The bosses of some of the world’s biggest oil companies said crude prices are likely to keep rising because a lack of investment will curtail future supply.

The chief executive officers of Royal Dutch Shell Plc and TotalEnergies SE joined major commodity traders and banks in predicting that oil could go as high as $100 a barrel, although they also said volatile markets could drive prices back down again.

Low investment is “going to exacerbate supply and demand tightness as the economies pick back up again, and then in time we’ll see supply pick up and rebalance,” Exxon Mobil Corp. CEO Darren Woods said at the Qatar Economic Forum Tuesday. “In the shorter term, probably, higher prices” are more likely.

Trading house Trafigura Group said oil could top $100 a barrel over the next year. Bank of America Corp. also forecast this week that prices could jump to that level and Goldman Sachs Group Inc. said it doesn’t rule it out. West Texas Intermediate crude has climbed more than 50 per cent this year as widespread vaccinations increase mobility and boost demand. Benchmark Brent crude is up 46 per cent to more than $75 a barrel, the highest in around 2-1/2 years.

Global oil markets had one of the most turbulent years in history last year with the coronavirus pandemic sending prices crashing. But economies in the West are growing again, roads in Europe and the U.S. are more congested, and greater numbers of Americans are flying. While that could drive prices higher in the near term, the energy transition means oil consumption could start to plateau and eventually decline.

The energy shift means there hasn’t been enough investment in oil and gas projects and that could push prices higher, Qatari Energy Minister Saad al-Kaabi said at the same event. BP Plc CEO Bernard Looney said earlier Tuesday that rising crude is helping the company’s energy transition plans and generating better cash flow and returns for shareholders.

There’s “quite a chance” of reaching $100 a barrel, “but we could see again in coming years some low prices,” TotalEnergies CEO Patrick Pouyanne said. “We’ve been accustomed to volatility.”