Oil and gas will remain key energy sources despite the presence of shale and other alternative energy resources, the president of oil and gas company BHGE told CNBC on Monday.

“When you look at the energy requirements, the increasing population, we feel there’s going to be a necessity from an oil and gas perspective as we go forward,” Lorenzo Simonelli told CNBC on the sidelines of the World Petrolum Congress in Istanbul.

“LNG (Liquefied natural gas) continues to grow at 3 to 4 percent, oil continues to grow at about 1 percent, you’ve got natural gas growing at 2 percent, as you look long term that supply demand balance is going to be there. What we’ve got to focus on is making sure that we drive productivity through that value chain to let the investments go forward,” he added.

Oil and gas firms worldwide have cut their share in investment given the subdued market prices in the last few years. Wood Mackenzie, an energy consultancy, said in May that it expects exploration spending to increase by no more than 10 percent from the recent historic lows.

Given the low level of investments, the world could soon face an oil supply shortage, Amin Nasser, the chief executive of Saudi Aramco, said Monday also in Istanbul, Reuters reported. He added that it is too early to know if other energy resources such as shale gas will be able to develop at a fast enough pace to replace oil and gas.