American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.
Two new high viscosity water base fluids have been developed for use as spearheads to acidizing treatments and as fracturing fluids used in the placement of proppants. Both fluids are derived from proppants. Both fluids are derived from the same basic chemistry and are completely solid-free. One fluid is designed for high temperature applications (wells with formation temperatures ranging from 220 to 325 deg. F), while the other is for the more prevalent low temperature wells (80 to 220 deg. F). prevalent low temperature wells (80 to 220 deg. F). Using these fluids, proppant concentrations up to and including ten pounds per gallon have been successfully placed into fractures.
The basic advantage to using solid-free fracturing fluids lies in minimizing the permeability damage to both the formation and permeability damage to both the formation and packed fracture. This damage is caused by packed fracture. This damage is caused by solids found in polymers used to impart viscosity to a fracturing fluid, or in the fluid loss additives which help control fluid leakoff. Previous systems that used solid-free polymers were characterized by less than desirable fluid loss control and often required significant amounts of a fluid loss additive. Use of a fluid loss additive meant that these systems were no longer solid-free and, depending upon the amount of additive, could cause significant damage. The two new fluids have achieved a solid-free status without sacrificing fluid loss control and therefore are not used in conjunction with a fluid loss additive. Permeability damage tests, in both cores and sand packs, were run on these new fluids. The results of these tests were cornpared to those obtained when fracturing systems, using other polymers or fluid loss additives, were examined.
This paper describes the underlying chemistry of the two solid-free fluids, their resulting fluid rheology and applications. Field mixing procedures are discussed as are well case histories. Special emphasis is placed on the treatment of high temperature placed on the treatment of high temperature wells in which the fluids were used either as a spearhead to an acid treatment or to carry and place high concentrations of propping agents.
