W&T Offshore Inc. plans to buy Callon Petroleum Co.’s shares of Gulf of Mexico oil and gas fields for $100 million.

Callon announced the sale Thursday. It’s supposed to close by Nov. 30.

Houston-based W&T will buy a 15 percent share of the Medusa field, which produces about 1,000 barrels of oil per day, and Callon’s 7.5 percent interest in the production facilities for the field.

Also included in the sale are 10 shallow-water fields that Callon doesn’t operate that produce about 5.1 million cubic feet of natural gas each day.

Chairman and CEO Fred Callon said the sale completes the company’s transition to one that only drills onshore and focuses on western Texas’ Permian Basin. Callon said the company will use the money to acquire or drill more wells.