[FORM 20-F (Mark One) ¨ OR ý For the fiscal year ended December 31, 2014 OR ¨ For the transition period from _________________ to _______________ OR ¨ Date of event requiring this shell company report CNOOC LIMITED N/A Hong Kong (Jurisdiction of incorporation or organization) 65th Floor, Bank of China Tower One Garden Road, Central Hong Kong Hua Zhong th] [China National Offshore Oil Corporation and CNOOC Limited Framework Agreement in respect of the Connected Transactions Table of Contents 1. Scope of Products and Services 2. Transaction Principles 3. Pricing Principles 4. Mode of Operations 6. Term and Termination of the specific Product and Service Contracts 8. Performance of this Agreement 9. Force Majeure 10. Announcement 11. Miscellaneous 12. Notices] [Subsidiaries As of December 31, 2014, we owned, directly or indirectly, the following subsidiaries. Name of entity Our interest Jurisdiction of incorporation CNOOC China Limited 100% Tianjin, PRC CNOOC International Limited 100% British Virgin Islands China Offshore Oil (Singapore) International Pte Ltd 100% Singapore CNOOC Finance (2003) Limited 100% British Virgin Islands Malacca Petroleum Limited 100% Bermuda OOGC America LLC] [CNOOC Limited (incorporated under laws of Hong Kong with limited liability) Code of Ethics for Directors and Senior Officers 28 August 2014 I. INTRODUCTION Each of the directors and Senior Officers has the responsibility to obey the law and act honestly and ethically. To that end, this Code of Ethics is a guide intended to assist each of the directors] [CERTIFICATIONS I, Fanrong Li, certify that: 1. I have reviewed this annual report on Form 20-F of CNOOC Limited; 2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made,] [CERTIFICATIONS I, Hua Zhong, certify that: 1. I have reviewed this annual report on Form 20-F of CNOOC Limited; 2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made,] [CERTIFICATIONS Fanrong Li, the Chief Executive Officer and Hua Zhong, the Chief Financial Officer of CNOOC Limited, each certifies that, to the best of his knowledge: 1. the Report fully complies with the requirements of Section 13(a) or 15(d) of the Exchange Act; and 2. the information contained in the Report fairly presents, in all material respects, the financial condition] [CNOOC LIMITED Estimated Future Reserves and Income Attributable to Certain Leasehold Interests and Derived Through Certain Production Sharing Contracts SEC Parameters As of December 31, 2014 \s\ Herman G. Acuna \s\ Eric T. Nelson Herman G. Acuna, P.E. Eric T. Nelson, P.E. TBPE License No. 92254 TBPE License No. 102286 Managing Senior Vice President – International Senior Vice President [SEAL]] [INDEPENDENT LETTER , THE GREATER ANGOSTURA FIELDS BLOCK 2C, TRINIDAD & TOBAGO ESTIMATED PROVED RESERVES AND FINANCIAL DATA, BASED ON SEC RULES Prepared for CNOOC LIMITED st As at 31 , February GAFFNEY, CLINE & ASSOCIATES (CONSULTANTS) PTE LTD This summary letter is based on Gaffney, Cline & Associates’ official report and has been provided at the request of CNOOC] [Exnibit 15.3 H L & N G R R Y E 2014 D A F E Cerro P C K K Escondida, A A and and B Caipipendi in Prepared For: CNOOC LIMITED , January Victor Wayne Taylor Texas, USA PE License# 71417 Principal Engineer RPS Reserve Audit Report YE 2014 RESERVE LETTER RPS Reserve Audit Report YE 2014 411] [February 28, 2015 CNOOC Limited No. 25, ChaoYangMenBei Dajie DongCheng District Beijing 100010 China Gentlemen: The properties subjected to the procedural audit by Ryder Scott account for a portion of CNOOC’s total net proved the procedural audit conducted by Ryder Scott addresses the following percentage of the total proved reserves of CNOOC as summarized in the following table: Reserves Categories] [February 28, 2015 CNOOC Limited c/o Nexen Energy ULC th 801 – 7 Calgary, Alberta T2P 3P7 Re: Gentlemen: audit of CNOOC Limited’s (“CNOOC”) proved synthetic crude oil and bitumen reserves, as of Reserves included herein are expressed as reserves as represented by CNOOC. Gross reserves are defined as the total estimated petroleum to be produced from these properties after] [DeGolyer and MacNaughton 5001 Spring Valley Road Suite 800 East Dallas, Texas 75244 February 28, 2015 CNOOC Limited c/o Nexen Energy ULC 801-7 th Avenue S.W Calgary, AB T2P 3P7 Gentlemen: equivalent barrel basis as estimates have been prepared in of December 31, 2014, and that its reserves Reserves included herein are expressed as reserves as represented by CNOOC. Gross] [CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM Hong Kong April 22, 2015] [CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM We consent to the incorporation by reference in the Registration Statement on Form F-3 (File No. 333-187114) and the Post-Effective Amendment No.1 to the Registration Statement on Form F-3 (File No. 333-188261) of our reports dated March 27, 2015 relating to the consolidated financial statements of CNOOC Limited and its subsidiaries as of] [[LETTERHEAD OF RYDER SCOTT COMPANY, L.P.] Consent of Independent Consultant Ryder Scott Company, L.P. TBPE Firm Registration No. F-1580 Houston, Texas April 21, 2015] [[LETTERHEAD OF GAFFNEY, CLINE & ASSOCIATES (CONSULTANTS)PTE LTD.] YDH/dh/PS-13-2127&PS-13-2128/2014/L0090a nd 22 CNOOC Limited No. 25, Chaoyangmenbei Dajie Dongcheng District Beijing 100010, P.R. China Dear Sir, Consent of Independent Consultant Yours sincerely, G AFFNEY, C LINE & ASSOCIATES ( C ONSULTANTS ) P TE LTD Stephen M. Lane Technical Director] [Consent of RPS Debbie Perkins Vice President Houston, Texas March 31, 2015] [[LETTERHEAD OF MCDANIEL & ASSOCIATES CONSULTANTS LTD.] Consent of Independent Consultant MCDANIEL & ASSOCIATES CONSULTANTS LTD. P. A. Welch, P. Eng. President & Managing Director McDaniel & Associates Consultants Ltd. 2200, Bow Valley Square 3, 255 - 5 Avenue S.W. Calgary, Alberta, T2P 3G6 Canada April 22, 2015] [[LETTERHEAD OF DEGOLYER AND MACNAUGHTON] Consent of DeGolyer and MacNaughton DeGolyer and MacNaughton Texas Registered Engineering Firm F-716 Dallas, Texas April 22, 2015]