Nexen Announces Completion of Acquisition by CNOOC Limited

          Nexen Announces Completion of Acquisition by CNOOC Limited

PR Newswire

CALGARY, Feb. 25, 2013

CALGARY, Feb. 25, 2013 /PRNewswire/ - Nexen Inc. ("Nexen" or the "Company",
TSX, NYSE: NXY) announced today that CNOOC Limited has completed its
acquisition of the Company. Pursuant to the plan of arrangement (the
"Arrangement") holders of Nexen common shares will receive cash proceeds of US
$27.50, without interest, and holders of Nexen preferred shares will receive
cash proceeds of CAD $26.00, plus accrued and unpaid dividends up to, but
excluding, the closing date of the Arrangement, without interest.

Kevin Reinhart will continue as CEO of Nexen and will maintain responsibility
for all of Nexen's operations. The Company's Calgary headquarters will
continue to be responsible for managing all of Nexen's existing assets as well
as CNOOC Limited's North and Central American assets.

Nexen's common and preferred shares are expected to be delisted from the
Toronto Stock Exchange (the "TSX") in a few trading days. Nexen's common
shares are expected to cease being traded on the NYSE prior to the market
opening on February 26, 2013, and will subsequently be delisted.

Nexen Establishes New Board of Directors

Following the completion of the transaction, Nexen established a new Board of
Directors comprised of representatives of CNOOC Limited and Nexen, as well as
independent directors. Mr. Li Fanrong has been appointed Chair of the Board of
Nexen. Mr. Li Fanrong is the CEO of CNOOC Limited, and has more than 28 years
of experience in the oil and gas industry including in the North Sea. The
other directors serving on the Nexen Board are Mr. Fang Zhi, Vice President
CNOOC Limited, Mr. Kevin Reinhart, Mr. Barry Jackson, Mr. Thomas O'Neill and
Mr. William Berry.

About Nexen

Nexen Inc. is a wholly-owned subsidiary of CNOOC Limited. Nexen is focused on
three growth strategies: oil sands and shale gas in western Canada and
conventional exploration and development primarily in the North Sea, offshore
West Africa and deepwater Gulf of Mexico.

Forward-Looking Statements

Certain statements in this Release constitute "forward-looking statements"
(within the meaning of the United States Private Securities Litigation Reform
Act of 1995, as amended) or "forward-looking information" (within the meaning
of applicable Canadian securities legislation). Such statements or information
(together "forward-looking statements") are generally identifiable by the
forward-looking terminology used such as "will", "intends", "expect", "should"
or other similar words. More particularly and without limitation, this Release
contains forward-looking statements and information concerning the delisting
of the common shares and the preferred shares from the TSX and the NYSE, as
applicable.

In respect of the forward-looking statements and information concerning the
delisting of the common shares and the preferred shares from the TSX and NYSE,
as applicable, Nexen has provided such in reliance on certain assumptions that
it believes are reasonable at this time, including assumptions as to the time
necessary, and the ability of Nexen to complete the delisting of the common
shares and the preferred shares from the TSX and the NYSE, as applicable. The
date of delisting may be delayed or changed for a number of reasons.
Accordingly, readers should not place undue reliance on the forward-looking
statements and information contained in this Release concerning these times.

Nexen undertakes 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.

SOURCE Nexen Inc.

Contact:

For investor relations inquiries, please contact:

Janet Craig
Vice President, Investor Relations
(403) 699-4230

For media and general inquiries, please contact:

Pierre Alvarez
Vice President, Corporate Relations
(403) 699-5202

801 - 7^th Ave SW
Calgary, Alberta, Canada T2P 3P7
www.nexeninc.com