The Nigerian National Petroleum Corporation (NNPC) is the state oil corporation which was established on April 1, 1977. In addition to its exploration activities, the Corporation was given powers and operational interests in refining, petrochemicals and products transportation as well as marketing. Between 1978 and 1989, NNPC constructed refineries in Warri, Kaduna and Port Harcourt and took over the 35,000-barrel Shell Refinery established in Port Harcourt in 1965. In 1988, the NNPC was commercialised into 12 strategic business units, covering the entire spectrum of oil industry operations: exploration and production, gas development, refining, distribution, petrochemicals, engineering, and commercial investments. Currently, the subsidiary companies include: Nigerian Petroleum Development Company (NPDC) The Nigerian Gas Company (NGC) The Products and Pipelines Marketing Company (PPMC) Integrated Data Services Limited (IDSL) National Engineering and Technical Company Limited (NETCO) Hydrocarbon Services Nigeria Limited (HYSON) Warri Refinery and Petrochemical Co. Limited (WRPC) Kaduna Refinery and Petrochemical Co. Limited (KRPC) Port Harcourt Refining Co. Limited (PHRC) NNPC Retail Duke Oil