Nexen Shareholders Approve Plan of Arrangement with CNOOC Limited and CNOOC Canada Holding Ltd.

 Nexen Shareholders Approve Plan of Arrangement with CNOOC Limited and CNOOC
                             Canada Holding Ltd.

  PR Newswire

  CALGARY, Alberta, September 20, 2012

CALGARY, Alberta, September 20, 2012 /PRNewswire/ --

Nexen Inc. (TSX, NYSE: NXY) announced today that the holders of its common
shares and the holders of the cumulative redeemable class A rate reset
preferred shares, series 2 (the "preferred shareholders") have approved the
Plan of Arrangement, pursuant to the Arrangement Agreement entered into on
July 23, 2012 (the "arrangement"), in connection with the proposed acquisition
of Nexen Inc. by CNOOC Limited through CNOOC Canada Holding Ltd.

The arrangement was approved by approximately 99% of the votes cast by Nexen
common shareholders and approximately 87% of the votes cast by Nexen preferred
shareholders at the special meeting held on September 20, 2012.

The closing of the arrangement remains subject to the granting of the final
order by the Court of Queen's Bench of Alberta, the receipt of required
regulatory approvals and the satisfaction or waiver of the other customary
closing conditions.

Nexen Inc. is an upstream oil and gas company listed on the Toronto and New
York stock exchanges under the symbol NXY. Nexen operates oil sands and shale
gas in Western Canada and conventional exploration and development primarily
in the UK North Sea, offshore West Africa and Gulf of Mexico.

Forward-looking statements & Information

This press release contains forward-looking statements and forward-looking
information within the meaning of applicable securities laws and which are
based on the expectations, estimates and projections of management of the
parties as of the date of this news release unless otherwise stated. The use
of any of the words "expect", "anticipate", "continue", "estimate",
"objective", "ongoing", "may", "will", "project", "should", "believe",
"plans", "intends" and similar expressions are intended to identify
forward-looking statements or information. More particularly and without
limitation, this press release contains forward-looking statements and
information concerning: the anticipated benefits of the transaction to the
parties, their respective securityholders and certain of the countries in
which Nexen operates; the timing and anticipated receipt of required
regulatory and court approvals for the transaction; the ability of the parties
to satisfy the other conditions to, and to complete, the transaction; and the
anticipated timing of the closing of the transaction.

In respect of the forward-looking statements and information concerning the
anticipated benefits and completion of the proposed transaction and the
anticipated timing for completion of the transaction, Nexen and CNOOC Limited
have provided such in reliance on certain assumptions that they believe are
reasonable at this time, including assumptions as to the ability of the
parties to receive, in a timely manner and on satisfactory terms, the
necessary regulatory, court, stock exchange and other third party approvals,
including but not limited to the receipt of applicable foreign investment
approval required in Canada, the United States and elsewhere and the required
approvals from the Government of the People's Republic of China and in other
foreign jurisdictions; the ability of the parties to satisfy, in a timely
manner, the other conditions to the closing of the transaction; and other
expectations and assumptions concerning the transaction and the operations and
capital expenditure plans of Nexen following completion of the transaction.
The anticipated dates provided may change for a number of reasons, including
the inability to secure necessary regulatory, court or other third party
approvals in the time assumed or the need for additional time to satisfy the
other conditions to the completion of the transaction. Accordingly, readers
should not place undue reliance on the forward-looking statements and
information contained in this press release.

Since forward-looking statements and information address future events and
conditions, by their very nature they involve inherent risks and
uncertainties. Actual results could differ materially from those currently
anticipated due to a number of factors and risks. Risks and uncertainties
inherent in the nature of the transaction include the failure of Nexen and
CNOOC Limited to obtain necessary regulatory, court and other third party
approvals, including those noted above, or to otherwise satisfy the conditions
to the completion of the transaction, in a timely manner, or at all. Failure
to so obtain such approvals, or the failure of the parties to otherwise
satisfy the conditions to or complete the transaction, may result in the
transaction not being completed on the proposed terms, or at all. In addition,
if the transaction is not completed, and Nexen continues as an independent
entity, there are risks that the announcement of the transaction and the
dedication of substantial resources of Nexen to the completion of transaction
could have an impact on Nexen's current business relationships (including with
future and prospective employees, customers, distributors, suppliers and
partners) and could have a material adverse effect on the current and future
operations, financial condition and prospects of Nexen.Furthermore, the
failure of Nexen to comply with the terms of the definitive agreement may
result in Nexen being required to pay a fee to CNOOC Limited, the result of
which could have a material adverse effect on Nexen's financial position and
results of operations and its ability to fund growth prospects and current
operations.

Readers are cautioned that the foregoing list of factors is not exhaustive.
Additional information on other factors that could affect the operations or
financial results of the parties are included in reports on file with
applicable securities regulatory authorities.

The forward-looking statements and information contained in this press release
are made as of the date hereof and the parties undertake no obligation to
update publicly or revise any forward-looking statements or information,
whether as a result of new information, future events or otherwise, unless so
required by applicable securities laws.

For further information:

For investor relations inquiries, please contact:Janet Craig Vice President,
Investor Relations +1(403)699-4230

For media and general inquiries, please contact: Pierre Alvarez Vice
President, Corporate Relations +1(403)699-5202