There are two proven, large scale methods of reforming oil.

Shale oil or Tar sand cracking.
    The oil is trapped in a mineral matrix near the surface, which can be mined. If you treat the sand/rock and oil mix correctly ( heat, mainly), it releases the oil. The Athrabasca tar sands are the only major example of this.

Coal reforming: Coal is partially burnt, under caontrolled conditions(Temprature, pressure, oxygen supply, etc), and the very long chain hydrocarbons in it are split into smaller lengths. This process was commonly used to produce petrol, or town gas.
The two major instances of petrol production via this method were apartheid era South Africa- oil embago, and Germany during WWII.


Neither method is that efficiant, so is not worth doing unless oil prices are high, or you gan't get oil any other way.