EXHIBIT 31.1
                                                                   ------------


CERTIFICATIONS

I, Charles W. Fischer, President and Chief Executive Officer, certify that:

1.    I have reviewed the Annual  Report on Form 10-K/A of Nexen,  Inc. for the
      year ended  December 31, 2005 as filed with the  Securities  and Exchange
      Commission on February 23, 2006, as amended by Amendment No.1 (as amended
      to date, the "Report");

2.    Based on my knowledge,  this Report does not contain any untrue statement
      of a material fact or omit to state a material fact necessary to make the
      statements  made,  in  light  of  the  circumstances   under  which  such
      statements  were made, not misleading  with respect to the period covered
      by this Report;

3.    Based on my knowledge,  the  financial  statements,  and other  financial
      information  included  in this  Report,  fairly  present in all  material
      respects the financial condition, results of operations and cash flows of
      the registrant as of, and for, the periods presented in this Report;

4.    The registrant's  other  certifying  officer(s) and I are responsible for
      establishing  and  maintaining  disclosure  controls and  procedures  (as
      defined in  Exchange  Act Rules  13a-15(e)  and  15d-15(e)  and  internal
      control  over  financial  reporting  (as  defined in  Exchange  Act Rules
      13a-15(f) and 15d-15(f)) for the registrant and we have:

      (a)   designed such disclosure  controls and  procedures,  or caused such
            disclosure  controls  and  procedures  to  be  designed  under  our
            supervision,  to ensure that material  information  relating to the
            registrant,  including its consolidated subsidiaries, is made known
            to us by others  within  those  entities,  particularly  during the
            period in which this Report is being prepared;

      (b)   designed such internal control over financial reporting,  or caused
            such internal control over financial reporting to be designed under
            our  supervision,  to provide  reasonable  assurance  regarding the
            reliability of financial reporting and the preparation of financial
            statements  for  external  purposes in  accordance  with  generally
            accepted accounting principles;

      (c)   evaluated the effectiveness of the registrant's disclosure controls
            and procedures and presented in this Report our  conclusions  about
            the effectiveness of the disclosure controls and procedures,  as of
            the  end of the  period  covered  by  this  Report  based  on  such
            evaluation; and

      (d)   disclosed  in this Report any change in the  registrant's  internal
            control  over  financial   reporting   that  occurred   during  the
            registrant's  most recent fiscal quarter (the  registrant's  fourth
            fiscal quarter in the case of an annual report) that has materially
            affected,  or is  likely to  materially  affect,  the  registrant's
            internal control over financial reporting; and

5.    The registrant's other certifying officer(s) and I have disclosed,  based
      on  our  most  recent  evaluation  of  internal  control  over  financial
      reporting,  to the  registrant's  auditors  and the  audit  committee  of
      registrant's  board of directors (or persons  performing  the  equivalent
      function):

      (a)   all significant  deficiencies and material weaknesses in the design
            or operation of internal control over financial reporting which are
            reasonably  likely to adversely affect the registrant's  ability to
            record, process, summarize and report financial information; and

      (b)   any fraud,  whether or not material,  that  involves  management or
            other  employees  who have a significant  role in the  registrant's
            internal control over financial reporting.


Date:  April 2, 2007                             /s/ Charles W. Fischer
                                                 -----------------------------
                                                 Charles W. Fischer
                                                 President and Chief Executive
                                                 Officer