Exxon Mobil Corp. is in talks to pay more than $250 a share for Pioneer Natural Resources Co., according to a person familiar with the matter.

An all-stock deal could be announced as soon as Wednesday, said people familiar with the matter, who asked to not be identified because it isn’t public. At more than $250 a share, the deal would value Pioneer at at least $58 billion, based on its outstanding share count, according to data compiled by Bloomberg.

A final agreement hasn’t been reached and the terms could change or talks could still end without a deal, the people said.

Representatives for Exxon and Pioneer declined to comment.

Pioneer rose 0.8% to close at $237.41 in New York trading Tuesday, giving the company a market value of about $55 billion. Exxon fell 0.4% to $110.45, for a market value of about $442 billion.

The deal would unite two of the biggest acreage holders in the Permian Basin of Texas and New Mexico, making Exxon far and away the formation’s biggest oil producer.

--With assistance from Gillian Tan and Mitchell Ferman.

Author: Liana Baker, Kiel Porter and Kevin Crowley