How safe is our water?
Eagle Ford Shale in South Texas
May 6, 2011
While Gonzales County bustles with an oil and gas economic impact that is obvious to many, the Eagle Ford Shale has proven to be a jewel for South Texas.
Companies expand, businesses thrive – it’s all a part of this new oil boom that has taken South Texas by storm. But while we bask in the riches of this newfound gold, miles below us lies a question to our purest and precious resource – water.
Energy companies have taken to the common practice of hydraulic fracturing or “fracking” to extract shale gas. This practice has been around for more than 60 years but with the advancement of technology and horizontal drilling, it makes the procedure much more effective.
Shale rock formations have become an important source of natural gas in the United States. It is predicted by the year 2035, 60% of the production of natural gas will come from the U.S.
A horizontal well is comprised of both vertical and horizontal legs. The depth of the well varies with the location and properties of the gas-containing formations. In some cases, the well can extend more than a mile below the ground surface and the “toe” of the horizontal leg can extend almost two miles from the vertical leg.
In an effort to prevent contamination of surrounding subsurface formations, casings and cement are installed in the legs drilled. After the well is constructed, the targeted formation is hydraulically fractured to stimulate natural gas production.
To start the “fracking” process, large volumes of water are transported to the site. The water is mixed with chemicals and a propping agent. The resulting hydraulic fluid is pumped down the well under high pressures, causing the targeted formation to form fractures.
Within these fractures, natural gas is allowed to travel through and up the well for containment after the fluid is returned to the surface. The water returned to the surface is known as “flowback” or waste water and stored in tanks or pits before being transported for treatment, disposal, land application and/or discharge.
According to the Environmental Protection Agency field study program, much of the information regarding the identity and concentration of chemicals used in hydraulic fracturing fluids is considered by the industry to be “proprietary and, therefore, confidential”. This makes identifying the toxicity and human health effects associated with these chemicals difficult.
Large hydraulic fracturing operations require extensive quantities of supplies, equipment, water, and vehicles, which could create risks of accidental releases, such as spills or leaks. Surface spills or releases can occur as a result of tank ruptures, equipment or surface impoundment failures, overfills, vandalism, accidents, ground fires, or improper operations. Released fluids might flow into a nearby surface water body or infiltrate into the soil and near-surface ground water, potentially reaching drinking water aquifers.
Studies by Earthworks Texas Oil and Gas Accountability Project (OGAP) have shown that health problems have become central issues with many people complaining of odors, dizziness, nosebleeds, headaches and agitation.
According to OGAP, the Barnett Shale region in North Texas was the first shale area in the state to experience large-scale health issues that may have been directly related to gas drilling.
Though some studies have shown natural gases and methane gases escape in the fracturing process, which could further contaminate water sources. Energy companies take precautions abiding by EPA standards by reinforcing wells. Most cases, wells will be sealed with two casings and as much as two layers of cement to ensure safety.
But still the risk of hydraulic fractures combining with natural fractures that reach aquifers could lead to injections contaminating drinking water.
As much as five million gallons of water could be used per well in the fracturing process and some wells may be refracked several times over the life of each well.
EPA makes a practice of checking for well integrity on wells ensuring that our resource is safe. In cases of suspected drinking water contamination, EPA will investigate the role of natural and/or artificial pathways in leading to possible contamination through testing, field sample analysis and modeling.
Standard management practices recommend industries to clean up spills to be disposed or reused to protect human health and the environment.
While many factors could result in the practice of hydraulic fracturing, EPA monitors through tedious samples and investigations on wells across the U.S.
Industries ensure safety through EPA standards and the Texas Railroad Commission.