Oil and gas wells in the huge Eagle Ford shale discovery in South Texas will require hydraulic fracturing or a “frac job” to complete. According to Chesapeake Energy’s website, drilling a horizontal well in the Eagle Ford shale uses well over six million gallons of water. Other estimates of water use by Eagle Ford shale drilling put this amount even higher. Despite much media attention focused on “frac jobs”, this process has been proven to be generally very safe when regulated. In Texas the procedure has been used for over fifty years without a case of groundwater contamination. Despite that fact, Eagle Ford shale frac water contains toxic chemicals such as benzene, and must be disposed of properly after the process has been completed. Much of the water used remains in the Eagle ford shale formation after fracking. What comes back during the flowback and production process must be disposed of. Frac water from Eagle Ford shale wells will mostly be disposed of in disposal wells. These same wells are used to dispose of naturally occurring saltwater that is often produced with oil and gas. There are over 50,000 permitted injection and disposal wells in Texas. Below is a photo of a saltwater injection facility near Midland from Energy Industry Photos.
Trucks waiting to unload at a saltwater disposal facility.
Trucks generally transport used frac water or produced saltwater to a facility such as the one seen above, where it is pumped deep underground in a disposal well. Other wells, known as injection wells, use this type of waste water to help produce oil and gas in marginal reservoirs by forcing it out. This is known as secondary recovery. There are a handful of companies who specialize in cleaning up used frac water so that it can be reused on the surface instead of being injected in disposal wells. So far the technology of cleaning used frac water has not been widely implemented by oil and gas companies do to its cost.
Below is an illustration of an injection or disposal well. For more info on Texas law regarding disposal wells for Eagle Ford shale frac water see Texas RRC
Eagle Ford shale water use is going to be one of the hottest issues in the region in the next few months. Literally thousands upon thousands of oil and gas wells will be drilled in the Eagle Ford shale and each will require millions of gallons of valuable water. In an area known for droughts and scarcity of water, the fact of that this much valuable water will be pumped out, used and then disposed of forever in deep injection wells is something every South Texas resident should be concerned about. The Carrizo Wilcox aquifer spans a large area across South Texas and provides drinking water for towns such as Cotulla Texas and many other communities, in addition to ranches and farms which depend on it for agricultural use. This aquifer is already being depleted much faster than it is being recharged and water takes literally hundreds of years to move across the sandstone formation from the recharge zone.
Below is an excerpt of a paper found on the AAPG website about Eagle Ford shale water use
Drilling in the Eagle Ford shale is about to consume literally billions of gallons of water over the next few years. Once it is pumped out, it is gone from slow recharge aquifers such as the the Carrizo – Wilcox forever. We desperately need domestic sources of oil and gas, however water use in the Eagle Ford shale drilling area needs to be closely monitored. Water in the Carrizo – Wilcox aquifer is a valuable resource to South Texas residents and something must be done to ensure that this resource remains for present and future generations. Counties, towns, and property owners should not be blinded by the millions of dollars of Eagle Ford shale oil revenue they will be getting and make sure that groundwater sources such as the Carrizo Wilcox, Queen City sand and other aquifers are used responsibly. The truth is, you can live in South Texas without oil, but you can’t live there without water. The issue is being investigated by a number of private and state agencies, such as the Texas Water Development Board. Some of those private studies showing a minimal impact on the Carrizo Wilcox aquifer are now outdated, since even smaller oil and gas well spacing may be allowed in the play, thus more wells drilled and fracked than was initially forecasted.
Note: Some groundwater that is pumped out will be reused to frac other wells, but due to logistics issues such as “where will the next well to be fracked be located, ready, etc” storing, transporting and treating millions of gallons of used frac water for re-use may be impractical for some oil companies. This is because the Eagle Ford shale covers a huge undeveloped swath of South Texas, which consists of large ranches with miles of bad roads. It will often be more economical to truck flowback water to the nearest disposal well and drill a new Carrizo – Wilcox water well to obtain water for the next frac job. Once it is removed from the aquifer, it will not be put back. Recharge of the Carrizo aquifer is a very slow process that takes hundreds of years.
For more about the process of hydraulic fracturing as used in the Eagle Ford shale and other areas, see What Is Hydraulic Fracturing or Frac Jobs?