>>Dr. Robert Puls: The next table is information taken from FracFocus, a voluntary chemical
registry maintained by the Groundwater Protection Council. It lists the chemicals and the amounts
used on a particular frac job. The information was provided by an operator and lists the
component, ingredient, purpose, and amount as a percent composition by mass for the total.
As can be seen, freshwater is the main ingredient with some recycled water added. Sand is the
next largest ingredient, followed by acid and friction reducer. In general, it is the
ingredients with the lowest overall mass that present the most concern from an environmental
perspective. This includes the corrosion inhibitors, biocides, and scale inhibitors.
So, what is the purpose of the chemicals? Each one has a specific purpose. Acid removes
near well damage and cleans up perforations of cement prior to the actual injection of
the fracturing fluid. Biocides control bacterial growth in fluids to prevent clogging and reduced
performance. Corrosion inhibitors prevent corrosion of the pipe. Friction reducers decrease
pumping friction in the pipe and in the created fractures. Gelling agents improve proppant
placement and produce a higher viscosity for proppant delivery.
The next table is again from the same well but now shows the toxicity of the ingredients.
One measure of toxicity listed in the table is the European Union/Swiss Poison Class,
which is a numeric value from 1-5. The smaller the value, the more toxic the ingredient.
A low value means the ingredient is toxic in small quantities. Three is the lowest value
in this table and is attributed to Petroleum Distillates, 2-Butoxyethanol, Quaternary Ammonium
compounds, and Methanol -- friction reducers, corrosion inhibitors, biocides, and scale
inhibitors. Probably the biggest concern for these ingredients and the environment is handling
of the concentrated forms on the surface in terms of transport to the well pad and on-site
handling of the bulk chemicals during mixing and injection.
The next table explains, in a little more detail, the EU/Swiss Poison Class scheme.
This next table shows where these same chemicals are used in other industries and in other
applications. What's shown here are the components on the left (again, particularly those that
cause the most environmental concern), the actual ingredients in those components, and
then where these same ingredients are used in other products. So for instance, with friction
reducers, these things are often used in water treatment and in paint supplies. Iron control,
citric acid, is used commonly as a food additive. Corrosion inhibitors, things like ethylene
glycol, dimethyl formamide, isopropanol are used in a variety of products, including automotive
anti-freeze, production of acrylic fibers and plastics, pharmaceutical applications,
gasoline additives, precursors to perfume, solvents in paints, whiteboard cleaners, and
cosmetics. Biocides are commonly used in alcoholic drinks, in disinfectants, and in sterilization
for medical equipment.