Patterson-UTI Energy Inc. has promoted its chief operating officer to CEO because its chief executive, Douglas Wall, is retiring.

The oil and natural gas driller said late Friday that COO William Hendricks will take over on Oct. 1.

Wall became CEO in October 2007. Before joining Patterson-UTI earlier that year, he was an executive at oilfield services company Baker Hughes Inc.

Hendricks became Patterson-UTI’s COO in April. He had been an executive with services provider Schlumberger Ltd.

Also on Friday, the company said that it named Michael Conlon to its board. Conlon is a former partner of the law firm Fulbright & Jaworski LLP.

In afternoon trading Monday, Patterson-UTI shares fell 23 cents, or 1.3 percent, to $17.23.