Testing for Potential Contaminants Associated with Hydraulic Fracturing

The Fracking Process

A brief description of the fracking process is necessary to understand the rationale behind any strategy for sampling and analysis of drinking water from wells to determine if the water quality in the well is being affected by local fracking operations.  According to Wikipedia, hydraulic fracturing is “the widening of fractures in a rock layer caused by the high-pressure injection of chemicals with water.” It is this process that results in natural gas and oil to be recovered from deep shale deposits.  Typically, the wells involved in the fracturing process are in excess of 5000 feet deep.  The fractures occur when a fracturing fluid is pumped into the shale deposits under extreme pressure.  The wells are often horizontal to expand the area of fossil fuel recovery.  The fracturing fluid is primarily made up of water and sand.  The sand helps prevent the fractures from closing after the cracks in the shale form.  The sand is referred to as a “propping agent”.  Five million gallons of water or more may be required to fracture one horizontal well.  This does not include water used in subsequent fracturing of the same well.

Sources of Contaminants

Fracturing fluid

In addition to water and sand, other chemicals are added to the fracturing fluid.  There are a number of reasons for these chemical additives.  One of the concerns with these additives is that they may be contaminating groundwater.  Shale drillers are not required to disclose the chemicals used in the fracking fluid, and many of the formulations are proprietary in nature.  However, dozens of additives have been identified.  The Pennsylvania DEP has identified approximately 78 compounds and many of these pose health risks.  Some of these compounds fall into rather broad categories.  Biocides may be added to control bacterial growth that can result in hydrogen sulfide and associated corrosion.  Other corrosion inhibitors may be added to reduce pipe corrosion resulting from acids.  Various friction reducers may be used to increase pumping pressure.  Agents may also be used to improve the efficiency of the sand placement.  Glycols, glycol ethers, acids, bases, ammonium compounds, organometallic compounds containing antimony and chromium, and surfactants may all be included in the fracturing fluid.

Flowback water

A portion of the water that is injected into the ground returns to the surface.  This is called flowback water.  The amount of flowback varies, and it can be as little as 10% or essentially most of the water.  Typically, 20 - 40% of the water returns to the surface.  Initially, this water will primarily contain contaminants found in the fracturing fluid.  Secondary contaminants include contaminants naturally occurring in the ground.  Those contaminants include salts, heavy metals, and other toxic contaminants including radium 226. 

Production water

After the initial fracturing, water continues to return to the surface.  This is called production water.  The chemistry of this water begins to take on the characteristics of the shale formation, and contaminants will reflect the compounds found in the shale. Production water can exceed 1000 gallons per day.  The table below was compiled by Avner Vengosh at Duke’s Nicholas School reflecting their preliminary data over the first 20 days of a well operation.

Table 1. Preliminary data over the first 20 days of a well operation, Avner Vengosh, Duke’s Nicholas School (reproduced from http://www.nicholas.duke.edu/thegreengrok/frackingwater)

Standards:

*Primary drinking water

**Secondary drinking water

***Surface water quality criteria for chronic exposure

How does well contamination occur?

Contamination can occur in a number of ways including spills of fracking fluids, flowback, or production water.  Flowback and production water can be recycled; however, this tends to concentrate contaminants into what can become an unregulated sludge that can ultimately affect drinking water quality.  Otherwise, flowback and production water must either be treated or disposed of in some way.  Treatment is difficult because of the high concentrations of dissolved solids, which are difficult and expensive to remove.  Wastewater treatment facilities are generally not equipped to deal with such high levels of dissolved solids.  These solids can pass through the treatment plant and adversely affect downstream aquatic life and water quality.  Disposal is often performed by deep well injection.  Therefore the disposal method can affect aquifers and surface water supplies.  The fracking process itself can cause earthquakes that can potentially lead to aquifer and surface water contamination directly or indirectly.

Three Important Questions

With the fracking process becoming more widespread, concerned citizens are directing many questions to the water industry and laboratory community.  Three frequently asked and important questions are raised from concerned citizens to the laboratory community.  Those three questions are:

            When do I sample?

            How do I sample?

            What analytical tests should be run on my water?

When do I sample?

It is extremely important to sample prior to any shale drilling operations in the area.  Some naturally occurring contaminants may already be present in the well.  Every geographical and every geological formation is different.  Groundwater quality varies considerably depending upon many factors; each shale formation also varies considerably.  Sampling well water and having it analyzed prior to drilling operations serves as an important basis for comparison later after drilling operations are underway.  Without the baseline study, who is to say well contaminants were not already in the well prior to drilling?  It would be difficult to support a contention that the well was contaminated as a result of shale drilling.  The OEPA and the ODNR recommend samples are collected in different calendar seasons to establish a baseline that takes into account variability in water quality.

Re-evaluation of the well at some periodic interval is suggested.  There is no hard and fast requirement for this, but water quality may change before it becomes evident through taste, odor, or appearance.  Whether follow-up sampling and analysis is conducted after 6 months, 12 months, or some other specified time, routine monitoring should be part of a well monitoring program. 

Finally, sampling is warranted in cases where there are obvious changes in taste, odor, or appearance.  It is at this juncture when the baseline study becomes important because it serves as a basis for comparison of water quality parameters.

How do I sample?

Water sampling should be performed by experienced personnel who have been trained to collect water samples.  Properly trained personnel will ensure samples are collected properly, with adequate volumes, and are in the appropriate containers with proper preservation.  They will also ensure the sampling event is properly documented.  In our business, it is often said “an analysis is only as good as the sample collected.”  If there were an issue that involved litigation, analytical work could be invalidated for a number of reasons, including: headspace in volatiles vials, improper preservation, improper sample handling, incomplete chain of custody, transportation issues, and improper sample collection techniques.  Even the point of sampling could be called into question.  Samples should be collected directly from the well and prior to any filters, softeners, and other forms of treatment.  It is best to leave the sampling to the professionals.

What analytical tests should be run on my water?

There are many different lists available.  Table 2 identifies the analytes recommended by the OEPA and ODNR for water well sampling before oil and gas drilling.  The same tests should be performed in follow up testing.   Samples should be submitted only to an EPA certified laboratory.  Submitting samples to a laboratory not certified for every analyte for which certification is available will result in data that will not be useful in any investigative or legal proceedings.

Table 2.  Recommendations for Water Well Sampling Before Oil & Gas Drilling

*Include with Tier 1 if laboratory can analyze for methane.

Other analytes that do not appear on in the table above, but could provide additional insight into water quality changes over a period of time include arsenic, total organic carbon, oil & grease, nitrate, surfactants, turbidity, lead, fluoride, antimony, beryllium, copper, and nickel.

The choice of which list or group of tests are performed is basically up to the individual well owner, and is often a function of cost.  Obviously, the more comprehensive the baseline studies, the better.  Each compound or group of compounds reflects contaminants potentially found in fracking fluid, flowback water, or process water.

Ultimately, the questions people want answered are “is my water safe to drink?” and “has the drilling operations affected my water quality?”  The purpose of the baseline is to provide a comparison between before and after drilling operations.  Significant test result increases in analytes, especially dissolved solids and the gases (especially methane) might be indicative of contamination issues.  To learn more about contaminants and limits that can help answer questions regarding the safety of the water, visit the USEPA website.