Petroleum exploration offshore Sierra Leone commenced between the 1970s and 1980s on shallow continental shelf. Exploratory wells drilled over the period penetrated significant thicknesses of reservoir quality sandstones ranging in age from mid-Jurassic to mid-Cretaceous. These exploration efforts were halted despite evidence of key hydrocarbon indicators, probably because of deep water economics, technology and distance from mature source rocks. In 2001 the Parliament of Sierra Leone promulgated the new Petroleum Exploration and Production Act which established the Petroleum Resources Unit (PRU), with powers to regulate petroleum exploration activities in the country. In 2000 – 2001, TGS-NOPEC acquired 5,800 line kilometers of 2D seismic offshore Sierra Leone. The area was divided into seven bocks, each of approximately 4,500sq km. Following a bid round in 2003, four of the seven blocks were awarded to three companies. Further awards were subsequently made through direct negotiations and agreements between government and the companies. In 2008, the Petroleum Resources Unit created three additional blocks. Though exploration activities by the companies have been slow, one has advanced its exploration effort to the identification of petroleum prospects in one of its blocks. Drilling of one of these prospects in 2009 has led to the discovery of petroleum. The announcement of this find together with the discovery of petroleum in neighbouring Ghana, has led to renewed interest in Sierra Leone by petroleum companies.