UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

Report of Foreign Private Issuer

Pursuant to Rule 13a-16 or 15d-16 

of the Securities Exchange Act of 1934

For the month of June 2020

Commission File Number 1-14966

CNOOC Limited

(Translation of registrant’s name into English)

65th Floor

Bank of China Tower

One Garden Road

Central, Hong Kong

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F x    Form 40-F ¨ 

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ¨

Indicate by check mark whether by furnishing the information contained in this Form, the registrant is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes ¨    No x

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): Not applicable

Signature

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: June 11, 2020

EXHIBIT INDEX

Exhibit 99.1

中國海洋石油有限公司 

CNOOC LIMITED

For Immediate Release

CNOOC Limited Announces  

Qinhuangdao 33-1S Oilfield Phase I Project  

Commences Production

(Hong Kong, June 11, 2020) - CNOOC Limited (the “Company”, SEHK: 00883, NYSE: CEO, TSX: CNU) announced today that Qinhuangdao 33-1S oilfield phase I project has commenced production.

Qinhuangdao 33-1S oilfield is located in central and western Bohai with an average water depth of 21 meters. The project has built one wellhead platform in addition to fully utilizing the existing facilities of Qinhuangdao 33-1 oilfield and Qinhuangdao 32-6 oilfield. A total of 13 producing wells are planned, including 9 production wells and 4 water injection wells. The project is expected to reach its peak production of approximately 6,000 barrels of crude oil per day in 2021.

CNOOC Limited holds 100% interest of Qinhuangdao 33-1S oilfield and acts as the operator.

- End -

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 “expect”, “anticipate”, “continue”, “estimate”, “objective”, “ongoing”, “may”, “will”, “project”, “should”, “believe”, “plans”, “intends” and similar expressions are intended to identify such forward-looking statements. These statements are based on assumptions and analyses made by the Company in light of its experience and its perception of historical trends, current conditions and expected future developments, as well as other factors the Company believes are appropriate under the circumstances. However, whether actual results and developments will meet the expectations and predictions of the Company depends on a number of risks and uncertainties which could cause the actual results, performance and financial condition to differ materially from the Company’s expectations, including but not limited to those associated with fluctuations in crude oil and natural gas prices, macro-political and economic factors, changes in the tax and fiscal regimes of the host countries in which we operate, the highly competitive nature of the oil and natural gas industry, the exploration and development activities, mergers, acquisitions and divestments activities, environmental responsibility and compliance requirements, foreign operations and cyber system attacks.  For a description of these and other risks and uncertainties, please see the documents the Company files from time to time with the United States Securities and Exchange Commission, including the Annual Report on Form 20-F filed in April of the latest fiscal year.

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

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For further enquiries, please contact:

Ms. Jing Liu 

Manager, Media & Public Relations 

CNOOC Limited 

Tel: +86-10-8452-3404 

Fax: +86-10-8452-1441

E-mail: mr@cnooc.com.cn

Ms. Ada Leung

Hill+Knowlton Strategies Asia

Tel: +852-2894-6225

Fax: +852-2576-1990

E-mail: CNOOC@hkstrategies.com