The head of Saudi Arabia’s state energy giant has warned of a looming oil shortage as a $1tn drop in investments into future production takes effect. Amin Nasser, chief executive of Saudi Aramco, the world’s largest oil producing company, said on Friday that 20m barrels a day in future production capacity was required to meet demand growth and offset natural field declines in the coming years. “That is a lot of production capacity, and the investments we now see coming back — which are mostly smaller and shorter term — are not going to be enough to get us there,” he said at the Columbia University Energy Summit in New York. Mr Nasser said that the oil market was getting closer to rebalancing supply and demand, but the short-term market still points to a surplus as US drilling rig levels rise and growth in shale output returns. Even so, he said it was not enough to meet supplies required in the coming years, which were “falling behind substantially”. About $1tn in oil and gas investments had been deferred and cancelled since the oil downturn began in 2014.