Chemical Evolution of a High-Temperature Fracturing Fluid

Abstract

Reservoirs with bottomhole temperatures (BHT's) in excess of 250°F [121°q and penneabilities of less than 1.0 md are commonly encountered in drilling and completing geothennal and deep gas wells. Successful stimulation of these wells often requires the use of massive hydraulic fracturing (MHF) treatments. Fracturing fluids chosen for these large treatments must possess shear and thennal stability at high BHT's.The use of conventional fracturing fluids has been limited traditionally to wells with BHT's of 250 0 P [121°q or less. Above 250°F [121°q, high polymer concentrations and/or large fluid volumes are required to ,maintain effective fluid viscosities in the fracture.However, high polymer concentrations lead to high friction pressures, high costs, and high gel residue levels.The large fluid volumes also increase significantly the cost of the treatment. Greater understanding of fracturing fluid properties has led to the development of a crosslinked fracturing fluid designed specifically for wells with BHT's above 250~F [121°q. The specialized chemistry of this fluid combines a high-pH hydroxypropyl guar gum (HPG) solution with a high-temperature gel stabilizer and a proprietary crosslinker. The fluid remains stable at 250 to 350°F [121 to 177°q for extended periods of time under shear. This paper describes the rheological evaluations used in the systematic development of this fracturing fluid.In field applications, this fracturing fluid has been used to stimulate successfully wells with BHT's ranging from 250 to 540°F [121 to 282°q. Case histories that include pretreatment and posttreatment production data are presented.

Seawater-Based Fracturing Fluid: A Review

“…Buffers are used with polymers to ensure that the pH is optimal for polymer hydration. When the ideal pH is reached, a polymer achieves the highest possible viscosity. , Fracture fluid buffers typically consist of a combination of weak acids and weak bases, with the ratios of these ingredients being adjusted to obtain the required pH. The high-temperature viscosity of biopolymer solutions is positively correlated with basicity.…”

“…The high-temperature viscosity of biopolymer solutions is positively correlated with basicity. Buffer, polymer, and gel stabilizer mixtures have been tested as potential gel stabilizers for high temperatures (>250 °F) . The ideal pH for stability was chosen as the pH of the base fluid.…”

“…Buffer, polymer, and gel stabilizer mixtures have been tested as potential gel stabilizers for high temperatures (>250 °F). 82 The ideal pH for stability was chosen as the pH of the base fluid. Multiple transition metal cross-linkers were used on the optimized base fluid to find the best one.…”

A Crosslinkable Synthetic Polymer System for High-Temperature Hydraulic Fracturing Applications

“…One solution to produce these tight-gas reservoirs efficiently is to stimulate the wells with hydraulic fracturing. From a chemical perspective, the need for a thermally stable fracturing fluid that sustains molecular integrity at these temperatures is a step forward to address the HP/HT challenges (Shelley and Harris 2007;LaGrone et al 1985). These hot reservoirs are often deeply buried and fracturing fluids must transport proppant over longer distances at elevated temperatures.…”