[(Incorporated in Hong Kong with limited liability under the Companies Ordinance) ) (Stock Code: 883 DATE OF BOARD MEETING Board Company The board of directors (the " By Order of the Board CNOOC Limited Zhong Hua Joint Company Secretary Hong Kong, 8 August 2012 As at the date of this announcement, the Board comprises: Executive Directors Li Fanrong Wu Guangqi]

[THIS CIRCULAR IS IMPORTANT AND REQUIRES YOUR IMMEDIATE ATTENTION If you are in any doubt If you have sold or transferred (Incorporated in Hong Kong with limited liability under the Companies Ordinance) (Stock Code: 00883) CONNECTED TRANSACTION RELATING TO THE COALBED METHANE RESOURCES EXPLORATION AND DEVELOPMENT COOPERATION AGREEMENT Independent Financial Adviser to the Independent Board Committee SOMERLY LIMITED A notice] [(Incorporated in Hong Kong with limited liability under the Companies Ordinance) (Stock Code: 00883) NOTICE OF EXTRAORDINARY GENERAL MEETING NOTICE IS HEREBY GIVEN “ ” ORDINARY RESOLUTION “ THAT ” By Order of the Board CNOOC Limited Zhong Hua Joint Company Secretary Hong Kong, 3 August 2012 Registered Office: 65th Floor, Bank of China Tower 1 Garden Road Hong Kong] [(Incorporated in Hong Kong with limited liability under the Companies Ordinance) (Stock Code: 00883) Form of proxy for the Extraordinary General Meeting to be held on 21 August 2012 I/We (Note 1) of being the registered holder(s) of shares (Note 2) of HK$0.02 each in the share capital of the above-named Company HEREBY APPOINT THE CHAIRMAN OF THE MEETING (Note]

[CNOOC Limited]

[CNOOC Limited]

[CNOOC Limited]