshore, 8% offshore beyond 100m water depth) — the operative numbers behind every Niger Delta agitation about derivation revenue for the next 50 years.
The Act remained in force, lightly amended, until repealed by the Petroleum Industry Act 2021. Together with the Land Use Act 1978 (sub-surface rights) and the Constitution s.44(3) (vesting mineral revenue in the Federation), the 1969 Petroleum Act is the legal trinity that made oil a federal — not regional, not community — resource. The political consequence: every barrel of crude lifted from Bayelsa, Rivers, Delta or Akwa Ibom from 1970 onwards belonged, in law, to Abuja.