The deal includes two non-operated assets, Ram Powell, where it has 31% stake, and Diana Hoover, 33.33%.
Bob Dudley, BP group chief executive, said: "While these assets no longer fit our business strategy, the Gulf of Mexico remains a key part of BP’s global exploration and production portfolio and we intend to continue investing at least $4bn there annually over the next decade."
The deal is subject to regulatory approvals and the parties anticipate the deal closing by the end of 2012.
The company will not shift its focus on producing more high-margin barrels from fewer, larger assets in the Gulf of Mexico.
With the deal, BP has entered into agreements to sell assets with a value of more than $32bn since the beginning of 2010 and it expects to divest assets with a total value of $38bn between 2010 and 2013.
US-based Plains Exploration & Production Company (PXP) mainly develops and produces oil and natural gas in California, Texas, Louisiana, the Rocky Mountains and the Gulf of Mexico.
Image: Installation of the topsides on the Hoover Diana platform was carried out by the Saipem 7000 crane vessel.