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.” — EPA
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
- 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
- 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
- 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
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.
Water Transportation Options
Produced water from wellsites is trucked to SWD well for disposal. Water trucks can transport between 3,000 to 5,000 gallons of water per load, depending on the size of the vehicle. Truck traffic, like the amount of water produced from wells, drops significantly in a relatively short amount of time. After three months of production, less than one truck per week per well is normally needed to carry water offsite and the volume of water continues to decline during the life of the well.
Strategically located SWD wells can also help reduce the miles trucks must travel in order to dispose of produced water. Since trucks must be used to transport produced water from wellsites to disposal locations, the number and location of SWD wells has a direct bearing on the number of vehicle miles traveled for natural gas production. Strategically located disposal wells would lessen truck traffic and reduce emissions, traffic noise, traffic congestion and road repairs. This would result in a smaller impact to air quality and increased road safety for the people of West Virginia.
References
To learn more about the topics on this page, please contact the following organizations:
Sourcing Reference:
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
2 US Department of Energy - “Modern Shale Gas Development in the United States. A Primer” – Page 70