The oil industry will need to shell out about $11 trillion over the next two decades to meet the world's growing appetite for crude, OPEC says in its annual outlook.

The cost of keeping the globe fueled up assumes that OPEC's vision for the future comes to pass. In that vision, oil demand continues to grow and crude still makes up the lion's share of the energy mix, even as more electric vehicles hit the road.

OPEC has warned for years that oil producers shouldn't get complacent about investing in future production. Spending on new output fell significantly in 2015 and 2016 during an historic oil price downturn.

"While investments picked up slightly in 2017 compared to the previous two years, and the expectations are for higher levels again in 2018, it is vital that as an industry we ensure there is timely and adequate investment so as not to lead to a supply shortage in the future," OPEC Secretary General Mohammad Barkindo said in OPEC's World Oil Outlook 2018

The report forecasts global oil demand will grow by 7.3 million barrels a day between 2017 and 2023, eventually hitting 104.5 million barrels a day. By 2040, OPEC sees the world consuming nearly 112 million barrels a day.