Patent ID: 7846877

Claim:
A method for treating at least a portion of a well, the method comprising the steps of: (a) forming a treatment fluid comprising an aqueous solution, wherein the aqueous solution comprises: (i) water; (ii) a water-soluble polysaccharide; (iii) one or more water-soluble salts, wherein the one or more salts are selected and are in at least a sufficient concentration such that the water-salt solution has a density of at least 10 ppg; and (iv) urea; wherein the concentration of the urea in the water is in at least a sufficient concentration such that the aqueous solution has a G′ of at least 2 Pa whereas an identical aqueous solution except with less than the sufficient concentration of the urea would not have a G′ of at least 2 Pa, and wherein G′ is measured in the linear viscoelastic region at least one desired temperature in the range of 10° C.-50° C. without any increase in temperature of the aqueous solution above the desired temperature; and (b) introducing the treatment fluid into the well.