Encana Corp. is acquiring Athlon Energy Inc. for $5.3 billion in the largest-ever U.S.-Canada transaction in the exploration and production sector.

The all-cash deal, in which Calgary-based Encana would also assume Fort Worth-based Athlon’s debt for a total deal value of $7.1 billion, would bolster Encana’s current oil production by about the equivalent of 30,000 barrels of oil per day while adding about 140,000 acres of land around the Midland Basin to the company’s portfolio. The transaction is expected to close at the end of the year.