The damage effect of a guar gum water-based fracturing fluid has been investigated on sandstone and limestone formations furnished by Cleveland Quarries Co. of Ohio. The permeability and porosity of each core was measured before treatment using a high precision micro-permeameter and a high-precision permeameter.
Each core was first saturated with 2% NaCl solution flooded with nitrogen gas and its permeability and porosity were recorded as K and phi, respectively. All samples were then treated with the base-fluid (distilled water) followed by a similar measurement of their permeabilities and porosities. The same cores were once again treated with a guar gum based porosities. The same cores were once again treated with a guar gum based solution ranging in concentration from 20 lbs/1,000 gal to 40 lbs/1,000 gal and their respective permeabilities and porosities were also computed after the treatment. Similar tests were run on the cores by adding 2% CaCl4 and 10% NaCl respectively on the different concentrations of guar. The results revealed that in all cases the core have been damaged and that the magnitude of the damage is not always proportional to the concentration of the guar gum; and in most cases the addition of 2% CaCl2 to the gelling agent solution gave better results than the addition of 10% NaCl. It can also be concluded that the treated guar gum will be more recommended for fracturing limestone formations, while its damage effect for sandstone formations is comparatively high.
The use of chemicals as gelling agents in hydraulic fracturing stimulations include both natural and synthetic products. These products fall into the class of high molecular-weight polymers. Synthetic chemicals used in gelling water are very costly and have a tendency to gel more rapidly and produce the same apparent viscosity at less concentration than the natural produce the same apparent viscosity at less concentration than the natural products such as guar gum. products such as guar gum.