EXHIBIT 99.1
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                              AMENDED FORM 51-101F2
                           REPORT ON RESERVES DATA BY
                      INTERNAL QUALIFIED RESERVES EVALUATOR



To the Board of Directors of Nexen Inc. (the "Company"):

1.     Company  staff and I have  evaluated  the  Company's  reserves data as at
       December 31, 2005. The reserves data consist of the following:

       (a)    proved oil and gas reserve quantities  estimated as at last day of
              the  Company's  most  recently  completed   financial  year  using
              constant prices and costs; and

       (b)    the related standardized measure.

       (both (a) and (b) form part of the "FAS 69 Disclosures  about Oil and Gas
       Producing Activities" contained in the Company's  Supplementary Financial
       Information in its Annual Report on Form 10-K).

2.     The reserves data have been prepared in accordance with:

       (a)    United   States'   Securities   and  Exchange   Commission   (SEC)
              requirements;

       (b)    generally  accepted  industry  practices  in the United  States as
              promulgated by the Society of Petroleum Engineers; and

       (c)    the  standards  of the Canadian  Oil and Gas  Evaluation  Handbook
              modified to the extent necessary to reflect SEC requirements.

       (collectively, the Nexen Reserves Standards).

3.     The reserves data are the responsibility of the Company's management.  My
       responsibility  is to express  an  opinion  whether  the  evaluation  was
       carried out in accordance with the Nexen Reserves Standards.

4.     I am not  independent  of the  Company,  within  the  meaning of the term
       "independent" under National Instrument 51-101.

5.     Among  other  things,  with  respect  to  matters  regarding   royalties,
       operating  costs,  development  plans and  costs,  abandonment  plans and
       costs,  and income taxes  (where  applicable),  I have placed  reasonable
       reliance on the  information  and  decisions  of others in their areas of
       authority, responsibility and expertise within the Company.


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6.     In my opinion,  the  reserves  data has, in all material  respects,  been
       prepared in accordance with the Nexen Reserves Standards.

7.     Reserves  are  estimates  only and not  exact  quantities.  Estimates  of
       economically recoverable oil and natural gas reserves and future net cash
       flows  are  based  on a  number  of  variable  factors,  assumptions  and
       judgements  regarding future events.  It is believed that the factors and
       assumptions   used  and  judgements  made  in  estimating   reserves  are
       reasonable  based on the information  available at the time the estimates
       were  prepared.  Actual  results  will vary and such  variances  could be
       material.

8.     I  have  no   responsibility  to  update  this  opinion  for  events  and
       circumstances occurring after the date of this opinion.

9.     I have  signed  this Form F2 in my  capacity as an employee of Nexen Inc.
       and not in my personal capacity.




/s/ Ian McDonald
-----------------------
IAN MCDONALD
NEXEN INC.
INTERNAL QUALIFIED RESERVES EVALUATOR
CALGARY, ALBERTA

FEBRUARY 16, 2006






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