Block 6 is Oman's largest and most significant oil and gas operation. The contract has operated under its current guise following signature of the renewed concession agreement in 1967, paving the way for the development of Oman's first crude oil reserves. The agreement to extract crude oil was signed with Shell, Total and Partex. The government backed into the concession in 1974 and the shareholders have remained unchanged since - Government of Oman (60%), Shell (34%), Total (4%) and Partex (2%). The concession only covers the extraction of crude oil and the use of associated gas for oilfield uses. Non-associated gas reserves (and condensates) belong exclusively to the government of Oman. PDO produced over 90% of Oman's gas in 2016 and will remain a major producer, despite the start-up of the Khazzan field in September 2017.