The World's Youngest Oil Tycoon Just Lost His Billionaire Ranking

In May, oil executive Brian Sheffield became the only self-made billionaire under 40 on Bloomberg's Billionaire index who didn't come from a tech background. Sadly for him, it didn't last long.

The recent drop in oil prices has already dragged him back down to the ranks of the multi-millionaires, Bloomberg reported.

Sheffield grew up in Texas in an oil family. His father worked for Parker & Parsley Petroleum and later for Pioneer Natural Resources.

But, according to Bloomberg, young Bryan wanted to work in finance and moved to Chicago to trade futures.

He never made more than $100,000 a year - even when he was living on the Spanish coast and trading German bonds in Gibraltar, Bloomberg reported.

So he moved back to Texas to learn the family business.

Soon, he began to build his own drilling company, Parsley Energy. It was 2009, right when fracking - or hydraulic fracturing, which uses hydraulically pressurized chemicals to fracture oil-rich rock bases - was starting to take hold as a popular drilling technique.

Things took off for Sheffield, and he earned his billionaire ranking in May 2014, when he took his company public.

But today, benchmark crude futures have fallen to around $75 a barrel, according to Bloomberg - well below the $90 mark where they've hovered the past few years.

Parsley's shares, of which Sheffield holds more than 14 percent, have dropped about 10 percent below their $18.50 IPO price.

But who knows, at the rate this guy is going, he could be rolling in the deep again in no time.