OKLAHOMA CITY (AP) — Chesapeake Energy Corp. has announced the layoffs of about 400 employees, the vast majority at its headquarters in Oklahoma City.

The layoffs were announced Tuesday in an email to employees from Chesapeake CEO Doug Lawler.

Lawler says the layoffs are part of the company's continuing effort to "structure and position" itself for success.

The layoffs include about 330 employees in Oklahoma City. The remainder will be at company field offices in Louisiana, Ohio, Texas, Pennsylvania and Wyoming. That accounts for about 13 percent of the company's workforce.

The job cuts leave Chesapeake with a total of about 2,900 employees. About 1,800 of them are in Oklahoma City.

Lawler's email says employees affected by the layoffs will receive undisclosed assistance in "their personal and career transition."