Plugging high permeability earth strata

Abstract From the Canadian patent

Abstract of the Disclosure, A method is provided allowing close control of the steam back pressure in a highly permeable formation during the temporary plugging of the formation using foam produced by introducing steam and a foaming agent into the formation forming a foam having a steam as its gaseous phase which collapses upon condensation of the steam. The method comprises intermittently interrupting the steam flow into the formation to inject a slug of surfactant dissolved or dispersed in a solvent such as water oil or, alcohol.