Inhibiting Salting Out of Diutan or Scleroglucan in Well Treatment

A fluid viscosified with diutan or scleroglucan is provided for use in a well, the fluid including: (i) water; (ii) one or more salts selected from the group consisting of alkali metal halide salts, alkaline earth metal halide salts, and any combination thereof; (iii) a viscosifier selected from the group consisting of diutan, a diutan derivative, scleroglucan, a scleroglucan derivative, and any combination thereof; and (iv) a delayed-release source of a weak acid; wherein the initial pH of the fluid is at least 6. In addition, a method of treating a portion of a well includes the steps of: (A) forming such a fluid; and (B) introducing the fluid into the portion of the well. The fluid has rheological properties that can be adapted, for example, to well treatments such as gravel packing at higher temperature and in higher density brines while avoiding salting out of the viscosifier.