By Jordan Blum From Houston Chronicle

Offshore driller Noble Corp., which primarily operates out of Sugar Land, abruptly announced the retirement of longtime CEO David Williams, who’s immediately replaced by Executive Vice President Julie Robertson.

Robertson, 62, has worked at Noble Corp. and its subsidiaries for more than 40 years. She joins a small group of female CEOs in the male-dominated energy sector, including Occidental Petroleum’s Vicki Hollub, Oil States International’s Cindy Taylor, Sempra Energy’s Debra Reed and Duke Energy’s Lynn Good.

Noble, which is formally domiciled in London, struggled during the oil bust and in its aftermath as the offshore sector continues to flounder. The company, however, has maintained its position as one of the leading offshore drillers worldwide.

Robertson, a University of Texas graduate, was appointed to the board directors in September, setting up her promotion this week. Robertson had served as an executive vice president over human resources and more since 2006.

Robertson is a natural choice for Noble, which prizes its internal culture, said Byron Pope, an energy analyst with the Houston investment banking firm Tudor, Pickering, Holt & Co. Another option would have been Chief Financial Officer Adam Peakes, but he has only been with the company for a year, Pope said.

Although Williams, at 60, is about two years younger than Robertson, industry analysts said it makes sense for him to move on after 10 years of leading Noble, which included bringing the company through the oil crash. Other chief executives who survived what was the worst oil industry downturn in a generation, have also stepped aside, including those of major offshore drillers like Transocean, Ensco, Diamond Offshore and Rowan Cos.

“We’ve seen a transition over the last few years in offshore drilling with old leaders moving on,” Pope said.

Noble Vice President Jeffrey Chastain said Williams had discussed retiring with the corporate board for a few months and felt the time was right with a strong management team in place. Williams will serve in an advisory role through February.

Noble Corp. was formed in 1985 after it was spun out of Noble Affiliates, now Houston’s Noble Energy. Noble Corp. moved to the Houston area from Oklahoma in 1989 and still makes its home in Sugar Land, even though its formal headquarters is international. Noble moved its headquarters in 2002 to the Cayman Islands for tax purposes. Noble has shifted its domicile to Switzerland and then to the United Kingdom.

Noble Corp. employs about 2,500 workers worldwide, including more than 300 in the Houston area.

Praveen Narra, an energy analyst at the financial services firm Raymond James in Houston, said the shakeout in the offshore sector isn’t over yet. She expects the industry, which has seen several mergers in recent years, including Ensco’s acquisition of Houston’s Atwood Oceanics and Transocean’s takeover of Songa Offshore of Norway, to consolidate further.

“There’s quite a lot of rigs going after the same work,” Narra said.

If Noble Corp. wants to pursue its own deals, it would have wrap up a lawsuit brought by the Houston offshore driller Paragon, which emerged from bankruptcy last year as a private company. Paragon was spun off from Noble in 2014, and Paragon claims it was loaded up with debt and set up to fail. Noble denies those allegations.

Noble Corp. stock gained 15 cents a share, or 2.7 percent, to close at $5.77 Friday.

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