While crude oil prices rose Monday amid escalating violence in Iraq, one portfolio manager sees a clear path to $150-a-barrel levels.

"It's a simple case of the world being able to cope with oil prices where they currently are, around $110 a barrel," Jonathan Waghorn of Guinness Global Energy Fund said.

"So, what we do is we think of oil being a cost of the global economy. Go back over 30 or 40 years, you see that cost has moved dramatically over time. Prices go too high, the world economy suffers. As we stands at the minute, the world oil prices, the budget as a total represents about 5 percent of world GDP. And we can see that the world appears to be coping with that pretty robustly."

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On CNBC's "Halftime Report," Waghorn said that $150 was a real possibility within the next six years.

"As the world economy continues to grow, let's say 3 percent real growth to the end of the decade, we'd expect oil prices to inflate alongside," he said. "Simple maths, really, it takes you to $150 at the end of the decade. To nominal terms, maybe that's $125 in real terms. It's still a pretty substantial uplift where we are today."

Waghorn also said that he remained positive on energy stocks.

"This is still an early trade for us in terms of this resurgence of the macro environment, and that being recognized in energy prices," he said. "We think they are very, very cheap on price/earnings, on price to cash flow, on sum-of-the-parts basis."

Guiness Global Energy Fund is an equal-weighted energy fund that counts Total, Newfield, Canadian Natural, Unit and Devon Energy among its holdings.

"But recently we've been adding some more European names into the portfolio," Waghorn added.

— By CNBC's Bruno J. Navarro. Follow him on Twitter @Bruno_J_Navarro.