Self-repairing cement including microcapsule-in-microcapsule material and designed swellable rubber and methods for fabricating same

A method for forming a microcapsule encapsulated microcapsule (MIM) material for self-repairing cement, the method comprising:

• forming a water-in-oil emulsion containing an aqueous phase dispersed within a hydrophobic media continuous phase, wherein the aqueous dispersed phase comprises a mixture of polyol compounds, and wherein the continuous phase is comprised of a solvent;
• adding a mixture of a prepolymer and a dissolved isocyanate or liquid isocyanate compound to the water-in-oil emulsion;
• polymerizing the prepolymer in a first stage polymerization reaction with the polyol via interfacial polymerization to form a polymeric microcapsule shell, encapsulating the liquid polyol compound in the formed polymeric microcapsule and thereby producing a plurality of second microcapsules;
• forming a second water-in-oil-in-water emulsion, wherein the continuous phased is comprised of an aqueous solution, and wherein the dispersed phase is comprised of the water-in-oil emulsion comprising the produced plurality of second microcapsules;
• adding a second quantity of the prepolymer and the liquid isocyanate compound to an aqueous solution containing a surfactant;
• and
• adding a cross-linker to polymerize the prepolymer in a second stage polymerization reaction with the cross-linker via interfacial polymerization to form a larger polymeric microcapsule shell, encapsulating the liquid isocyanate compound and the plurality of second microcapsules in the formed polymeric microcapsule and thereby producing a plurality of first microcapsules.

A self-healing cement slurry comprising:

• cement;
• sand;
• water;
• and
• microcapsule encapsulated microcapsules (MIM) material comprising:
• a plurality of first microcapsules comprising a first core and a first shell;
• a plurality of second microcapsules that each comprise a second core and a second shell;
• wherein the plurality of second microcapsules are dispersed in a continuous phase within the first core of the first microcapsule,
• wherein both the first and second shell are comprised of a polyurethane cross-linked material;
• and
• wherein the cement slurry comprises the MIM material in an amount ranging from 1 to 50% by weight, relative to the entire weight of the cement slurry.