Saudi Aramco plans to invest some $300 billion in the coming decade to maintain its oil production capacity, and pursue a large exploration and production program centering on conventional and unconventional gas resources, President and Chief Executive Officer Amin Nasser said.

The outlook for oil supplies is “increasingly worrying,” with about $1 trillion in investments lost during the current industry downturn and fewer new deposits being discovered, Nasser said at a conference in Istanbul.

Some estimates suggest that at least 20 million barrels a day of new output is needed over the next five years to offset rising oil demand and the natural decline of developed fields, he said.

The petroleum industry will be at the heart of global energy for years, and the transition to use of alternatives will be “long and complex”. The state-run company known formally as Saudi Arabian Oil Co., the world’s biggest oil exporter, boosted production to an annual record last year before the kingdom led the Organization of Petroleum Exporting Countries and other producers to curb output to stem a global glut. Aramco is also at the heart of the nation’s long-term strategy to wean its economy off oil. The government plans to sell about 5 percent of the company in 2018 in what could be a record IPO.

Saudi Arabia is also committed to developing solar energy and other renewable sources, and the economic restructuring strategy foresees the nation’s becoming “nothing less than a solar powerhouse”, Nasser also said.