[] [CNOOC LIMITED Debt Securities Underwriting Agreement Standard Provisions Guarantor Underwriting Agreement Securities Underwriters Representative Issuer Agreement Trustee From time to time, CNOOC Limited, a company incorporated with limited liability under the laws of Hong Kong (the “ Registration Statement Commission Securities Act Basic Prospectus Prospectus Supplement Rule 430 Information Registration Statement Prospectus Preliminary Prospectus supplement amendment amend Exchange Act Effective] [INDENTURE Dated as of , 2013 Among CNOOC FINANCE (2013) LIMITED as Issuer CNOOC LIMITED as Guarantor THE BANK OF NEW YORK MELLON as Trustee THE BANK OF NEW YORK MELLON as Paying Agent and THE BANK OF NEW YORK MELLON as Registrar DEBT SECURITIES TABLE OF CONTENTS Page ARTICLE I DEFINITIONS Section 1.01 Definitions 1 Section 1.02 Rules of] [[LETTERHEAD OF DAVIS POLK & WARDWELL LLP] May 1, 2013 CNOOC Limited 65th Floor, Bank of China Tower One Garden Road, Central Hong Kong CNOOC Finance (2013) Limited c/o Intertrust Corporate Services (BVI) Limited 171 Main Street Road Town Tortola VG1 110 British Virgin Islands Ladies and Gentlemen: Issuer Guarantor Registration Statement Act Debt Securities Indenture Trustee Guarantees We, as] [[LETTERHEAD OF DAVIS POLK & WARDWELL, HONG KONG SOLICITORS] May 1, 2013 CNOOC Limited 65th Floor, Bank of China Tower One Garden Road, Central Hong Kong Ladies and Gentlemen: Company Issuer Registration Statement Securities Act Debt Securities Indenture Trustee Guarantees CNOOC Limited, a limited liability company incorporated under the laws of Hong Kong (the “ We, as your counsel, have] [[LETTERHEAD OF WALKERS] 1 May 2013 Our Ref: AOD/ST/C4132-H08523 CNOOC Finance (2013) Limited c/o Intertrust Corporate Services (BVI) Limited 171 Main Street Road Town Tortola VG1 110 British Virgin Islands Dear Sirs CNOOC FINANCE (2013) LIMITED CNOOC Finance (2013) Limited Company Guarantor Registration Statement Commission Act Debt Securities Guarantees Indenture Trustee We have been asked to provide this legal opinion] [Computation of Ratio of Earnings to Fixed Charges (Unaudited) Earnings available for fixed charges are calculated first, by determining the sum of: (a) income (loss) from continuing operations before income taxes and equity income; (b) distributed equity income; (c) fixed charges, as defined below; and (d) amortization of capitalized interest, if any. From this total, we subtract capitalized interest and] [Consent of Independent Registered Public Accounting Firm Certified Public Accountants Hong Kong May 1, 2013 EX-23.1 8 d526339dex231.htm EX-23.1] [[LETTERHEAD OF RYDER SCOTT COMPANY, L.P.] Consent of Ryder Scott Company, L.P. Ryder Scott Company, L.P. Ryder Scott Company, L.P. Houston, Texas April 22, 2013 EX-23.2 9 d526339dex232.htm EX-23.2] [[LETTERHEAD OF GAFFNEY, CLINE & ASSOCIATES (CONSULTANTS)PTE LTD.] Consent of Gaffney, Cline & Associates (Consultants) Pte Ltd. Gaffney, Cline & Associates (Consultants) Pte Ltd. Stephen A. Sakowski Regional QA Director – Asia Pacific 80 Anson Road, #31-01C Fuji Xerox Towers, Singapore 079907 April 22, 2013 EX-23.3 10 d526339dex233.htm EX-23.3] [[LETTERHEAD OF LEE KEELING AND ASSOCIATES, INC.] Consent of Lee Keeling and Associates, Inc. Lee Keeling and Associates, Inc. Lee Keeling and Associates, Inc. 15 East Fifth Street, Suite 3500, Tulsa, Oklahoma 74103-4350 USA April 19, 2013 EX-23.4 11 d526339dex234.htm EX-23.4] [[LETTERHEAD OF MCDANIEL & ASSOCIATES CONSULTANTS LTD.] Consent of McDaniel & Associates Consultants Ltd. McDaniel & Associates Consultants Ltd. P.A. Welch, P. Eng. President & Managing Director 2200, Bow Valley Square 3, 255 - 5 Avenue SW Calgary, Alberta, T2P 3G6 April 19, 2013 EX-23.5 12 d526339dex235.htm EX-23.5] [[LETTERHEAD OF RPS] Consent of RPS RPS Debbie Perkins Vice President Houston, Texas April 19, 2013 EX-23.6 13 d526339dex236.htm EX-23.6] []

