u201c bitumen u201d bitumen is classified as an extra heavy oil with an api gravity of about 10 u00b0 or less referring to its gravity as measured in degrees on the american petroleum institute api scale heavy oil has an api gravity in the range of about 22 3 u00b0 to about 10 u00b0 the terms viscous oil heavy oil and bitumen are used interchangeably herein since they may be extracted using similar processes u201c in situ u201d is a latin phrase for u201c in the place u201d and in the context of hydrocarbon recovery refers generally to a subsurface hydrocarbon bearing reservoir for example in situ temperature means the temperature within the reservoir in another usage an in situ oil recovery technique is one that recovers oil from a reservoir within the earth the term u201c formation u201d as used herein refers to a subterranean body of rock that is distinct and continuous the terms u201c reservoir u201d and u201c formation u201d may be used interchangeably the term u201c viscosity reducing injectant u201d means a fluid that is injected into the reservoir for reducing the viscosity of the in situ hydrocarbons for example the injectant may comprise steam water vaporized solvent liquid solvent or a combination thereof examples of recovery processes using such injectants are provided in the background section by replacing the round orifices of bacon which.