(Repeats story published on Friday with no changes)
By Liz Hampton and Nia Williams
HOUSTON/CALGARY, March 3 (Reuters) - Doug Lucas stood outside a Houston energy conference early one morning last month handing out resumes and hoping to catch the eye of oil executives with a hand-written sign advertising "Petroleum Eng. Hungry for job interview."
Cut from oilfield services firm Halliburton Co in 2015, the 26-year-old temporarily turned to lawn care and cable-TV sales jobs while finishing a master's degree in petroleum engineering at the University of Southern California.
Despite relying on a depression-era sign for introductions, he is hopeful demand for petroleum professionals will come back.
"It's way better now than it was six or eight months ago," he said optimistically, as he solicited business cards from convention goers.
After a rout that began in 2014 due to a worldwide glut of oil in part caused by a U.S. shale boom, crude prices have rebounded from 13-year lows hit a year ago and have held above $50 a barrel since the start of the year when major oil producers curbed output as part of a global deal.
The higher prices have spurred an uptick in drilling activity as energy companies boost spending plans to take advantage of the crude price recovery.
However, massive cuts that cost some 440,000 jobs globally at energy companies in the last two years have left veteran workers and skilled job-candidates without a clear future in oil and gas.
Unable to find work in their chosen field, some have turned their sights to technology or other industries, adding a note of uncertainty to next week's CERAWeek industry conference in Houston.
The outflow of experienced workers and a lack of hiring as oil companies drive to become more efficient could put future production growth in jeopardy, should a nascent upturn in the industry accelerate, say experts. In western Canada, companies resuming production of crude oil are struggling to rehire rig crews following job and pay cuts.
A University of Houston global survey of laid off oil workers found that 25 percent had already moved to another industry and another 55 percent were considering it. Only 13 percent of those polled in late 2016 had found energy jobs.
"A good number of people are 'lost' to other industries," said Christiane Spitzmueller, the study's principal investigator. "This will translate into high recruitment and training costs for new hires."
The combined U.S. and Canadian rig counts, which can be an indicator of the health of the industry, jumped to 1,091 by Friday from 618 a year ago, a sign of the upturn in drilling in North America.
In western Canada, where many more rigs are working this year than last, drillers say a lack of experienced employees could slow their work later this year - or force them to pay higher salaries to lure workers back.
Dan Block, chief executive of Edmonton-based Jomax Drilling (1988) Ltd, said contractors he once employed took jobs in other industries, including construction.
"We are scrambling to bring people back," Block said.
Halliburton, an oil services firm that had about 50,000 employees at the end of 2016, down from more than 80,000 two years earlier, is now holding job fairs in regions where there is an uptick in drilling activity, such as Colorado, Texas, New Mexico, Oklahoma, and Ohio, the company said.
"We're seeing a good balance of both experienced and entry level candidates," said spokeswoman Emily Mir, noting that there is strong applicant interest in open positions in the Permian Basin - one of the hottest drilling areas in the United States due to its favorable economics.
The U.S. oil and gas industry will need to fill 1.9 million new jobs through 2035, according to consultancy IHS Markit .
But filling those jobs could prove a challenge, management consultancy KCA said in study published in September.
"A rapid run-up is going to be a really difficult spot for the industry, versus a slow ramp up where you can start to lure people back over time," said David Skinner, KCA's chief executive.
The study by KCA, Pink Petro and Glexnet, which polled 1,000 laid off and working energy professionals, found that 45 percent of executives or board members said they were ready to seek other job options, retire or are unsure what they will do post-downturn.
Karsten Thompson, petroleum engineering department chair at Louisiana State University (LSU), said the loss of experienced executives will hurt the training of professional staff.
"Students will miss out on mentorship," he said in an interview.
If experienced workers are less inclined to stay through another economic cycle, younger workers may already be placing bets on other careers. Before oil prices crashed, the University of Texas placed more than 90 percent of students who majored in petroleum engineering into oil and gas jobs. In 2015 and 2016, that number fell by around a quarter.
LSU said its May 2016 engineering graduates reported fewer than 50 percent had found jobs, down from around 63 percent in 2013.
"In the past, for students with petroleum engineering jobs who couldn't find full time work, there were always opportunities to work offshore as a roustabout," said Trey Truitt, Associate Director for Employment Services at LSU.
"In this economy, those jobs haven't been available either."
Despite a potential shortage of engineers, companies could still grow their businesses using existing staff augmented with newer technology and contract labor, said KCA.
Automation and technologies that require more software know-how are changing the skills needed by industry workers.
"Someone who majors in petroleum engineering with a minor in computer science, that might be the ideal engineer going forward," said John Graves, of energy consultancy Graves & Co.
Viet Pham, 23, a 2015 graduate from University of Texas at Austin's Petroleum Engineering program said if he could do it all over again, he would have majored in mechanical engineering or computer science.
Pham, who has been working at a retailer, is taking engineering courses at a community college to expand industry contacts and improve his professional job prospects.
"Petroleum is volatile," he said. "It's great when it works."
Additional reporting by Ruthy Munoz in HOUSTON; Writing by Gary McWilliams; Editing by Simon Webb and Marguerita Choy