CNOOC Limited Completes Acquisition of Nexen Inc.

(Hong Kong, 26 February, 2013) - CNOOC Limited (the "Company", NYSE: CEO, SEHK: 00883) announced today that it has completed its acquisition of Nexen Inc. ("Nexen"). Total consideration of approximately US$15.1 billion has been paid for Nexen's common and preferred shares.

Mr. Wang Yilin, Chairman of CNOOC Limited said, "The Company is delighted to acquire a leading international platform through the acquisition of Nexen. We strongly believe that this acquisition is a good strategic fit for us and will create long-term value for our shareholders."

Mr. Li Fanrong, Chief Executive Officer of the Company commented, "Nexen is a strong, diverse company with attractive growth prospects, a large resource and reserve base, high potential exploration prospects, and high quality talented employees capable of extracting the value of these assets. We will thoroughly utilize the platform it provides to further our overseas business. "

Nexen will operate as a wholly-owned subsidiary of CNOOC Limited, and will continue to be led by CEO, Kevin Reinhart, who has been with Nexen for over 18 years. A new Board of Directors comprised of CNOOC Limited, existing Nexen management and Canadian independent directors has been established, with Mr. Li Fanrong as Chairman of the Board.

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Notes to Editors:

More information about the Company is available at http://www.cnoocltd.com.

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This press release includes "forward-looking statements" within the meaning of the United States Private Securities Litigation Reform Act of 1995, including statements regarding expected future events, business prospectus or financial results. The words "believe", "intend", "expect", "anticipate", "project", "estimate", "plan", "predict" and similar expressions are intended to identify such forward-looking statements. These statements are based on assumptions and analysis made by the Company in light of its experience and perception of historical trends, current conditions and expected future developments, as well as other factors that the Company believes reasonable under the circumstances. However, whether actual results and developments will meet the Company's expectations and predictions depends on a number of risks and uncertainties which could cause the actual results, performance and financial conditions to differ materially from the Company's expectations, including those associated with fluctuations in crude oil and natural gas prices, the exploration or development activities, the capital expenditure requirements, the business strategy, the highly competitive nature of the oil and natural gas industries, the foreign operations, environmental liabilities and compliance requirements, and economic and political conditions in the People's Republic of China. For a description of these and other risks and uncertainties, please see the documents the Company has filed from time to time with the United States Securities and Exchange Commission, including 2011 Annual Report on Form 20-F filed on April 20, 2012.

Consequently, all of the forward-looking statements made in this press release are qualified by these cautionary statements. The Company cannot assure that the actual results or developments anticipated will be realized or, even if substantially realized, that they will have the expected effect on the Company, its business or operations.

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For further enquiries, please contact:
Ms. Michelle Zhang
Deputy Manager, Media/Public Relations
CNOOC Limited
Tel: +86-10-8452-6642
Fax: +86-10-8452-1441
E-mail: MR@cnooc.com.cn

Ms. Angela Hui
Ketchum Newscan Public Relations Ltd
Tel: +852-3141-8091
Fax: +852-2510-8199
E-mail: angela.hui@knprhk.com

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