ATP Announces Management's Estimate of 585 Bcfe of New Recoverable Hydrocarbons.

HOUSTON -- ATP Oil & Gas Corporation (NASDAQ:ATPG) today announced management's estimate of 585 Bcfe of recoverable hydrocarbons from reservoirs not included in ATP's year-end 2005 reserve reports. As of December 31, 2005, ATP reported 1.1 Tcfe of proved, probable and possible reserves, 758 Bcfe of proved and probable reserves, and 527 Bcfe of proved reserves, all prepared by third party independent reservoir engineers. Management's estimate of recoverable hydrocarbons of 585 Bcfe is not included in these amounts.

Oil and gas reservoirs with logged hydrocarbons, including those recently acquired by ATP, have not yet been evaluated by third party independent reservoir engineers. In addition, ATP has acquired several properties without logged hydrocarbons which have demonstrated exploration opportunities that management believes are relatively low-risk and most are step-out locations to existing reserves.

Twelve ATP properties with logged hydrocarbons have been evaluated by management and it is management's estimate that they contain recoverable hydrocarbons of 360 Bcfe. Five of those properties with logged hydrocarbons plus three additional properties have identified exploration targets. It is management's estimate that these exploration opportunities contain 225 Bcfe of recoverable hydrocarbons. The following table sets forth management's estimates of the recoverable hydrocarbons for those properties acquired during 2006 and those properties owned as of December 31, 2005:

Management's Estimates
----------------------------------------------------------------------
                             Logged       Exploration       Total
                           Hydrocarbons   Opportunities    Estimated
                                                          Hydrocarbons
------------------------  -------------  --------------  -------------
2006 Acquisitions
------------------------  -------------  --------------  -------------
  Telemark, Mirage,         190 Bcfe        60 Bcfe        250 Bcfe
   Oasis and Morgus
  Green Canyon 37            45 Bcfe        50 Bcfe         95 Bcfe
------------------------  -------------  --------------  -------------

Properties owned at
 12/31/2005
------------------------  -------------  --------------  -------------
  Gomez                      30 Bcfe        70 Bcfe        100 Bcfe
  Other Properties           95 Bcfe        45 Bcfe        140 Bcfe
------------------------  -------------  --------------  -------------
Total                       360 Bcfe        225 Bcfe       585 Bcfe
------------------------  -------------  --------------  -------------

The largest accumulation of unrecorded recoverable hydrocarbons is 250 Bcfe at the four-property group comprising Telemark (Atwater Valley 63), Mirage (Mississippi Canyon 941), Oasis (Mississippi Canyon 943) and Morgus (Mississippi Canyon 942). Previous drilling with logged hydrocarbons at Telemark, Mirage and Morgus has identified approximately 190 Bcfe of recoverable hydrocarbons at those locations. Management believes an additional 60 Bcfe may be recoverable through exploration. ATP has begun building a spar that is scheduled to be installed at the complex in early 2008. While final design parameters may change, initial design is for at least two risers, a 2,000 horsepower platform drilling rig, 20,000 to 30,000 Bbls of daily oil throughput and 60 to 100 MMcfe of daily natural gas throughput. ATP has a 100% working interest in and is operator of all four blocks at Telemark, Mirage, Oasis and Morgus.

The next largest area of unrecorded hydrocarbons in management's opinion is 100 Bcfe at ATP's Gomez (Mississippi Canyon 711) property. Recent drilling at the #5 well and additional identified sands in the existing wells provide an estimated 30 Bcfe of logged hydrocarbons in zones that were not previously recorded in ATP's reserve reports. A location in the southern portion of the block and targets at Mississippi Canyon 667/668, immediately north of Gomez, account for an estimated 70 Bcfe of recoverable hydrocarbons from exploratory targets. Production at those locations will flow through the facility at Gomez. Current capacity of the Gomez production facility is 20,000 Bbls of oil per day and 60 MMcfe per day of natural gas. ATP has a 100% working interest in and is operator of the blocks at Gomez.

Green Canyon 37, a 2006 acquisition, accounts for the third largest area of unbooked hydrocarbons. Management's estimate of recoverable hydrocarbons is approximately 95 Bcfe and is essentially split between an exploration target and zones identified by logged hydrocarbons. Current plans are for work to begin at this location in 2007 or 2008, with first production approximately 18 months later. ATP has a 100% working interest in and is operator of Green Canyon 37.

Other operations in the Gulf of Mexico include Ladybug (Garden Banks 409), West Cameron 663, High Island A-589, Ship Shoal 351 and South Marsh Island 189/190. At Cheviot in the North Sea, ATP has identified recoverable hydrocarbons, all from logged hydrocarbons, which have not been booked. There are also exploratory targets at Cheviot and Wenlock that are still being evaluated that are not included in these estimates. Collectively, these properties account for another 140 Bcfe net to ATP (95 Bcfe from logged hydrocarbons and 45 Bcfe from exploratory targets) of recoverable hydrocarbons based on management's estimates. ATP has a 50% to 100% working interest in these blocks and is operator of all of these blocks.

ATP is currently working with its independent reservoir engineers to determine their estimates of the amount and SEC classification of these recoverable hydrocarbons. In addition, ATP will continue to evaluate these and other properties for unrecorded recoverable hydrocarbons as well as adjustments to those reserves that have been recorded.

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 Global Select 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" and "possible" and we use the term "recoverable hydrocarbons" 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 and possible reserves in this news release have been prepared by our independent third party engineers and all estimates of recoverable hydrocarbons have been prepared by management. More information about the risks and uncertainties relating to ATP's forward-looking statements are found in our SEC filings.