"Millions of years ago, algae and plants lived in shallow seas. After dying and sinking to the seafloor, the organic material mixed with other sediments and was buried. Over millions of years under high pressure and high temperature, the remains of these organisms transformed into what we know today as fossil fuels.I don't think they are. Because if they are, we have bigger problems than running out of gas. Everyone would die overnight because there would be no more plastic, something widely used and completely necessary in medical devices. Plumbing, cooking, the roads we drive on, sex lube, caulk, cell phones.
Then you look at the fact that 5 million homes in the US alone use home heating oil as a heat source in the winter. Without home heating oil, millions would die every winter. There is no gas, and asking most of those people to heat with wood would be very difficult. Converting to electric heat would be obscenely expensive, both for the conversion and and for the actual heating.

Petroleum
Petroleum, or crude oil, is a fossil fuel and nonrenewable source of energy.

"Do we have 100 years of oil left?
World Oil Reserves
The world has proven reserves equivalent to 46.6 times its annual consumption levels. This means it has about 47 years of oil left (at current consumption levels and excluding unproven reserves)."

World Oil Statistics - Worldometer
Amount of Oil left in the world based on proven gas reserves and current global consumption levels. World Oil reserves, production, and consumption by year and by country, imports, exports, charts and list.

When we pump the oil reserves dry there will not be any more oil. Oil will be like Dinosaurs something that used to exist.