Method for time-controlled release of breakers by use of breakers encapsulated within membranes containing water soluble polymers

A method for assisting in removing filter cake in a subterranean formation containing an aqueous viscous fracking fluid comprising:

• a) exposing the filter cake to at least one breaker controllably released from within a capsule;
• b) wherein the capsule comprises an outer shell and the at least one breaker, which is encapsulated within the outer shell;
• c) wherein the outer shell comprises a mixture of water-insoluble polymers and water-soluble polymers, but contains no solid inorganic material;
• d) dissolving the water-soluble polymers of the outer shell with the aqueous viscous fracking fluid within the subterranean formation, thereby creating voids in the outer shell of the capsule through which the aqueous viscous fracking fluid comes into contact with and dissolves the at least one breaker;
• e) whereafter the dissolved at least one breaker is controllably released from the capsule, allowing the dissolved at least one breaker to diffuse outward from within the capsule;
• f) whereafter the released at least one breaker interacts with the filter cake, thereby dissolving the filter cake;
• g) thereby facilitating removing the filter cake from the subterranean formation;
• wherein the capsule, except for the voids created when the water soluble polymers are dissolved, remains intact during the release of the at least one breaker that is contained within the capsule.