[Registration No. 333-188261 Registration No. 333-188261-03 Registration No. 333-188261-04 Issuer Free Writing Prospectus dated April 28, 2015 Relating to Preliminary Prospectus Supplement dated April 27, 2015 CNOOC LIMITED Pricing Term Sheet 2.625% Notes due 2020 (the “2020 Notes”) Issuer: CNOOC Finance (2015) Australia Pty Ltd Guarantor: CNOOC Limited Principal Amount: US$1,500,000,000 May 5, 2020 Coupon: 2.625% Public Offering Price: 99.716%]