The management of produced water presents many challenges and can pose significant costs to operators. Operators are careful to manage produced water in ways that protect surface and groundwater resources. Whenever possible, operators seek to reduce future demands for freshwater by examining both traditional and innovative approaches to reuse or recycle by using in other production processes. Current techniques include a variety of methods such as underground injection, treatment and discharge, evaporation, reuse and recycling.
Underground injection has historically been the primary disposal option for produced water by the natural gas and oil industry. After produced water is separated from the gas, saltwater disposal wells (SWDs) are used to return the water underground into porous rock formations similar to those from which it came. SWD wells are a proven technology. The disposal of produced water through use of this method is a monitored, safe and necessary practice which is overseen and inspected regularly by the Department of Natural Resources Office of Injection and MiningRailroad Commission of Texas (RRC) in the Haynesville Shale region.
Chesapeake uses saltwater disposal wells (SWD wells) for the disposal of a portion of produced water in West Virginia. After produced water is separated from the gas, it is returned deep within the earth from where it came using SWD wells. A type of Environmental Protection Agency (EPA)-classified, Class II injection well, SWD wells are highly regulated and commonly used by the natural gas and oil industry to dispose of water generated during production.
SWD wells are a proven technology and the safest method of disposal today. The disposal of produced water through use of this technology is a monitored, safe and necessary practice which is overseen and inspected regularly by the EPA.
“When wells are properly sited, constructed and operated, underground injection is an effective and environmentally safe method to dispose of wastes.” — Environmental Protection Agency (EPA)
A SWD well is considered a “Class II” injection well by the EPA. SWD wells are highly regulated and commonly used by the natural gas and oil industry to dispose of water generated during production. Tank batteries are present at each drillsite for the storage of water resulting from natural gas production.
The Department of Natural Resources Office of Injection and Mining regulates disposal wells and their construction in the Haynesville Shale region. The RRC regulates disposal wells and their construction in East Texas. These regulations are the industry standard and are considered safe and effective. Still, Chesapeake exceeds the commission’s standards by constructing SWD wells with multiple layers of protective steel casing and cement that are specifically designed and installed to protect groundwater and to ensure that the producing zone is protected from overlying formations. The layers of protection are:
The EPA, Region 3 and the West Virginia Department of Environmental Protection regulate disposal wells and their construction in West Virginia. The EPA’s federal regulations are the industry standard. Chesapeake meets or exceeds these standards when constructing SWD wells, including multiple layers of protection to effectively isolate the injected water from surrounding drinking water aquifers1. These layers of protection include a number of factors such as:
- Surface casing is run 100 feet below the lowest usable source of underground drinking water
- Surface casing is run to a depth well below all freshwater aquifers, typically to a depth of 1,800 feet below the surface
- A layer of cement holds the surface casing in place
- Production casing runs through approximately one to 1.5 miles of rock between the freshwater aquifers and the intended formation
- Production casing runs through several thousand feet of rock between the freshwater aquifer and the injecting formation
- An additional layer of cement holds the production casing in place
- A packer is installed at a minimum of 3,000 feet below the deepest known freshwater zone
- A packer is installed deep within the casing to isolate the injection zone
- Steel tubing is put in place down the entire length of the SWD well
- An internal plastic coating is added to the tubing to prevent corrosion
Thousands of feet of impervious rock exists between the injected water and the groundwater located in freshwater aquifers, making it virtually impossible for any produced water to come into contact with these zones.
The mechanical integrity of SWD wells is also regularly tested, and the pressure in the well is monitored continuously to ensure that all of the disposed water reaches the intended formation.
Strategically located SWD wells can reduce the miles trucks must travel in order to dispose of produced water. Connecting water pipelines from gas wellsites to SWD sites would lessen truck traffic even more dramatically, reducing emissions, traffic noise, traffic congestion and road repairs. This would result in fewer emissions, improved air quality and increased safety in LouisianaEast Texas.
In addition, the mechanical integrity of a SWD well is tested regularly, and the pressure in the well is monitored continuously to ensure that all of the disposed water reaches the injecting formation.
The overwhelming majority of injected fluid is oilfield brine, which is also called produced water. Produced water comes up simultaneously with the production of natural gas. However, small quantities of substances used in the drilling, completion and production operations of a well may be mixed in with the produced water. Some of these materials include small amounts of drilling mud, fracture fluids and well treatment fluids. Also, since the produced water is associated with crude oil and natural gas, small amounts of naturally occurring hydrocarbons may also be found.
For more information about SWD wells, contact the following organizations:
To learn more about the topics on this page, please contact the following organizations:
- Clean Air Technology Hotline
- Code of Federal Regulations
- Environmental Protection Agency
intevras.com | 512-538-2668
- National Response Center Hotline
- Natural Gas Regulations
naturalgas.org | 202-326-9300
- Louisiana Department of Natural Resources
- Railroad Commission of Texas
rrc.state.tx.us | 877-228-5740
- U.S. Department of Energy
eia.doe.gov | 202-586-8800
- U.S. Department of Transportation
dot.gov | 202-366-4000
- U.S. Government Printing Office
1“Hydraulic fracturing considerations for natural gas wells of the Marcellus Shale” Arthur, Bohm, et al presented to Groundwater Protection Council, September 2008. pg 15