ATP Oil & Gas Corporation engages in the acquisition, development, and production of oil and natural gas properties in the Gulf of Mexico, the United Kingdom, and the Dutch Sectors of the North Sea. As of December 31, 2009, it had estimated net proved reserves of approximately 135.2 million barrels of crude oil or other liquid hydrocarbons equivalent (MMBoe), of which approximately 91.3 MMboe were in the Gulf of Mexico and 43.9 MMBoe were in the North Sea. The company also owned leasehold and other interests in 62 offshore blocks and 104 wells, including 19 subsea wells in the Gulf of Mexico, as well as had interests in 11 blocks and 3 company-operated subsea wells in the North Sea. It had reserves of approximately 77.9 million barrels of crude oil or other liquid hydrocarbons and 343.3 billion cubic feet of natural gas. The company was founded in 1991 and is based in Houston, Texas.