One of the most misunderstood parts of hydraulic fracturing is what gets pumped down the well. The reality is straightforward: frac fluid is mostly water and sand. A common slickwater formulation is roughly 90% water, about 9.5% sand (proppant), and around 0.5% additives. Across different fluid designs the additive fraction generally falls between 0.5% and 2%, with water and sand making up the remaining 98–99%.
A low-viscosity frac fluid that is mostly water with a friction reducer added so it can be pumped at high rates. Slickwater is the workhorse fluid for shale fracturing.
What the additives do
Although they make up a tiny share of the total volume, the additives are what make the fluid work. A typical job uses only a handful — commonly between 3 and 12 distinct additives — each with a defined role:
- Friction reducers let the fluid be pumped at high rates without excessive pressure loss in the pipe.
- Biocides kill bacteria that would otherwise corrode equipment or sour the reservoir.
- Scale and corrosion inhibitors protect the casing and tubing from mineral buildup and metal loss.
- Gels and crosslinkers thicken the fluid so it can carry more proppant in certain designs.
- Surfactants reduce surface tension and help the well clean up and flow back.
- pH adjusters and dilute acid control chemistry and clean perforations near the wellbore.
In the United States, the chemical additives used on each fracked well are publicly disclosed through FracFocus (fracfocus.org), the national hydraulic fracturing chemical registry.
Transparency and the "secret chemicals" myth
A persistent myth is that frac fluid is a dangerous brew of secret chemicals. In fact the fluid is about 99% water and sand, and the additives used are disclosed well by well through FracFocus, the national registry operated for that purpose. Many additives are familiar from everyday products — friction reducers, for example, share chemistry with materials used in food and cosmetics.
That isn't to say the chemicals are harmless in concentrated form; they are handled as industrial materials at the surface, which is exactly why spill prevention and proper well cementing matter. But the picture of a fluid that is mostly secret toxins is inaccurate. Understanding the actual composition — water, sand, and a short, disclosed list of purpose-built additives — is the starting point for any honest conversation about fracking.
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Frequently asked
Only about 0.5% to 2% by volume. The other 98–99% is water and sand. A common slickwater mix is roughly 90% water, 9.5% sand and 0.5% additives.
In the U.S., operators disclose the additives used on each well through FracFocus at fracfocus.org, the national hydraulic fracturing chemical disclosure registry.
Slickwater is a low-viscosity frac fluid that is mostly water with a friction reducer added so it pumps easily at high rates. It is the most common fluid type for fracturing shale.