Exxon Mobil said it added to its portfolio in the Permian shale basin in Texas in exchange for a portion of its field operations in California.

Exxon under the terms of a non-monetary exchange with LINN Energy gets 17,000 net acres in the Permian basin in exchange for 500 acres at its Belridge field in California.

Permian production increased 58 percent from 2007 to reach 1.35 million barrels per day last year, which represents 18 percent of total U.S. crude oil production. Exxon said the Belridge field is producing approximately 3,400 bpd.

The Permian area will be operated by Exxon's subsidiary XTO Energy Inc.

"We continue to expand our leasehold position in a prolific area that is poised for profitable volumes,"

Randy Cleveland, president of XTO Energy, said in a Thursday statement.

For LINN, it said it would examine 300 potential future drilling locations in a California basin it says holds approximately 27 million barrels of oil equivalent.