ATP Provides Update on Gulf of Mexico Activities

ATP Oil & Gas Corporation (NASDAQ:ATPG) today announced that the Mississippi Canyon (MC) 941 #3 well at its Telemark location can be completed and the current drilling operation at MC 305 #2 in the Canyon Express area will need to be temporarily suspended. Both announcements are in compliance with the May 30, 2010 6:52 pm CDT Notice to Lessees (NTL) from the Minerals Management Service (MMS) which imposed a six month moratorium on drilling operations in the deepwater Gulf of Mexico as a result of the BP oil spill. Additional clarity regarding the application of the NTL was gained from other pronouncements and releases during ensuing days.

Addressing this update, T. Paul Bulmahn, Founder, Chairman and CEO of ATP expressed, "The tragedy of loss of human life and damage to the environment when discussing the BP oil spill cannot be overstated. Everyone at ATP Oil & Gas Corporation would like to extend our deepest sympathy and continued prayers and support to both individuals and families who have been impacted by these events. As nothing compares to the tragedy of loss of life, we also ask that no one forget the estimated forty-five thousand workers and the families of those workers that will find themselves unemployed as a result of the imposed deepwater work stoppage.”

Telemark Hub Update

ATP has begun the completion operations of the MC 941 #3 well which encountered 266’ of net pay, triple the amount of net pay found in the original discovery well. The NTL provides for completion operations which will allow this well to be placed on production. Access to vendor equipment and services which are necessary for the completion of this well have been limited due to preferential utilization in the BP oil spill. ATP now expects to commence production at the MC 941 #3 during the third quarter 2010. The next two wells at the Telemark Hub, the MC 941 #4 and MC 942 #2, originally scheduled for the third quarter and fourth quarter of 2010, now need to be rescheduled to early 2011 according to the NTL. There is currently one well producing at the Telemark Hub.

ATP operates the deepwater Telemark Hub with a 100% working interest and owns 100% of the ATP Titan and associated pipelines and infrastructure.

Gomez Hub Update

Existing production at the Gomez Hub (MC 711/754/755), ATP’s single largest producing property in the Gulf of Mexico, is unaffected by the NTL. ATP continues to produce the Gomez Hub. The MC 754 #1 well which has been completed is not impacted by the NTL and will be brought on production late 2010 following a pipeline lay and connection. Later in 2010 and early 2011, two wells, the MC 711 #9 and MC 711 #10, were scheduled to be drilled. These development wells would be the ninth and tenth wells drilled into the development reservoirs at Gomez. These wells will now be rescheduled to coincide with the end of the six month moratorium. There are currently five wells producing at the Gomez Hub.

ATP operates the Gomez Hub with a 100% working interest at MC 711 and 755 and a 75% working interest at MC 754.

Canyon Express Hub Update

At the MC 305 #2 natural gas well, ATP began an abandonment operation of one reservoir and a sidetrack into the same reservoir at an updip location. These operations were conducted in accordance with the abandonment permit issued on November 11, 2009 and the sidetrack permit issued May 12, 2010. As a result of the May 30, 2010 NTL, ATP will complete the abandonment operation but will temporarily suspend the sidetrack of the natural gas well. There are currently three wells producing at the Canyon Express Hub.

ATP operates the Canyon Express Hub with an approximate 50% working interest in the wells and associated pipelines.

Liquidity, Production and CAPEX

On April 23^rd, 2010 ATP issued $1.5 billion in Senior Secured Second Lien Notes. Net proceeds from the transaction were used to repay outstanding loans under ATP’s prior credit facility and provide $131.4 million in additional liquidity to the company’s balance sheet. In conjunction with the notes offering, ATP also closed a $100 million Senior Secured First Lien revolving credit facility. This facility remains undrawn and available to ATP.

ATP reaffirms its previously announced production guidance for the second quarter of 2.0 MMBoe to 2.5 MMBoe. The six month moratorium within the NTL has moved three wells, the two at the Telemark Hub and the one at the Canyon Express Hub, from ATP’s 2010 production profile. These wells were scheduled for production in the second half of 2010. Based on its revised development program, ATP expects to produce 9.0 MMBoe to 10.0 MMBoe for 2010.

As a result of the NTL, ATP’s preliminary estimate is that $50 million to $100 million of CAPEX will be eliminated from CAPEX in 2010. While the additional costs that must be incurred as a result of the NTL are under review, ATP estimates these costs to be approximately $30 million. ATP will seek to keep these costs as low as possible and will also seek reimbursement, transfer or sharing of these costs from other parties.

All information and projections in this press release are based on the May 30, 2010 6:52 pm CDT NTL and assumptions made by ATP as of the date of this release. New and revised NTL’s, announcements by the White House or other government agencies could cause modifications or adjustments.

About ATP Oil & Gas Corporation

ATP Oil & Gas is an international offshore oil and gas development and production company with operations in the Gulf of Mexico and the North Sea. The company trades publicly as ATPG on the NASDAQ Global Select Market. For more information about ATP Oil & Gas Corporation, visit www.atpog.com.

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. During December 2008, the SEC issued the final rule, "Modernization of Oil and Gas Reporting” and we have adopted it as of December 31, 2009. Those new regulations allow, among other things, disclosure of probable and possible reserve quantities in reports filed with the SEC. While we do not file such reserves, we occasionally will include them in presentations and discuss such reserves publicly. We and our independent third party reservoir engineers use the term "probable” to describe volumes of reserves potentially recoverable through additional drilling or recovery techniques that, by their nature, are more speculative than estimates of proved reserves. All estimates of reserves in this news release have been prepared by our independent third party engineers. More information about the risks and uncertainties relating to ATP's forward-looking statements is found in our SEC filings.