Controlling chlorite or hypochlorite break rate of well treatment fluids using magnesium or calcium ions

A method of treating a subterranean formation penetrated by a well, the method comprising the steps of:

• (a) forming a treatment fluid comprising:
• 1) water having a magnesium ion concentration of less than 1 mM and a calcium ion concentration of less than 2.5 mM;
• 2) a water-soluble polysaccharide capable of increasing the viscosity of the water and present in a sufficient concentration to increase the viscosity of the water;
• and
• 3) a breaker comprising at least one member selected from the group consisting of a source of chlorite ions and a source of hypochlorite ions, wherein the breaker is present in a sufficient concentration to break the viscosity of the treatment fluid after introduction of the fluid into the subterranean formation;
• (b) at any stage of forming the treatment fluid, adding a breaker moderator comprising at least one member selected from the group consisting of a source of magnesium ions and a source of calcium ions to provide a sufficient concentration of the breaker moderator to reduce the break rate of the fluid compared to the treatment fluid without the addition of the breaker moderator;
• and
• (c) introducing the treatment fluid into the well and into contact with the formation.