Devon Energy Corp., one of the most active drillers in the Tuscaloosa Marine Shale, said Thursday it will close its Houston office in a cost-cutting move, putting all of its U.S. personnel into a single operations group at the firm’s Oklahoma City corporate headquarters.

Devon will transfer the operational responsibilities for its assets in Louisiana, south Texas and east Texas to Oklahoma City. Devon said the move will save the company around $80 million a year. The savings will come from lower general administrative expenses and reduced personnel costs.

Devon said a number of workers will be relocated, and the change should be complete by March 31.

The company expects the reorganization to cost $125 million, with $100 million of that charge in the fourth quarter. The remaining costs will be spread out over the first half of 2013.