The Bonan Block is a cluster of oil and gas fields in the southern part of the Bohai Gulf. CNOOC Ltd subdivides the fields into two groups the Bozhong 34 Fields and the Bonan Fields. Production from the block began in 1989 when Bozhong 28 1 was brought onstream. The Bozhong 34 2/4 fields were brought onstream the following year. The Bozhong 28 2S field and Bozhong 34 1N was brought onstream in March 2009 and December 2009 respectively.