Compositions and methods for filter cake removal

A method of removing filter cake from a subterranean borehole, said method comprising:

• drilling a borehole with a drill-in fluid to form a filter cake;
• contacting the filter cake with a composition comprising (a) an encapsulated persulfate;
• and (b) a nonionic surfactant;
• and (c) an unencapsulated persulfate, wherein the encapsulated persulfate is present in an amount from about 0.01 to about 20 weight percent, the nonionic surfactant is present in an amount from about 0.01 to about 50 weight percent, and the unencapsulated persulfate is present in an amount from about 0.01 to about 20 weight percent, based on the total weight of the composition, when the composition is introduced into the borehole;
• and
• allowing the composition to remain downhole for a period of time sufficient to degrade the filter cake;
• wherein the contacting the filter cake with the composition generates acidic conditions, without addition of an acid;
• and
• wherein the persulfate chemically breaks down the filter cake via direct oxidation or free radical oxidation.