BY GUY CHAZAN

BP PLC’s $7 billion deal with Devon Energy Corp should help dispel some of the misgivings that have weighed on the British oil major’s stock in recent years”particularly doubts about its ability to keep pumping more and more oil.

The deal gives BP a foothold in the deep waters off the shores of Brazil, one of the world’s most prospective oil regions, and one that could turn into a major source of growth for the company in coming years.

BP announced Thursday it would pay Devon $7 billion in cash for its assets in Brazil, Azerbaijan and the deepwater part …