UNITED STATES


SECURITIES AND EXCHANGE COMMISSION


Washington, D.C. 20549




FORM 10-K/A




AMENDMENT NO. 1




ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(D) OF


THE SECURITIES EXCHANGE ACT OF 1934




For the year ended December 31, 2009


Commission File Number 1-6702




NEXEN INC.


Incorporated under the Laws of Canada









98-6000202


(I.R.S. Employer Identification No.)




801 – 7th Avenue S.W.


Calgary, Alberta, Canada T2P 3P7


Telephone: (403) 699-4000


Website: www.nexeninc.com




SECURITIES REGISTERED PURSUANT TO SECTION 12(B) OF THE ACT:




TITLE

EXCHANGE REGISTERED ONCommon shares, no par value

The New York Stock Exchange

The Toronto Stock ExchangeSubordinated Securities, due 2043

The New York Stock Exchange

The Toronto Stock Exchange







SECURITIES REGISTERED PURSUANT TO SECTION 12(G) OF THE ACT: NONE.




Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.




Yes x  No o





Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Exchange Act.




Yes o  No x





Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.




Yes x  No o




Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. x




Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer”, “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.




Large accelerated filer x  Accelerated filer o  Non-accelerated filer o  Smaller reporting company o




Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).




Yes o  No x




On June 30, 2009, the aggregate market value of the voting shares held by non-affiliates of the registrant was approximately Cdn$13 billion based on the Toronto Stock Exchange closing price on that date. On January 31, 2010, there were 523,285,022 common shares issued and outstanding.
















EXPLANATORY NOTE





This Amendment No. 1 on Form 10-K/A (this "Amendment") amends the Annual Report on Form 10-K for the year ended December 31, 2009 filed on February 25, 2010 (the "Original Filing").  Nexen Inc. (the "Company") has filed this Amendment to file the following exhibits (which will replace those filed with the Original Filing):





23.2
Report of Third Party, DeGolyer and MacNaughton (selected United Kingdom properties).23.3
Report of Third Party, DeGolyer and MacNaughton (selected Yemen properties).23.4
Report of Third Party, DeGolyer and MacNaughton (selected Nigeria properties).23.5
Consent of DeGolyer and MacNaughton.23.6
Report of Third Party, McDaniel & Associates Consultants Ltd. (selected Canadian properties).23.7
Report of Third Party, McDaniel & Associates Consultants Ltd. (Syncrude).23.8
Consent of McDaniel & Associates Consultants Ltd.23.9
Report of Third Party, Ryder Scott Company L.P. (selected Gulf of Mexico properties).23.10
Consent of Ryder Scott Company L.P.





Other information contained in the Original Filing has not been updated.  Therefore, this Amendment should be read together with other documents that the Company has filed with the Securities and Exchange Commission subsequent to the filing of the Original Filing.  Information in such reports and documents updates and supersedes certain information contained in this Amendment.  The filing of this Amendment shall not be deemed an admission that the Original Filing, when made, included any known, untrue statement of material fact or knowingly omitted to state a material fact necessary to make a statement not misleading.








TABLE OF CONTENTSPAGEPart II. – OTHER INFORMATIONITEM 15.  EXHIBITS, FINANCIAL STATEMENT SCHEDULES
1Signatures
2










PART II. — OTHER INFORMATION






ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES






EXHIBITS




The following exhibits are being filed as part of this Annual Report on Form 10-K/A:




23.2
Report of Third Party, DeGolyer and MacNaughton

(selected United Kingdom properties).23.3
Report of Third Party, DeGolyer and MacNaughton

(selected Yemen properties).23.4
Report of Third Party, DeGolyer and MacNaughton

(selected Nigeria properties).23.5
Consent of DeGolyer and MacNaughton.23.6
Report of Third Party, McDaniel & Associates Consultants Ltd.

(selected Canadian properties).23.7
Report of Third Party, McDaniel & Associates Consultants Ltd.

(Syncrude).23.8
Consent of McDaniel & Associates Consultants Ltd.23.9
Report of Third Party, Ryder Scott Company L.P.

(selected Gulf of Mexico properties).23.10
Consent of Ryder Scott Company L.P.31.1
Certification of Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.31.2
Certification of Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.




























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SIGNATURES





Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the Company has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized, on December 15, 2010.






NEXEN INC.By:
/s/  Marvin F. RomanowMarvin F. RomanowPresident, Chief Executive Officer and Director


















2