METHODS AND COMPOSITIONS OF CONTROLLING THE RHEOLOGY OF A DIUTAN-CONTAINING WELL TREATMENT FLUID AT HIGH TEMPERATURES

摘要

The invention provides a method for treating a subterranean formation penetrated by a wellbore, the method comprising the steps of formulating a treatment fluid and introducing the treatment fluid through the wellbore. The treatment fluid comprises water; diutan; and a sufficient amount of salt to increase the density of the treatment fluid to at least 8.5 lb/gal, wherein at least 50% by weight of the salt is selected from the group consisting of: bromide salts, non-bromide salts having a higher salting-in effect than bromide according to the Hofmeister series as measured by the salt's effect on the cloud point of poly(ethylene oxide) that has a molecular weight of 4×10⁶, and any combination in any proportion thereof. The invention also provides a treatment fluid for use in a subterranean formation penetrated by a wellbore, the treatment fluid comprising: water; diutan; and a sufficient amount of salt to increase the density of the treatment fluid to at least 8.5 lb/gal, wherein at least 50% by weight of the salt is selected from the group consisting of: bromide salts, non-bromide salts having a higher salting-in effect than bromide according to the Hofmeister series as measured by the salt's effect on the cloud point of poly(ethylene oxide) that has a molecular weight of 4.10⁶, and any combination in any proportion thereof.