Steam injection process for recovering heavy oil

A steam flood process for recovering heavy oil and water from the production stream of a producing formation, said process comprising:

• processing the production stream from the producing formation to separate water containing calcium magnesium compounds from said heavy oil;
• flowing said water into a mixing vessel;
• mixing sufficient sodium hydroxide with said water within said vessel to adjust the pH of the water to a value of from about 9.0 to about 10.5 while maintaining the temperature of the water in the range from about 140.degree. to about 210.degree. F. to thereby react with said calcium and magnesium compounds to form and precipitate insoluble calcium carbonate and magnesium hydroxide from said water to reduce the hardness of the water to a value of from about 10 to about 60 ppm;
• recirculating at least part of said insoluble calcium carbonate and magnesium hydroxide during said mixing;
• removing at least part of said insoluble calcium carbonate and magnesium hydroxide through one outlet of said vessel;
• removing said water through a different outlet of said vessel after its hardness has been reduced to from about 10 to about 60 ppm and flowing said water through a cation exchange resin to remove substantially all of the remaining calcium and magnesium from said water;
• generating steam from said water;
• and
• injecting said stream into said producing formation to heat said heavy oil therein.