LARAMIE, Wyo. — Ashley Lantz had no idea what her major would be when she was a freshman at Colorado School of Mines, but she liked the idea of living in exotic places.

She decided on petroleum engineering. Now she's 23 and on the vanguard of the "Great Crew Change" as companies seek to replace an entire generation who entered the industry during the last oil boom.

With pay starting at $50,000 to $60,000 and a healthy supply of jobs — a result of booming natural gas drilling in Wyoming and other states, and of retirements in the profession — enrollment in undergraduate petroleum engineering is up 46 percent nationwide since 2002.

"Every company that I've talked to says they simply can't get enough petroleum engineering staff for their projects. They're just crying out for people," said Brian Towler, head of the Department of Chemical and Petroleum Engineering at the University of Wyoming.

The University of Wyoming is getting on board by bringing back the undergraduate petroleum engineering major after a four-year hiatus. Towler hopes eventually to have 100 undergrads, a figure not seen at the university since 1987.

Similarly, the 2,347 undergraduates majoring in petroleum engineering nationwide this school year is the highest figure since 1987 — though that's still well below the peak of 11,014 in 1983, according to figures that Texas Tech professor Lloyd Heinze has compiled for the Society of Petroleum Engineers.

It was Lantz's adviser who looked at her good math and science grades and suggested petroleum engineering. "Four years ago, they knew there was a huge age gap and that we would need people," Lantz said.

Though the profession offers plenty of opportunities for far-flung travel — with lots of oil and gas drilling in the former Soviet republics, west Africa and South America — Lantz said that heading overseas is no longer a priority for her.

Between her junior and senior years, she interned with EnCana, based in Calgary, Alberta. And last fall, months before her May graduation, the company offered her a job.

"Senior year was pretty nice knowing that I had a job," she said.

She is based in Denver, but does go one week a month to Parachute, on Colorado's Western Slope, where gas drilling is booming.

So far she has focused on the production side — working on existing wells — but she also plans to get to know the profession's other specialties, such as exploration and transforming newly drilled wells into producing wells.

"Every person you meet has a different story," she said. "It's pretty neat that with one degree you can do so many different things."

Even more opportunities will be available for the next generation of petroleum engineers, according to Margaret Watson, spokeswoman for the Society of Petroleum Engineers in Richardson, Texas. The average age of the organization's members is approaching 50, she said, and that means not only more openings, but also more opportunities to advance.

"These people are going to have to become up-to-speed very quickly and have to move into management positions more quickly than in the past because those vacancies are going to exist," she said.

A growing number of students seem to be aware of these developments.

Petroleum engineering enrollment is up for most programs that offer such degrees. Only the University of Southern California, with the nation's smallest undergraduate program, hasn't added students this year.

Texas Tech's program has grown by 53 students from last year, an increase of 22.4 percent; followed by Colorado School of Mines (51 students; up 23.9 percent), Oklahoma (50 students; up 31 percent) and Texas A&M (45 students; up 15.4 percent).

The largest programs are still in Texas: University of Texas-Austin (409), Texas A&M (338) and Texas Tech (290 students).

The University of Texas' program nearly doubled from 2002 to 2004, but it may have topped out. Mukul Sharma, a petroleum engineering professor at Texas-Austin, said the entrance requirements had been raised. "We have 17 faculty here, so our student-faculty ratios go completely out of whack if our student numbers go beyond 400 students," he said.

Another reason for being conservative with enrollment — if the job market cools, students enrolled today might find fewer prospects when they graduate. "If we try to match the industry's ups and downs, we will always be four years out of phase," Sharma said.

And more and more, this field is for the mathematically inclined. Towler said students should expect to take three semesters of calculus and one of differential equations. There are also courses in engineering science — statics, dynamics, fluids and thermodynamics — as well as in drilling, production, oil and gas reservoirs, and measuring the properties of rock.

"It's a lot more of a high-tech field — a lot more exotic materials being used — and it's a lot more math-intensive than it was previously," he said.