• In all oil fields, oil is left behind after primary (oil production using reservoir energy) and secondary (oil displacement with water) operations.
  
• The amount of remaining oil ranges from 30% to 90%
  
• The industry has long attempted to access these large, residual volumes.  However, to do so requires changing the properties of the oil.
  
• The primary methods of doing this are:
  • Thermal:  add heat to oil to make it less viscous, so it flows easier through the rock pore spaces.
  • Hydrocarbon injection:  the injectant either acts like a solvent and "dissolves" the oil, or combines with the oil in such a way to make it flow easier.
  • CO2 flooding: this works by either displacing oil or combining with it in such a way to make it flow easier.
  • Chemical Flooding: the recovery enhancement mechanisms are similar to CO2 in that the slug of chemically treated water, either acts like a piston and pushes oil ahead of it as it moves through the formations, or it combines with the oil to chemically alter it to make it flow easier.