Controlled release solid scale inhibitors

A method of inhibiting scale formation in a subterranean petroleum formation, the method comprising:

• mixing a scale inhibitor composition with a proppant to form a mixture;
• and
• injecting the mixture under pressure into hydraulically generated fractures of a wellbore, the scale inhibitor composition comprising a reaction product of a combination comprising from about 20 to about 55 wt. % of a phosphorus-containing compound, about 1 to about 20 wt. % of a calcium-containing compound, about 1 to about 15 wt. % of a magnesium-containing compound, water, and from 11 to about 25 wt. % of a sodium- or potassium-containing base, based on the weight of the combination, the reaction product being in the form of a substantially amorphous glass, and the combination being substantially free of liquid hydrocarbon, and wherein the sodium- or potassium-containing base comprises sodium hydroxide, potassium hydroxide, trisodium phosphate, sodium carbonate, potassium carbonate, potassium bicarbonate, sodium bicarbonate, potassium acetate, sodium acetate, sodium benzoate, or a combination thereof;
• the phosphorus-containing compound and the sodium- or potassium-containing base being in a weight ratio of from 5:1 to 2:1,
• wherein the substantially amorphous glass is particulate and has a particle size of from about 10 to about 30 mesh and whereby scale formation in the subterranean petroleum formation is inhibited.