Endeavour Announces Increase in Proved and Probable Reserves in 2010

HOUSTON, February 24, 2011 /PRNewswire/ --

Endeavour International Corporation (NYSE Amex: END) (LSE: ENDV) today announces an increase in proved and probable reserves as of December 31, 2010 resulting in a 419 percent reserve replacement rate of 2010 production, based on 2P reserves.

"Even with the sale of our Cygnus North Sea asset, we continue to grow the company's reserves strongly through the drill bit," said William L. Transier, chairman, chief executive officer and president. "Our 2010 successes are directly attributable to the efforts of our North Sea drilling and the development of our onshore US program, including a substantial enhancement to the value of Cygnus through appraisal drilling."

Proved and probable reserves at year-end 2010 increased to 43.7 million barrels of oil equivalent (mmboe) compared to 38.9 mmboe a year ago. Extensions, discoveries, sales and purchases added 6.3 mmboe during 2010. Production for the year was 1.5 mmboe.

The upward revisions in 2P reserves were the result of the appraisal well drilled in West Rochelle Block 15/26b, the addition of reserves from the Bacchus development and strong results from the Louisiana/Texas Haynesville program.

    
                          Net Reserves at December 31,

                                                     2010*

    Audited by: Netherland, Sewell  Oil       NGL        Gas      Equivalents
    and Associates, Inc.           (mbbl)    (mbbl)    (mmcf)         (mboe)

    Proved Developed
      Producing                     1,069        26     13,644          3,370
      Non-Producing                   153         6        192            191
    Proved Undeveloped              2,772         -     74,208         15,139
      Proved (1P)                   3,994        32     88,044         18,700
    Probable                       10,855        16     84,776         25,000
      Proved + Probable (2P)       14,849        48    172,820         43,700
    Possible                       10,874        19     77,128         23,747
      Proved + Probable + Possible
      (3P)                         25,723        67    249,948         67,447
 
    *Reserve information includes the purchase of the additional 20%
    (approximately 3.4mmboe of 2P reserves) of the Bacchus field in
    the North Sea.


 
                                                      2009

    Prepared by: Netherland,        Oil       NGL        Gas      Equivalents
    Sewell and Associates, Inc.    (mbbl)    (mbbl)    (mmcf)       (mboe)

    Proved Developed
      Producing                     1,212        26      4,458          1,981
      Non-Producing                   150         -      4,578            913
    Proved Undeveloped              1,973         5     80,064         15,322
      Proved (1P)                   3,335        31     89,100         18,216
    Probable                        7,352        20     79,919         20,692
      Proved + Probable (2P)       10,687        51    169,019         38,908
    Possible                        7,859        34     89,478         22,806
      Proved + Probable + Possible
      (3P)                         18,546        85    258,497         61,714

Endeavour International Corporation is an international oil and gas exploration and production company focused on the acquisition, exploration and development of energy reserves in the North Sea and United States. For more information, visit http://www.endeavourcorp.com.

Certain statements in this news release should be regarded as "forward-looking" statements within the meaning of the securities laws. These statements speak only of as of the date made. Such statements are subject to assumptions, risk and uncertainty. Actual results or events may vary materially.

As of January 1, 2010, the Securities and Exchange Commission (SEC) changed its rules to permit oil and gas companies, in their filings with the SEC, to disclose not only proved reserves, but also probable reserves and possible reserves. Proved oil and gas reserves are those quantities of oil and gas, which, by analysis of geoscience and engineering data, can be estimated with reasonable certainty to be economically producible - from a given date forward, from known reservoirs, and under existing economic conditions, operating methods, and government regulations - prior to the time at which contracts providing the right to operate expire. Probable reserves include those additional reserves that a company believes are as likely as not to be recovered and possible reserves include those additional reserves that are less certain to be recovered than probable reserves. We use may use certain terms in our news releases, such as "reserve potential," that the SEC's guidelines strictly prohibit us from including in filings with the SEC. In addition, we do not represent that the probable or possible reserves described herein meet the recoverability thresholds established by the SEC in its new definitions. Investors are urged to also consider closely the disclosure in our filings with the SEC, available from our website at http://www.endeavourcorp.com. Endeavour is also subject to the requirements of the London Stock Exchange and considers the disclosures in this release to be appropriate and/or required under the guidelines of that exchange.