Hydraulic fracturing fluid, or fracking fluid, is an engineered mixture injected deep underground to release trapped hydrocarbons like natural gas and oil. The fluid is pumped under immense pressure to force open rock formations miles beneath the surface. Its purpose is to create and maintain a network of fissures, allowing oil and gas to flow more freely to the wellbore and the surface.
The Primary Components: Water and Proppant
The overwhelming majority of hydraulic fracturing fluid, typically over 98% of its total volume, is composed of just two main ingredients: water and a solid material called proppant. This high-volume composition means the chemical additives make up only a tiny fraction of the mixture.
Water generally accounts for 85% to 95% of the total fluid volume, making its sourcing and disposal a significant logistical challenge. Water serves as the primary fluid carrier, generating the hydraulic pressure needed to fracture the rock. It also transports the proppant deep into the newly created fractures.
The solid material, known as proppant, is typically specialized sand, though ceramic beads may also be used. Proppant generally makes up between 4% and 9.5% of the fluid volume. Its function is mechanical, acting to “prop” open the fractures after the high injection pressure is relieved.
By holding the fissures open, the proppant creates a permeable pathway that allows hydrocarbons to migrate toward the well. Without this solid support structure, the fractures would close, severely reducing the process efficiency. The remaining small percentage of the fluid volume contains the highly specialized chemical additives.
Categorizing the Functional Chemical Additives
The chemical additives represent the remaining fraction of the fluid, usually ranging from 0.5% to 2% of the total volume. These compounds are engineered to ensure the efficiency and integrity of the fracturing operation deep underground. A typical fracturing job may use three to twelve different chemical products, selected for the specific conditions of the well.
Friction Reducers
Friction reducers are added to allow the fluid to be pumped at high rates and pressures with less energy. Additives such as polyacrylamide decrease the friction between the fluid and the interior of the steel piping. This reduction is necessary to maintain a stable, high-volume flow rate over the distances the fluid must travel.
Gelling Agents and Breakers
This specialized group controls the fluid’s viscosity. Gelling agents, like guar gum, thicken the water to suspend and transport the proppant deep into the fractures. Once the proppant is placed, chemical breakers, such as ammonium persulfate, are introduced to rapidly reduce the fluid’s viscosity. This allows the thin fluid to flow back out of the well, leaving the proppant behind in the open fissures.
Corrosion Inhibitors
Corrosion inhibitors protect the metal casing and pumping equipment from degradation. Compounds like citric acid are used to prevent damage from acidic fluids or other corrosive elements found downhole.
Biocides (Bactericides)
Biocides protect the wellbore from biological contamination. Water introduced into the well can carry bacteria that multiply, creating biofilms that clog the fractures or produce corrosive byproducts. Biocides, such as glutaraldehyde, are added to prevent this microbial growth and preserve the long-term flow capacity.
Scale Inhibitors
Scale inhibitors prevent the formation of mineral deposits that can clog the system as water flows back from the rock formation. Deep underground water often contains high concentrations of dissolved minerals, which can precipitate out. Scale inhibitors, such as ethylene glycol, ensure the smooth flow of hydrocarbons and water by keeping these mineral salts in solution.
Transparency and Public Disclosure of Ingredients
The composition of the fracturing fluid is subject to various disclosure requirements across operating regions. Many jurisdictions now require operators to report the chemicals used in a fracturing operation to a public database system. These reporting systems are designed to offer transparency regarding the substances introduced into the subsurface environment.
The mechanisms for disclosure often contain provisions that allow companies to withhold the identity or specific concentration of certain chemicals. This exemption is typically invoked under the claim of “trade secrets” or proprietary business information, protecting the specific formulation of a chemical product. This means that while the majority of chemicals are disclosed, a small percentage may be listed generically or withheld from the public record.
Studies examining these disclosure databases have found that a large percentage of reported wells include at least one chemical component designated as a trade secret. This proprietary withholding creates challenges for public health officials and researchers attempting to conduct comprehensive risk assessments.