EXHIBIT 31.2

CERTIFICATIONS

I, Marvin F. Romanow, certify that:

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

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  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  Rule
     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  reasonably  likely  to  materially  affect,  the
           registrant's internal control over financial reporting; and;

5.   The registrant's other certifying  officer 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 the 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 26, 2007                            /s/ Marvin F. Romanow
                                                     ---------------------------
                                                     Marvin F. Romanow
                                                     Executive Vice President
                                                     and Chief Financial Officer