Vitamin C: An Environmentally Friendly Multifunctional Additive for Hydraulic Fracturing Fluids

Abstract

Abstract There exists a need for high temperature fracturing fluids as we expand exploration into deeper, lower permeability, and hotter formations. Fracturing fluid stability depends on two main bonds: the crosslinker to polymer bond and the monomer to monomer bond. To preserve the crosslinker to polymer bond, a proper crosslinker with a suitable delay additive is typically utilized. On the other hand, the monomer to monomer bond is challenging to protect since it’s susceptible to a variety of factors with the main culprit being oxygen radical attacks. Consequently, the most common high temperature stabilizers used are oxygen scavengers such as sodium thiosulfate or sodium sulfite. Unfortunately, both additives create their own issues. Sodium thiosulfate is known to degrade at high temperature to generate H2S, while sulfites generate sulfates that end up causing inorganic scale precipitation or feeding sulfate reducing bacteria creating another source of H2S in the reservoir. Additionally, Sodium thiosulfate is a high pH additive which can cause formation damage through fines migration and precipitation of hydroxides. Vitamin C is renowned for its antioxidative and oxygen scavenging properties throughout many industries. It is commonly used as an extremely cheap supplement to boost the immune system and as a food preservative to increase shelf life. Moreover, it has an acidic pH and offers a chemical structure capable of delaying crosslinking reactions. For that reason, this work aims to study the influence of Vitamin C as a multifunctional additive in fracturing fluids. The tests mainly utilized the high-pressure/high-temperature (HPHT) rheometer. The performance of Vitamin C was assessed with a guar derivative at temperatures between 250-300°F for 1.5 hours. Moreover, zeta potential and coreflood were used to evaluate the formation damage tendencies of using this additive. The results showed that the use of Vitamin C was able to provide a pH reduction, crosslinking delay, and enhance the high temperature stability of fracturing fluids. Zeta potential and coreflood experiments showed that clays were more stable at lower pH conditions minimizing fines migration. Vitamin C is a cheap and readily manufactured environmentally friendly additive that offers solutions to the use of fracturing fluids at high temperatures. Utilizing it not only offers oxygen scavenging ability, but also replaces additives that lower pH and provides crosslinking delaying properties.