Exhibit 23.3
4 April 2018
China National Offshore Oil Corporation Limited
No. 25, Chaoyangmenbei Daijie
Dongcheng District
Beijing 100010,
P.R. China
Dear Sir,
Consent of Gaffney, Cline & Associates
As independent reserves advisors of CNOOC Limited (CNOOC), Gaffney, Cline & Associates (GCA) hereby confirms that it has granted and not withdrawn its consent to the references to GCA under the caption “Experts” in the Registration Statement on FormF-3 and related Prospectus Supplement of CNOOC Limited for the registration of debt securities and guarantees and to the incorporation by reference therein of our reports entitled“Independent Letter – The Missan Oil Fields In Eastern Iraq Estimated Proved Reserves and Financial Data, Based on SEC Rules as of 31 December 2017”and“Independent Letter – The Greater Angostura Fields Block 2C, Trinidad& Tobago Estimated Proved Reserves and Financial Data, Based on SEC Rules as of 31 December 2017”as of March 2018 included on Form20-F of CNOOC’s Annual Report for the year ended December 31, 2017, filed with the Securities and Exchange Commission.
| Yours faithfully, | ||||
| Gaffney, Cline & Associates (Consultants) Pte Ltd | ||||
/s/ Stephen M. Lane | ||||
| Stephen M. Lane, | ||||
| Technical Director | ||||
