Maximizing Performance of Residue-Free Fracturing Fluids Using Nanomaterials at High Temperatures

Abstract

Abstract Polysaccharide-based fluids such as guar fluids are commonly used in hydraulic fracturing operations, primarily because of their abundance, relative low cost, and capability to work at up to 350°F when formulated at high pH. However, one notable disadvantage for most guar is the insoluble residue which tends to cause permeability reduction. Another disadvantage for using guar-based fluids at high pH is the tendency of forming divalent ion scales at high pH. In general, thermally stable synthetic polymers, such as acrylamide based polymers are considered to be residue-free. They can be used for preparing fracturing fluids around 300-450°F or more. However, high dosage of acrylamide based polymers may still cause formation damage due to factors such as incomplete degradation. This paper demonstrates the advantage of using selected nanomaterials to enhance the thermal stability of the crosslinked synthetic fluids and to reduce the polymer loading. With addition of a small amount of nanomaterials (e.g. 0.02wt%), the polymer loading used at temperatures 300-450°F can be reduced dramatically compared to other existing commercial products. This paper presents results from rheological studies which demonstrate superior viscosity performance and excellent thermal stability of this novel fluid system enhanced with the nanomaterials at this high temperature range. For example, at 30 pounds per one thousand gallons (pptg) polymer dose, the fluid viscosity stays above 500cP (at 40 s-1 shear rate) at 350°F for more than 3 hours. This fracturing fluid system has therefore shown sufficient proppant carrying and transporting capability. The fluids can be efficiently broken to allow for good cleanup using oxidative breakers. Proppant-pack conductivity tests for a 300°F fluid formulation gives 83% regained perm proving the low damaging potential of this type of fluids. Using low loading of residue-free polymer therefore results in better cleanup, reduced formation damage, and enhanced production rates. The nanomaterial-enhanced fracturing fluid system based on the synthetic acrylamide copolymers demonstrates the unforeseen combination of a number of advantages including low polymer loading, excellent high-temperature performance, and high retained permeability.