ATP Oil & Gas Corporation (NASDAQ: ATPG) today announced that it has closed the previously mentioned $100 million temporary overriding royalty interest transaction at its Clipper property. Located at Green Canyon 300 in the deepwater Gulf of Mexico, Clipper has two wells that were completed in 2011 and tested at a combined rate of 22 MBoe/d (16 MBoe/d net to ATP), 62% oil. The new $100 million transaction is designed to fund a portion of the capital program at Clipper. Overriding royalty interest payments will not occur until Clipper begins producing. Clipper is scheduled to commence production late 3Q 2012 or early 4Q 2012. On Friday, March 16, 2012, ATP increased its First Lien facility by $155 million and the interest rate was reduced from a fixed 9.00% to a floating 8.75% per annum. These transactions are in addition to the approximately $80 million of asset monetizations that closed earlier this month. In total, ATP has improved its liquidity by closing transactions totaling approximately $335 million during March 2012. About ATP Oil & Gas Corporation ATP Oil & Gas is an international offshore oil and gas development and production company focused in the Gulf of Mexico, Mediterranean Sea and 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 contain "forward-looking statements" within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934. ATP cautions that assumptions, expectations, projections, intentions, plans, beliefs or similar expressions used to identify forward-looking statements about future events may, and often do, vary from actual results and the differences can be material from those expressed or implied in such forward looking statements. Some of the key factors which could cause actual results to vary from those ATP expects include, without limitation, volatility in commodity prices for crude oil and natural gas, the timing of planned capital expenditures, availability of acquisitions, uncertainties in estimating 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 ability to access them, and uncertainties regarding environmental regulations or litigation and other legal or regulatory developments affecting its business. ATP assumes no obligation and expressly disclaims any duty to update the information contained herein except as required by law. More information about the risks and uncertainties relating to ATP's forward-looking statements is found in the company's SEC filings or website, www.atpog.com.