the core however the permeability can be restored and even substantially increased by treatment with steam containing ammonium carbonate thus a well treated in this manner is stimulated a treatment according to this invention commonly increases the permeability of a fines containing formation at least 50 percent often at least 150 percent and in this instance 330 percent of the base permeability there is injected into another one inch diameter 2 7 inch long core from the same well a 3 percent by weight aqueous solution of sodium chloride at ambient temperature and 15 p s i for 3 75 hours at flow rates starting at 17 2 mls min and dropping to 12 2 mls min as the permeability stabilizes this establishes a base permeability of 223 mds next an aqueous solution containing 32 grams per liter ammonium carbonate is injected through the core at ambient temperature and 15 psi for 3 hours at a flow rate starting at 6 8 ml min and stabilizing at 4 7 ml min the permeability drops to 40 percent of the base permeability to the sodium chloride solution next there is added to boiler feedwater 32 g 1 of ammonium carbonate steam is generated and injected into the core at 500 u00b0 f and 700 p s i back pressure for 2 hours at a flow rate of 2 mls min for the next 2 hour period the treatment is the same except the concentration of.