Methane is the simplest hydrocarbon molecule; 1 carbon and 4 hydrogens. It’s a gas at room temperature. Natural gas is mostly methane with some percentage of the other gaseous carbon-hydrogen molecules; ethane, propane, butanes, pentanes, etc. Methane and natural gas is very, very common in the rocks and muds of the world. That said, the conventional reserves of natural gas, 6,254 trillion cubic feet, represent less total energy than the remaining proven reserves of oil.