Set on demand cement

1 . A method of cementing a wellbore, the method comprising:

injecting into the wellbore a cement slurry comprising:

an accelerator composite having a shell encapsulating a core comprising an accelerator and a disintegrating agent, the disintegrating agent comprising a phase change material;

a cementitious material; and

an aqueous carrier; and

releasing the accelerator from the accelerator composite, wherein releasing the accelerator comprises breaking the shell by heating the disintegrating agent to cause the phase change material to expand,

wherein the core comprises the phase change material, and the phase change material comprises at least one of an inorganic salt, an eutectic mixture of inorganic salts, an eutectic mixture of an inorganic salt with an organic material, or a hydrate of an inorganic salt.

2 . The method of claim 1 , wherein the cement slurry further comprises an aggregate.

3 . The method of claim 1 , wherein the shell comprises at least one of alginate, cellulose, starch, chitosan, dextran sulfate, pectin, xanthan gum, a polymethacrylate, a polydimethylsiloxane, a polystyrene, a polyvinyl acetate, a polyvinylpyrrolidone, silica, alumina, titania, sodium silicate, calcium carbonate, nickel, nickel phosphorus, a nickel alloy, an iron oxide, an oxyhydroxide, or an iron salt.

4 . The method of claim 1 , wherein the accelerator comprises at least one of an alkali metal salt, or an alkali earth metal salt.

5 . The method of claim 1 , wherein the accelerator comprises at least one of sodium meta silicate or calcium chloride.

6 . The method of claim 1 , wherein the accelerator composite is present in an amount of about 0.5 wt. % to about 10 wt. %, based on the total weight of the cementitious material.

7 . A method of cementing a wellbore, the method comprising:

injecting into the wellbore a cement slurry comprising:

an accelerator composite having a shell encapsulating a core, wherein the core comprises an inner core of an accelerator, and an outer core of a disintegrating agent disposed between the inner core and the shell, the disintegrating agent comprising a phase change material;

a cementitious material; and

an aqueous carrier; and

releasing the accelerator from the accelerator composite, wherein the core comprises the phase change material, and the phase change material has a phase transition temperature of about 125° F. (52° C.) to about 1,000° F. (538° C.); and a volumetric expansion of at least 3% during a phase transition relative to a volume of the phase change material before the phase transition,

wherein the phase change material comprises a hydrate of an inorganic salt configured to expand in volume during a phase transition and to release water that generates additional pressure upon vaporization when heated above its boiling point.

8 . The method of claim 7 , wherein the accelerator comprises at least one of an alkali metal salt, or an alkali earth metal salt.

9 . The method of claim 7 , wherein the accelerator comprises at least one of sodium meta silicate or calcium chloride.

10 . The method of claim 7 , wherein the accelerator composite is present in an amount of about 0.5 wt. % to about 10 wt. %, based on the total weight of the cementitious material.

11 . A method of cementing a wellbore, the method comprising:

injecting into the wellbore a cement slurry comprising:

an accelerator composite having a shell encapsulating a core, wherein the core comprises an inner core of an accelerator, and an outer core of a disintegrating agent disposed between the inner core and the shell, the disintegrating agent comprising a phase change material;

a cementitious material; and

an aqueous carrier; and

releasing the accelerator from the accelerator composite, wherein the accelerator composite further comprises a magnetic material,

wherein the phase change material comprises a hydrate of an inorganic salt configured to expand in volume during a phase transition and to release water that generates additional pressure upon vaporization when heated above its boiling point.

12 . The method of claim 11 , wherein the method further comprises applying an electromagnetic radiation to the magnetic material to generate heat.

13 . The method of claim 11 , wherein the accelerator comprises at least one of an alkali metal salt, or an alkali earth metal salt.

14 . The method of claim 11 , wherein the accelerator comprises at least one of sodium meta silicate or calcium chloride.

15 . The method of claim 11 , wherein the accelerator composite is present in an amount of about 0.5 wt. % to about 10 wt. %, based on the total weight of the cementitious material.