For deeper deposits, volumes of superhot pressurized steam are pumped underground to melt out the bitumen so it can be sucked up to the surface by production wells running in parallel. (scientificamerican.com)
And he points out that foam doesn't just clean oil up; it can also produce it cleanly by helping to drag raw crude out of deep deposits. (discovermagazine.com)
Oil companies used to avoid salt, sometimes drilling around it to reach deep deposits. (discovermagazine.com)