WELL TREATMENT
Particles containing scale inhibitor may be made by contacting porous ceramic beads with a solution of scale inhibitor, and then drying the beads. If the dried beads are then contacted with a solution containing a high concentration of polyvalent cations, for example 2.5 M calcium ions, and then dried again, then the rate of release of scale inhibitor when the beads are subsequently contacted with water is reduced. Varying the concentration of the polyvalent cation in the range 0.1 to 5.0 M varies the rate at which the inhibitor is subsequently released. The beads may be used as fracture proppants or in a gravel pack so as to suppress scale formation in an oil or gas well.