[FORM F-3 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 CNOOC Limited Issuer Hong Kong (State or Other Jurisdiction of Incorporation or Organization) Not Applicable (I.R.S. Employer Identification Number) 65th Floor, Bank of China Tower One Garden Road, Central Hong Kong Tel +852 2213 2500 National Corporate Research, Ltd. 10 East 40th Street, 10th Floor New York, NY 10016 (800)] [Dated as of July 30, 2009 NEXEN INC. and DEUTSCHE BANK TRUST COMPANY AMERICAS SECOND SUPPLEMENTAL INDENTURE to the TRUST INDENTURE Dated as of May 4, 2007 Second Supplemental Indenture NEXEN INC. Issuer DEUTSCHE BANK TRUST COMPANY AMERICAS Trustee THIS SECOND SUPPLEMENTAL INDENTURE (this “ RECITALS OF THE COMPANY WHEREAS Original Indenture WHEREAS WHEREAS WHEREAS WHEREAS 2019 Notes 2039 Notes] [NEXEN INC. and DEUTSCHE BANK TRUST COMPANY AMERICAS THIRD SUPPLEMENTAL INDENTURE to the TRUST INDENTURE Dated as of May 4, 2007 Third Supplemental Indenture CBCA Nexen AmalCo DEUTSCHE BANK TRUST COMPANY AMERICAS Trustee THIRD SUPPLEMENTAL INDENTURE (this “ RECITALS OF THE COMPANY WHEREAS Nexen NPII Amalgamation WHEREAS WHEREAS Original Indenture First Supplemental Indenture Second Supplemental Indenture Indenture Securities WHEREAS WHEREAS] [The proposed text of the Fourth Supplemental Indenture is set forth below. The text of the Fourth Supplemental Indenture as executed and delivered may include minor changes from the proposed text, as deemed appropriate by the parties thereto. Dated as of March [ ], 2013 NEXEN INC. and DEUTSCHE BANK TRUST COMPANY AMERICAS and CNOOC LIMITED FOURTH SUPPLEMENTAL INDENTURE to] [THIS SECOND SUPPLEMENTAL INDENTURE (the “Supplemental Indenture”) dated as of February 4, 1999. BETWEEN: CANADIAN OCCIDENTAL PETROLEUM LTD. OF THE FIRST PART OF and - CIBC MELLON TRUST COMPANY OF THE SECOND PART WITNESSETH THAT: WHEREAS AND WHEREAS AND WHEREAS AND WHEREAS NOW THEREFORE 1. INTERPRETATIONS AND AMENDMENTS 1.1 Supplemental Indenture This “Supplemental Indenture”, “hereto”, “herein”, “hereof’, “hereby”, “hereunder” and] [Dated as of February 24, 2013 . NEXEN INC -and- CIBC MELLON TRUST COMPANY SIXTH SUPPLEMENTAL INDENTURE to the TRUST INDENTURE Dated as of April 28, 1998 TABLE OF CONTENTS 1. INTERPRETATIONS AND AMENDEMENTS 2 1.1 Supplemental Indenture 2 1.2 Definitions in Indenture 3 1.3 Interpretation not Affected by Headings 3 1.4 Number; Persons 3] [Dated as of March ●, 2013 NEXEN INC. -and- CIBC MELLON TRUST COMPANY -and- THE BANK OF NEW YORK MELLON -and- CNOOC LIMITED SEVENTH SUPPLEMENTAL INDENTURE to the TRUST INDENTURE Dated as of April 28, 1998 TABLE OF CONTENTS 1. INTERPRETATIONS AND AMENDEMENTS 2 1.1 Supplemental Indenture 2 1.2 Definitions in Indenture 2 1.3 Interpretation not Affected by Headings 3] [OPINION OF DAVIS POLK & WARDWELL LLP March 7, 2013 CNOOC Limited 65th Floor, Bank of China Tower One Garden Road, Central Hong Kong Ladies and Gentlemen: We, as your counsel, have examined originals or copies of such documents, corporate records, certificates of public officials and other instruments as we have deemed necessary or advisable for the purpose of rendering] [March 5, 2013 The Directors CNOOC Limited 65th Floor, Bank of China Tower One Garden Road, Central Hong Kong Dear Sirs, We are aware of the incorporation by reference in this Registration Statement on Form F-3 of CNOOC Limited for the registration of debt securities and guarantees of CNOOC Limited of our report dated August 21, 2012 relating to the] [Consent of Independent Registered Public Accounting Firm Certified Public Accountants Hong Kong March 5, 2013 EX-23.1 18 dp36639_ex2301.htm EXHIBI 23.1] [] [1.]