Mixed CMHPG and Synthetic Polymer Hydraulic Fracturing Fluid for High-Temperature Applications

Recent interest in deep low permeability formations demands growth in high-temperature hydraulic fracturing technologies. Conventional guar systems break down above 300°F and require higher polymer loadings to maintain thermal stability. Synthetic polymers designed for high-temperature utilize specialty monomers that are expensive. Individually, both these polymers are lacking in either performance or price. However, when these polymers are combined, they exhibit a synergistic interaction and produce a higher viscosity and better thermal stability than the individual polymer systems. Polymer solutions were prepared at a concentration of 20, 30 and 40 lb/1,000 gal, were crosslinked with a zirconium crosslinker, and broken with sodium bromate oxidizer, at 300°F. Testing was carried out in a HP/HT rheometer for viscosity, elasticity, salt influence, thermal stability, and breaking. A HP/HT see-through cell and an aging cell were used for visual assessment of proppant settling, and broken polymer residue respectively. Results show that the 20, 30 and 40 lb/1,000 gal mixed polymer fracturing fluid generates a stable crosslinked viscosity at 300°F and 100 s⁻¹ . Mixture containing 1:2, 1:1, and 2:1 (CMHPG: Synthetic) exhibit the most improvement in viscosity at 20, 30 and 40 lb/1,000 gal mixed polymer fracturing fluids, respectively. Results also show that synthetic polymer adds thermal stability while CMHPG improves the peak viscosity of the mix. The two polymers create a shared crosslinking network that enables reduced polymer loading applications. Moreover, the polymer mixture fracturing fluid exhibits good tunable delayed crosslinking, is able to carry proppant effectively at high temperature, and shows a controlled clean break with an oxidizer. Extensive experiments were pursued to evaluate the developed high temperature mixed polymer system for the first time. This mixture exhibits a positive interaction between the polysaccharide and polyacrylamide families and generates excellent thermal stability. Mixed polymer systems are a viable solution to combat the challenges currently faced in the industry such as the need to increase high temperature stability, high salt tolerance, and reduce the polymer loading used. Polymer mixture technology can potentially reduce material cost, simplify field operation, and reduce damage to the proppant pack and formation