There's trillions of tons of coal, trillions of barrels of oil, trillions of cubic meters of natural gas. It ain't depleting centuries from now. By the 2500s people will be starting to use oil on Titan. Titan has hundreds of times the oil on Earth.
This Tiny Moon Has More Oil & Gas Than Earth
Imagine a place with hundreds of times more natural gases and other liquid hydrocarbons than all of the known oil and gas reserves on our bountiful planet. As it turns out, that place is a comparatively small, smoggy and perpetually drizzly moon in our very own solar system, happily orbiting around Saturn.
https://oilprice.com/Energy/Energy-General/This-Tiny-Moon-Has-More-Oil-Gas-Than-Earth.html