ATP Oil & Gas Corporation Announces Record Proved Reserves

Business Wire, March 9, 2006

HOUSTON -- ATP Oil & Gas Corporation (Nasdaq:ATPG) today announced that at December 31, 2005, ATP achieved a record reserve replacement ratio of 1,367% for 2005. The Company's year-end natural gas and oil proved reserves were 527.5 Bcfe (67% natural gas) with a pre-tax PV-10 of $2.7 billion, compared to 275.2 Bcfe and a $733 million pre-tax PV-10 at year-end 2004. Proved developed reserves more than doubled (up 112%) to a record 128.4 Bcfe during 2005. At December 31, 2005, proved and probable reserves were 758.3 Bcfe (68% natural gas) with a pre-tax PV-10 of $4.2 billion.

ATP's 2005 proved and probable reserve reports were prepared by independent third-party reservoir engineers. The proved reserve quantities and classifications contained in the reports prepared by the independent reservoir engineers conform to the definition as set forth in the in accordance with parameters established by the Securities and Exchange Commission ("SEC") Regulation S-X Part 210.4-10 (a) as clarified by subsequent Commission Staff Accounting Bulletins. ATP will make accessible copies of the certification letters from the independent third-party reservoir engineers on the Company's web site www.atpog.com. The reports will be posted under Investor Info-Annual/Quarterly Reports and will be made available on March 9, 2006.

Proved Reserves
Prepared by independent reservoir engineers
December 31, 2005
                         Gulf of Mexico     North Sea    Consolidated
                        ----------------- -------------- -------------
Proved
(MMcfe)
 Developed                     114,379.5       13,989.2     128,368.8

 Undeveloped                   117,650.3      281,476.0     399,126.3
                        ----------------- -------------- -------------
 Total                         232,029.8      295,465.2     527,495.1
                        ================= ============== =============

Pre-tax PV-10
($'s in millions)
 Developed                        $784.8          $82.6        $867.4
 Undeveloped                      $607.7       $1,209.2      $1,817.0
                        ----------------- -------------- -------------
 Total                          $1,392.5       $1,291.8      $2,684.3
                        ================= ============== =============



Proved & Probable Reserves
Prepared by independent reservoir engineers
December 31, 2005
                         Gulf of Mexico     North Sea    Consolidated
                        ----------------- -------------- -------------
Proved & Probable
(MMcfe)
 Developed                     155,532.6       22,298.5     177,831.1
 Undeveloped                   178,728.8      401,693.0     580,421.8
                        ----------------- -------------- -------------
 Total                         334,261.5      423,991.5     758,252.9
                        ================= ============== =============

Pre-tax PV-10
($'s in millions)
 Developed                      $1,039.8         $116.9      $1,156.7
 Undeveloped                      $956.9       $1,989.0      $2,945.9
                        ----------------- -------------- -------------
 Total                          $1,996.7       $2,105.9      $4,102.6
                        ================= ============== =============


Top 5 Properties
(Based on Proved & Probable Reserves)
Prepared by independent reservoir engineers
December 31, 2005
                     Cheviot     MC 711     Tors     King's    Venture
                                                       Peak
                   ---------- ---------- ---------- --------- --------
Reserves           North Sea   Gulf of   North Sea  Gulf of    North
                                Mexico                Mexico     Sea
                   ---------- ---------- ---------- --------- --------
(Bcfe)
 Proved                182.3       93.1       72.9      55.7     26.3
 Probable               47.2       47.2       42.2      26.4     30.8
                   ---------- ---------- ---------- --------- --------
 Total                 229.5      140.3      115.1      82.1     57.2
                   ========== ========== ========== ========= ========

About ATP Oil & Gas

ATP Oil & Gas is focused on development and production of natural gas and oil in the Gulf of Mexico and the North Sea. The Company trades publicly as ATPG on the NASDAQ National Market.

Forward-looking Statements

Certain statements included in this news release are "forward-looking statements" under the Private Securities Litigation Reform Act of 1995. ATP cautions that assumptions, expectations, projections, intentions, or beliefs about future events may, and often do, vary from actual results and the differences can be material. Some of the key factors which could cause actual results to vary from those ATP expects include changes in natural gas and oil prices, the timing of planned capital expenditures, availability of acquisitions, uncertainties in estimating proved reserves and forecasting production results, operational factors affecting the commencement or maintenance of producing wells, the condition of the capital markets generally, as well as our ability to access them, and uncertainties regarding environmental regulations or litigation and other legal or regulatory developments affecting our business. The SEC has generally permitted oil and gas companies, in filings made with the SEC, to disclose only proved reserves that a company has demonstrated by actual production or conclusive formation tests to be economically and legally producible under existing economic and operating conditions. We and our independent third party reservoir engineers use the terms "probable" to describe volumes of reserves potentially recoverable through additional drilling or recovery techniques that the SEC's guidelines may prohibit us from including in filings with the SEC. These estimates are by their nature more speculative than estimates of proved reserves. All estimates of probable reserves in this release have been prepared by our independent third party engineers. More information about the risks and uncertainties relating to ATP's forward-looking statements are found in our SEC filings.