EXHIBIT 31.1
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CERTIFICATIONS

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

1.       I have reviewed this quarterly report on Form 10-Q of Nexen Inc.

2.       Based on my knowledge, this quarterly 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 quarterly report;

3.       Based on my knowledge, the financial statements, and other financial
         information included in this quarterly 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 quarterly 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-1(e)) 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 quarterly report is being prepared;

         (b)   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

         (c)   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:    October 18, 2004                  /s/ Charles W. Fischer
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                                           Charles W. Fischer
                                           President and Chief Executive Officer