The world has, according to the latest estimates, oil reserves for a total of about 142 billion tons and natural gas reserves of 150 trillion cubic feet.

If humanity continues to consume oil with the current annual rate (about three and a half billion tons), and is not were other one, the reserves would last more than forty years.
Those of methane, however, would last a little 'more, more than sixty years.

In fact, if you consume more than two trillion cubic meters a year. Italy consumes each year 93 million tons of crude oil and 63.8 billion cubic meters of natural gas.